Cooler Leaf - on Heat Energy Storage & Ice Packs

I've searched around a fair bit on these matters, and I think I might be onto something. I live in Fresno, where heat is a big concern for EVs like the Leaf. My 2013 Leaf S usually starts a morning at 6 temp bars, ends on the high end of 7, was even driving around on 8 not too long ago. No fast chargers (probably for good reason now that I consider it). Very few places other than home to charge. It's all environmental heat, and that poses an interesting set of conditions for experimenting.

The big problem is that the battery stores a lot of heat energy - a sort of napkin-sketch example would be to say it probably has 1 kWh of energy stored as a heat differential between the environment and the battery temp at night. So even though it's 70F outside, the battery might only get down from 100F to 90F by the morning, then back to 100 where it's driven and cycled, rinse and repeat. Not so great for lithium chemistry.

I also found that the motor/controller under the hood has a *very* bad effect on this, caused by its cooling system behavior. I went out to check on it today, after it'd been charging from 20% to 90% at 4kW, and found that under the hood was hotter than I'd ever felt it before! I'm talking ICE engine hot. But the fan wasn't running! I left the hood open and ran the A/C at 82 for about 20 minutes, which ran the cooling fans constantly with the A/C cycling on and off (slowly, with low heat output/power consumption). Only way I knew to get the fans to run. It cooled off the block to lukewarm temp, but during that time, you wouldn't believe how much heat billowed out from the hood before the air was cool again.

All that heat was typically stored in the car from night to night, which in turn transfers to the battery (which I'd think would be cooled by the chilly motor components). I would think the cooling fan would be running, at least at a low speed, while charging. Seems pretty obvious to me - laptops have done it from the start, even modern desktop PCs vary their fans as needed. With the concerns about battery heat and longevity, how could Nissan forget this important detail?

So, what I've been doing lately - before discovering the motor heat issue - I've been playing with placing ice-chest freezer blocks in the emergency disconnect switch box. There's a fairly large space in there to put them, and since cold air falls while heat rises, the cold air circulates and conducts through the metal of the battery pack, rather effectively using the ice to cool the battery overnight. That day I came home with 8 bars was when I started playing with the concept, and the next morning, I started off with 6 bars, only hitting 7 halfway through the day. It's only been a week, so I don't have much data to play with... but I figured I should get a topic and discussion going on this.

Anyone know how to kick that cooling fan on while charging? Maybe a command through the OBDII interface through the Leaf Spy app?

You might get substantially more cooling by blowing air through the ducts that cool the pack *backwards*, from the rear to the front. That would allow you to start with air as cool as possible. You could always place some large bottles of frozen water just behind the fan(s) to drop the temp of the incoming air. I built a portable car A/C unit years ago, when my First Civic's A/C inevitably failed. A couple of large freeze blocks had a substantial cooling and dehumidifying effect (I used a cooler for the housing, and let water collect in the bottom, to be drained).

FalconFour said:

My 2013 Leaf S usually starts a morning at 6 temp bars, ends on the high end of 7, was even driving around on 8 not too long ago.
...
I also found that the motor/controller under the hood has a *very* bad effect on this, caused by its cooling system behavior. I went out to check on it today, after it'd been charging from 20% to 90% at 4kW, and found that under the hood was hotter than I'd ever felt it before! I'm talking ICE engine hot. But the fan wasn't running! I left the hood open and ran the A/C at 82 for about 20 minutes, which ran the cooling fans constantly with the A/C cycling on and off (slowly, with low heat output/power consumption). Only way I knew to get the fans to run. It cooled off the block to lukewarm temp, but during that time, you wouldn't believe how much heat billowed out from the hood before the air was cool again.

All that heat was typically stored in the car from night to night, which in turn transfers to the battery (which I'd think would be cooled by the chilly motor components). I would think the cooling fan would be running, at least at a low speed, while charging.

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Interesting... I'm not usually around my Leaf when it's charging (usually down in an underground garage @ work) but I've never observed any of the fans running while charging either. And yes, I know what you mean about the under hood temps although, mine charges indoors, so I'm sure it's nowhere near as bad.

Haha, that's funny about running the AC @ 82 degrees. For me, since I have a '13 SV w/hybrid heater (w/heat pump), it's quite funny to run the heater at high temps. The fans run and it's just cool air coming thru the radiator to the PDM stack. If you'd gotten an SV or SL, that'd be your solution...

