Part Number of Heater Fluid Temperature Sensor on 2012 Leaf

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andyc

Member
Joined
Sep 14, 2019
Messages
7
Location
UK
Does anyone know the Nissan part number of the Heater Fluid Temperature Sensor? (Note this isn't the Coolant Temperature Sensor, which is Nissan part number 22630-3NA0A.)

I have a 2012 Leaf with the fluid based heating system - it's the one with the PTC Heater having one of these part numbers B7143-00Q0A, B7143-00Q0D, B7143-00Q0F, B7143-00Q0H, B7A43-00Q0K.

When I bought the car in the summer the weather was warm and I didn't test the heating. The heating blower and AC all seem to work fine, but it doesn't heat up. Symptoms are as per this post: https://www.mynissanleaf.com/viewtopic.php?t=23142

Hoping it might not be the PTC Heater... I've not got to that yet, but have so far measured the resistance of the Heater Fluid Temperature Sensor and it appears to be too low (it's 254 ohm at an ambient temperature of about 15 degC). With ref to page 14 of the HAC manual downloaded from here: https://ownersmanuals2.com/nissan/leaf-2012-repair-manual-heater-air-conditioning-control-system-section-hac-43047 a resistance of 254 ohm corresponds to a water temperature of 60 degC, which would mean the control system thinks the fluid is already hot. Does anyone know the maximum temperature the fluid can reach? The Resistance v Temp spec graph goes up to 80 degC, so perhaps that's the max? At 15 degC the spec graph shows the sensor resistance should be about 1.3 kohm so I'm suspecting (and hoping) it's just the sensor that's faulty.
 
You sure someone didn't install an aftermarket switch in the dash? It's a common modification to shut off the heat in moderate climates when you just want defrost. That would cause the symptoms you're dealing with... Look for extra harnesses underneath the radio (you'll have to pull the plastic in front of the radio)

https://www.mynissanleaf.com/viewtopic.php?f=37&t=11412

Some people just hacked a resistor in:
https://www.mynissanleaf.com/viewtopic.php?f=37&t=11412&start=140#p501880
 
Many thanks Lothsahn, but I can't find any mods that might prevent the heating coming on. Before posting I've been reading extensively on this forum and it's a fantastic resource (thanks all!). I've seen both those links and checked for all those mods already, but they aren't present.

My problem is finding any part number for the heater temp sensor as a starting point. My car is an import and the parts system at the Nissan UK dealer won't identify the correct part. One option is to pay Nissan's expensive price for a part for a similar age UK car, but rather than do that I'm hoping to source a part on Ebay etc.
 
andyc said:
Many thanks Lothsahn, but I can't find any mods that might prevent the heating coming on. Before posting I've been reading extensively on this forum and it's a fantastic resource (thanks all!). I've seen both those links and checked for all those mods already, but they aren't present.

My problem is finding any part number for the heater temp sensor as a starting point. My car is an import and the parts system at the Nissan UK dealer won't identify the correct part. One option is to pay Nissan's expensive price for a part for a similar age UK car, but rather than do that I'm hoping to source a part on Ebay etc.

Understood. Wanted to make sure you'd checked the easy stuff first. Do you have a copy of the service manual? I'll check my copy and see if I can get you a part number tonight.
 
Thanks again Lothsahn, I have this service manual: https://ownersmanuals2.com/make/nissan/leaf-2012-372

A part number would be very much appreciated.
 
The service manual doesn't list the part. The replacement procedure is quite easy: HAC-152.

You could try calling a dealership in the US to get the part number and cost. Maybe they could even mail it to you? Alternatively, I know someone who has a few wrecked Leafs. He may be willing to pull the part for you, but I don't know if any of them are good--they were all flooded.

I've asked him to post on this thread if he's got one. I've not heard of this part going bad, so it's not a common failure, and the Leaf is an uncommon car, so you may have difficulty finding it on ebay.
 
I haven't found a definitive answer, but it's *possible* that the sensor is part of 924013NA0A "hose assembly". This is just going by diagrams that seem to show the sensor attached to the hose, without a separate callout for the sensor. More likely it's just a hose, but maybe worth a call.

Callout 27185 in the diagram:

040_ZE0_0000000054.jpg
 
My friend emailed me back. Hopefully he'll post soon. He thinks his sensor is fine--he asked for the voltage ranges, so I suspect he's going to test it to verify.

He could likely send you the whole hose with it attached, if you ask. Might make it easier to swap and such too.
 
Many thanks Nubo, the exploded view system diagram on page 68 of the HAC manual shows the sensor definitely attaches to that section of pipe. Interesting idea that the sensor might be included as part of 924013NA0A "hose assembly". A quick google hasn't answered that, but it's given me something to move forward with.
 
Many thanks again Lothsahn, having a spare available would be great.

Things have moved on a bit since yesterday. It occurred to me that the trick of keeping the heater off by disconnecting the sensor cable and installing a low value resistor could potentially be adapted as a test to get the heater started. I therefore disconnected the sensor cable and installed a 1k ohm resistor. With the heating temp set to the 30 degC max the heating stayed cold and the energy meter only showed very slight draw over 26 degC setting as one of the other ancilliaries came on.

I'll park the heat sensor investigation for now, with my 1k ohm resistor option as an extra test still available and move on to look for the main cause.

Hoping it won't be the PTC Elements Heater, but expecting the worst. Before this will try investigating the A/C auto amp (A/C control) function, as it's easier to get to.
 
andyc said:
Many thanks again Lothsahn, having a spare available would be great.

Things have moved on a bit since yesterday. It occurred to me that the trick of keeping the heater off by disconnecting the sensor cable and installing a low value resistor could potentially be adapted as a test to get the heater started. I therefore disconnected the sensor cable and installed a 1k ohm resistor. With the heating temp set to the 30 degC max the heating stayed cold and the energy meter only showed very slight draw over 26 degC setting as one of the other ancilliaries came on.

I'll park the heat sensor investigation for now, with my 1k ohm resistor option as an extra test still available and move on to look for the main cause.

Hoping it won't be the PTC Elements Heater, but expecting the worst. Before this will try investigating the A/C auto amp (A/C control) function, as it's easier to get to.

Good to hear you've made progress on the troubleshooting. There's a fuse inside the PTC heater that commonly goes bad. I've seen numerous posts on the forum about this. If I had to bet, I'd say that's what's gone wrong in your heater unit.

The annoying part is fixing it involves removing the heater, which involves draining and refilling the coolant as well as removing lots of things in the way. The good news is replacing the fuse is inexpensive...
 
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