There is enough charger waste heat transferred form the radiator to no need a fan running. The hood also acts as a conductor of the heat and this is not being transferred to your pack so it's senseless to worry about. The thermal mass of the back is great during charging and a fan on the radiator has no relation to pack heat, if you move it faster from the engine compartment it will just heat to a garage garage faster. if it is outside it is moot and inside it is moot as well since you would need to vent a garage not the car. The ice is a pointless waste of energy consumed for no practical gain. The inverter and motor you mention have no involvement here since this is waste charger heat. Effectively anything you are doing will have no impact on your pack temp other than parking on a cooler surface or location.

But surely for the cooling fans to cool the motor you'd have to have the liquid cooling system active, and that only operates when the car is in motion?

The fans run with AC because the condenser at the front has to be cooled else the AC won't work.

The only way to cool the motor/charger is to pass cold air over it. This is actually quite easy to do - set your heating on rather than your AC on (I assume your 2013 has a heat pump?). With AC, the radiator acts as a condenser and has to eject heat, whereas with the heating on the radiator acts as an evaporator and draws heat out of the air. You'd then be fanning colder air over the motor/charger.

You could get some big mains operated fans and put them flat on some castors, you can roll it under the car and ventilate. This will prevent heat build up in the charger system and avoid heat soak.

FalconFour said:

I've searched around a fair bit on these matters, and I think I might be onto something. I live in Fresno, where heat is a big concern for EVs like the Leaf. My 2013 Leaf S usually starts a morning at 6 temp bars, ends on the high end of 7, was even driving around on 8 not too long ago. No fast chargers (probably for good reason now that I consider it). Very few places other than home to charge. It's all environmental heat, and that poses an interesting set of conditions for experimenting.

The big problem is that the battery stores a lot of heat energy - a sort of napkin-sketch example would be to say it probably has 1 kWh of energy stored as a heat differential between the environment and the battery temp at night. So even though it's 70F outside, the battery might only get down from 100F to 90F by the morning, then back to 100 where it's driven and cycled, rinse and repeat. Not so great for lithium chemistry.

I also found that the motor/controller under the hood has a *very* bad effect on this, caused by its cooling system behavior. I went out to check on it today, after it'd been charging from 20% to 90% at 4kW, and found that under the hood was hotter than I'd ever felt it before! I'm talking ICE engine hot. But the fan wasn't running! I left the hood open and ran the A/C at 82 for about 20 minutes, which ran the cooling fans constantly with the A/C cycling on and off (slowly, with low heat output/power consumption). Only way I knew to get the fans to run. It cooled off the block to lukewarm temp, but during that time, you wouldn't believe how much heat billowed out from the hood before the air was cool again.

All that heat was typically stored in the car from night to night, which in turn transfers to the battery (which I'd think would be cooled by the chilly motor components). I would think the cooling fan would be running, at least at a low speed, while charging. Seems pretty obvious to me - laptops have done it from the start, even modern desktop PCs vary their fans as needed. With the concerns about battery heat and longevity, how could Nissan forget this important detail?

So, what I've been doing lately - before discovering the motor heat issue - I've been playing with placing ice-chest freezer blocks in the emergency disconnect switch box. There's a fairly large space in there to put them, and since cold air falls while heat rises, the cold air circulates and conducts through the metal of the battery pack, rather effectively using the ice to cool the battery overnight. That day I came home with 8 bars was when I started playing with the concept, and the next morning, I started off with 6 bars, only hitting 7 halfway through the day. It's only been a week, so I don't have much data to play with... but I figured I should get a topic and discussion going on this.

Anyone know how to kick that cooling fan on while charging? Maybe a command through the OBDII interface through the Leaf Spy app?

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Please keep testing! While I do not have high ambient temps to worry about here in the Pacific Northwest, I do experience HIGH pack temps on occasion while DC quick charging repeatedly on road trips. A solution to cool the pack through the HV access would be great.

donald said:

But surely for the cooling fans to cool the motor you'd have to have the liquid cooling system active, and that only operates when the car is in motion?

The fans run with AC because the condenser at the front has to be cooled else the AC won't work.

The only way to cool the motor/charger is to pass cold air over it. This is actually quite easy to do - set your heating on rather than your AC on (I assume your 2013 has a heat pump?). With AC, the radiator acts as a condenser and has to eject heat, whereas with the heating on the radiator acts as an evaporator and draws heat out of the air. You'd then be fanning colder air over the motor/charger.

You could get some big mains operated fans and put them flat on some castors, you can roll it under the car and ventilate. This will prevent heat build up in the charger system and avoid heat soak.

Click to expand...

The topic here is charging heat not motor or inverter heat and they have nothing to do with the pack. In addition the car does not need to be moving to cool the charger which is cooled by a pump that circulates water during charging and is not contingent on fan use nor does it have any relevance on pack cooling. Adding additional cooling for the charging or the inverter/motor is pointless. Non of this adds any benefit to the pack temp or has any value. This thread is based on a fundamental misunderstanding of the LEAF systems and a proposed solution that has no relevance on pack cooling. Heat is not soaking from the engine compartment to the pack in any meaningful manner.

FalconFour said:

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All that heat was typically stored in the car from night to night, which in turn transfers to the battery (which I'd think would be cooled by the chilly motor components).

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Not sure I follow. The motor compartment and battery case seem fairly well separate. Not much potential for heat transfer.

I would think the cooling fan would be running, at least at a low speed, while charging. Seems pretty obvious to me - laptops have done it from the start, even modern desktop PCs vary their fans as needed. With the concerns about battery heat and longevity, how could Nissan forget this important detail?

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I'd be surprised if they "forgot". Part of "varying fans as needed" is to not use them at all when not needed. No doubt the charger has some thermal sensor that would either invoke the fan, or terminate charging at some predetermined temperature(s) to keep the charger's electronics within a safe range. That your charger continues to operate and we don't hear increased OBC failures with age, suggests it's probably being adequately cooled.

Nubo said:

FalconFour said:

…
All that heat was typically stored in the car from night to night, which in turn transfers to the battery (which I'd think would be cooled by the chilly motor components).

Click to expand...

Not sure I follow. The motor compartment and battery case seem fairly well separate. Not much potential for heat transfer.

I would think the cooling fan would be running, at least at a low speed, while charging. Seems pretty obvious to me - laptops have done it from the start, even modern desktop PCs vary their fans as needed. With the concerns about battery heat and longevity, how could Nissan forget this important detail?

Click to expand...

I'd be surprised if they "forgot". Part of "varying fans as needed" is to not use them at all when not needed. No doubt the charger has some thermal sensor that would either invoke the fan, or terminate charging at some predetermined temperature(s) to keep the charger's electronics within a safe range. That your charger continues to operate and we don't hear increased OBC failures with age, suggests it's probably being adequately cooled.

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You have this correct. There is no issue with the system design nor does there need to be any additional cooling to the charger/inverter/motor. This is pointless and adds no benefit. There is a fundamental misunderstanding of the entire cooling system and how heat is distributed in the vehicle, this thread is going in circles and will likely continue to do so. I suggest some download the service manual and study the cooling design.

EVDRIVER said:

The topic here is charging heat not motor or inverter heat and they have nothing to do with the pack.

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Is it?

Either you or I haven't read/understood the OP thoroughly.

I understand the OP to mean that he was running the AC to cool down the charger. The charger has no water cooling in it, so what's the point in wanting the cooling fans running unless to cool the motor/inverter assembly. The heat transfer between the two is assured. And then the thermal soak caused by that hot unit is a hindrance to the battery pack cooling down.

If I have misunderstood the OP, then I don't see what the relevance of the discussion about running the AC was.

donald said:

EVDRIVER said:

The topic here is charging heat not motor or inverter heat and they have nothing to do with the pack.

Click to expand...

Is it?

Either you or I haven't read/understood the OP thoroughly.

I understand the OP to mean that he was running the AC to cool down the charger. The charger has no water cooling in it, so what's the point in wanting the cooling fans running unless to cool the motor/inverter assembly. The heat transfer between the two is assured. And then the thermal soak caused by that hot unit is a hindrance to the battery pack cooling down.

If I have misunderstood the OP, then I don't see what the relevance of the discussion about running the AC was.

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Yes the charger is fully water cooled, this a very basic feature of every production EV made.


Here is part of what he said which is incorrect:

"The big problem is that the battery stores a lot of heat energy - a sort of napkin-sketch example would be to say it probably has 1 kWh of energy stored as a heat differential between the environment and the battery temp at night. So even though it's 70F outside, the battery might only get down from 100F to 90F by the morning, then back to 100 where it's driven and cycled, rinse and repeat. Not so great for lithium chemistry.

I also found that the motor/controller under the hood has a *very* bad effect on this, caused by its cooling system behavior."


The motor and controller are not related to this issue and the charger is the only thing running when the car is stationary and since it is fully water cooled you don't need to run the AC.

donald said:

But surely for the cooling fans to cool the motor you'd have to have the liquid cooling system active, and that only operates when the car is in motion?

The fans run with AC because the condenser at the front has to be cooled else the AC won't work.

The only way to cool the motor/charger is to pass cold air over it. This is actually quite easy to do - set your heating on rather than your AC on (I assume your 2013 has a heat pump?). With AC, the radiator acts as a condenser and has to eject heat, whereas with the heating on the radiator acts as an evaporator and draws heat out of the air. You'd then be fanning colder air over the motor/charger.

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When the car is charging (while stationary), the coolant pumps run. You can hear them and feel coolant going thru the hoses connected to the PDM stack.

As for the OP's 2013 and having a heat pump. No, he has the S trim. It doesn't have the hybrid (w/heat pump) heater. I've looked under the hood of the S trim vs. my SV and can confirm that heat pump reversing valve isn't on the S.

cwerdna said:

donald said:

But surely for the cooling fans to cool the motor you'd have to have the liquid cooling system active, and that only operates when the car is in motion?

The fans run with AC because the condenser at the front has to be cooled else the AC won't work.

The only way to cool the motor/charger is to pass cold air over it. This is actually quite easy to do - set your heating on rather than your AC on (I assume your 2013 has a heat pump?). With AC, the radiator acts as a condenser and has to eject heat, whereas with the heating on the radiator acts as an evaporator and draws heat out of the air. You'd then be fanning colder air over the motor/charger.

Click to expand...

When the car is charging (while stationary), the coolant pumps run. You can hear them and feel coolant going thru the hoses connected to the PDM stack.

As for the OP's 2013 and having a heat pump. No, he has the S trim. It doesn't have the hybrid (w/heat pump) heater. I've looked under the hood of the S trim vs. my SV and can confirm that heat pump reversing valve isn't on the S.

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Correct on both points. The heater is the same as the 2011-12.

OK, let's squash some bogus misinformation here real, real fast before we get too far into page 2. Sorry, I was away all day on a *really* long-running work project today, and haven't been on a forum in quite a while so I hope I can keep on top of this.

Yes, the motor, controller (/inverter/charger, all combined as one "power management unit" as I'd call it) and battery are ALL thermally related. You can't connect two components with a big piece of conductive metal and say "they don't affect one another". You can't group them all under one huge insulating (yes, insulating, not conducting - the hood is NOT a good conductor of heat as I've observed by a cold hood and hot parts) cover and then say "they don't conduct". The motor/controller block heat DOES heat the battery pack if not dissipated by the cooling fan. This is observable by just walking out to any 2013 Leaf (S, in my case) at the end of a charging cycle and observing the temperatures. Very easy to test, very easy to see how they relate. The metal frame and shell of the car will either conduct heat away from the pack towards the cooler components, or will conduct heat from the hotter components into the battery pack. That's simple science. Let's move past the elementary stuff and think about how to solve the problem, not act like it doesn't exist.

Unfortunately, since most of this thread so far has been dominated by EVDRIVER sprawling bogus info about heat transfer, that's really all that's been touched on so far. Another good point is that the 6,000-plus watt charger does, in fact, produce a significant amount of waste heat that gets absorbed (via the activated water-cooling system) into the motor/controller block, which acts as a heat energy capacitor - the radiator does not do any cooling whatsoever without air moving through it - it's just another capacitor. Since there's an enormous amount of aluminum in the motor block components, with aluminum being the highest heat-capacity metal commonly available, most of that waste heat gets stored, not dissipated, at the time of charging. That stored waste heat gets conducted and dissipated through the car body over a much longer period of time than the charging cycle lasts, probably with the bulk of the waste heat getting flushed out the next time the car gets driven (which removes the heat extremely fast).

The issue here is that the cooling system was designed with car-in-motion in mind, not parked-car as in the case of charging - where most of the electronics heat is produced. This is why I see it as a "old school of thought" induced design flaw - Nissan's so used to making cars that have to cool while in motion, that they forgot things like creating an airflow feedback loop as found in the gap between the radiator and the fan shroud (check under your hood while the fans run - you'll find hot air sucking back into the fan!). Non-issue for ICE cars that don't usually produce much heat while stationary... but a big one for EVs where the opposite is true.

Oh - and it's worth noting: the water cooling system *is* active for the entire period of charging - you can tell by a slight hum from the controller block, and by squeezing a cooling line to feel the coolant flow (it's a brushless pump with a reservoir, no damage can occur by doing so). That's how the charger manages to dissipate the heat that would require a jet-engine of a fan to cool by air cooling. Unfortunately, though, there's no air cooling - there's just heat distribution; storing that waste heat in other system components instead.

ed.: ah, and yes, I've got the 2013 S, and was pretty disappointed to find that I didn't have the heat pump - after signing the lease. Can't comprehend why Nissan would develop two completely different heating systems for something as simple as saving a reversing valve on the S trim. But no - while I can probably use a heat pipe coupled to the exposed metal on the low-pressure hose and put the other end into the water-cooling loop :ugeek: , I can't reverse the A/C to blow cold air. I *SO* wish I could, though! :lol:

FalconFour said:

... the radiator does not do any cooling whatsoever without air moving through it - it's just another capacitor.

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That's just not true. It dissipates energy through radiant heat. There is also convection, even without forced air. Consider one of these: no fans…



It wouldn't make any sense for the coolant pump to run if the heat were never dissipated. There isn't enough thermal mass to serve solely as a "thermal capacitor" in the way you suggest.

Nubo said:

FalconFour said:

... the radiator does not do any cooling whatsoever without air moving through it - it's just another capacitor.

Click to expand...

That's just not true. It dissipates energy through radiant heat. There is also convection, even without forced air. Consider one of these: no fans…

Click to expand...

Lemme stop you right there... you see that radiator? It works because it's completely open-air and its surface is exposed to the air it's intended to heat. The Leaf, though, is completely insulated by its skin of thin metal sheets. Its radiator is inside those layers of metal and trapped hot air. Same way a toaster oven is designed to be "cool touch" - it keeps the heat inside by avoiding conduction. The inside will be blazing hot, but the outside... cool to the touch. Why? Air does not conduct heat very well - especially not stationary air. That's why the key here is to get that cooling fan to run while charging.

Eh, but this is worth tackling too. God... sorry if I seem like the disagreeable dick, but the info people keep posting here so "he-man master of the universe" authoritative-like, is just not accurate by the laws of science. :?

It wouldn't make any sense for the coolant pump to run if the heat were never dissipated. There isn't enough thermal mass to serve solely as a "thermal capacitor" in the way you suggest.

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Hence, why I edited my post with this link: http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html" onclick="window.open(this.href);return false;

Aluminum has a significantly higher specific heat than other common metals like iron or copper. Hence, yes, it actually is entirely possible that the motor/controller stores *ALL* the waste heat energy produced by charging - because it's distributed so evenly by the active water cooling system across the motor (windings, shell, magnet, etc) and the radiator, as well as anything else the cooling system is supposed to "cool". It's a heat distribution system, but a very poor cooling system while the car is parked.

It's the same concept that allows you to run a desktop PC for up to several minutes without a running fan (depending on the CPU type), but expanded to the hundred-pound heat sink scale. If that charger ran 24 hours straight at full capacity, still without activating the fan, it would absolutely melt itself.

OK, I can hear the crickets, and I know a dead-ended thread when I see it. :x Like I said, I don't intend to be and I'm sorry if I appear to be the disagreeable dick raining on everyone's parade. I really do think there's a problem that needs to be solved here, and hope to get some info on how to move forward with testing some fixes. Specifically - and I know this is another stubborn sticking point - getting that cooling fan to run on demand so as to be able to test its effect on pack cooling and power consumption. I know I kinda stabbed EVDRIVER in the eye earlier with a specific shout-out, but I don't want to make him(/her) nor anyone else feel squished out here.

I also hate writing posts that people see and go "tl;dr", but there's a lot to explain as to why I disagree Like I said, haven't spent time on forums in a while. Seems like in order to have a good point, it's got to have good information behind it.

Where from here, though? Well, I need to actually go pick up some larger sized freezer blocks to do more proper testing with, for starters. I used a bread-loaf pan packed as tightly as possible with ice cubes, then the bottom filled with water, last night. By the morning it was totally turned to cool water, and the pack was at 6 bars, 87/89/83F by Leaf Spy with an overnight low of 70. On the 3-mile drive home late-evening (all day in the 102-high sun with no ice, and only 3 miles driven) it was up to the mid-high 90s (can't recall specifics) and 7 bars again.

FalconFour said:

OK, I can hear the crickets, and I know a dead-ended thread when I see it. :x Like I said, I don't intend to be and I'm sorry if I appear to be the disagreeable dick raining on everyone's parade. I really do think there's a problem that needs to be solved here, and hope to get some info on how to move forward with testing some fixes.

Click to expand...

Not a problem. You do make some good points and have got me thinking about it more. At the moment I'd still point out that the front of the car is not completely closed off. I still think the radiator plays a central role but you do have me curious about how the convection would work. Some infrared camera work would be interesting.

But if your theories are right, you may not need to go through anything as complex as changing the fan setpoint. You could just raise the hood while charging, and then you definitely would have both sides of the radiator exposed to convection, as well as the other internal components you mention.

But, getting back to the battery; the battery case ends well behind the front passengers' feet. That's a long distance from the heat sources you're talking about. I'd think any trapped heat would conduct to outside air through the thin panels of the hood, etc, much more quickly than it could go several feet longitudinally through the floor pan to get to the battery case.

Good points, and I can see how it'd seem obviously unrelated. The way I see it, "heat rises" can only go so far, with my experience in PC cooling and other experiments. When the heat's as strong as I felt it just before posting this, it not only keeps the battery from cooling out to the environment, but it also most likely spreads to the battery considering the motor is much closer to the battery than the cool air outside - and the motor gets damn hot with the charger's heat (I mean, so hot I couldn't keep my hand on it for more than a couple seconds). At the very, very least, it's keeping the battery from cooling at its max potential. At worst, it heats the battery. I figure everyone can agree on that much

As for the hood, well... definitely not something I can do, with the hood I live in (my rent is lower than the Leaf payments, put it that way). What I might try, though, is somehow securing a fan outside and using that until I can figure out how to kick the car's own fan on while it charges (without using A/C and the ignition on). I could probably take some measurements and note the weather for the day, and how the pack temperature changes over each day. That'd give us some solid data to play with... maybe even present to Nissan to promote a firmware fix to run the fan more often. If, of course, the data proves that.

Without forced air moving through the radiator, though, raising the hood might just barely keep up with the charger's heat output, but not thanks to the radiator - instead likely because of the heat radiating off all the other highly-conductive aluminum parts under the hood that are attached to the cooling loop. (if the radiator was laid flat instead, with air traveling upward into open cool air like that radiator pic, we'd be telling a very different story!) If the fan was running, though (preferably in reverse, blowing out the front!), the cooling system would finally actually serve its purpose, and the radiator would *definitely* be cooling everything off. Rather quickly, too, as I've observed in cooling off all that "too-hot-to-touch" equipment in just 20 minutes of hood-open fan-blasting. Being made of so much aluminum definitely has the potential to be amazing, if it were used properly!

I can see your POV, FF, and glad I didn't misread your original.

Sorry I did not appreciate you didn't have the heat pump. Would be a good idea otherwise, though, eh?

It is a bit more complicated than a 'reversing' valve. It does not flow backwards, but instead there is a valve limiter which drops the pressure in the radiator, making it an evaporator, and there is a third matrix in the dash. The back pressure causes that third matrix to become the condenser and therefore heat is liberated from it. That's where the heating comes from.

Pretty clever, really. Renault's idea. It means you can run both heater and AC at the same time in winter and you'll actually be using the heat you are pulling out to put back into the car!

Anyhow, back to your situation - can't you simiply rewire the cooling fans at the front and arrange it so you power them independently? You could rig them to suck rather than blow - as you say, the mindset is thinking of flowing air during driving, which needs to be re-thought.

I still think hosing down the underside of the car and the tarmac it sits on can't hurt. it will pull heat from out of that area as the water evaporates.