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Heating and AC out

Posted: Sun Apr 18, 2021 11:34 am
by davidr
I bought a used 2011 leaf a couple years ago, and everything was operational at that time. Then one day I discovered the AC wasn't working anymore, and doing some testing also discovered the heating wasn't working anymore.

I took it to a dealer, and they claimed something had shorted and blew a fuse in the dc-dc converter, and they'd need to replace the heater, compressor, and dc-dc converter.

After doing some digging, it seems like the heater and AC are on separate fuses, so it seems odd that one short would impact both. Anyone have any ideas/insights?

The DTC codes that are coming up are:
>B2788 0009 HVAC Comp Over Current HAC-99
>B2770 0009 HVAC PTC Heater Circuit HAC-75

Re: Heating and AC out

Posted: Sun Apr 18, 2021 12:53 pm
by knightmb
davidr wrote:
Sun Apr 18, 2021 11:34 am
I bought a used 2011 leaf a couple years ago, and everything was operational at that time. Then one day I discovered the AC wasn't working anymore, and doing some testing also discovered the heating wasn't working anymore.

I took it to a dealer, and they claimed something had shorted and blew a fuse in the dc-dc converter, and they'd need to replace the heater, compressor, and dc-dc converter.

After doing some digging, it seems like the heater and AC are on separate fuses, so it seems odd that one short would impact both. Anyone have any ideas/insights?

The DTC codes that are coming up are:
>B2788 0009 HVAC Comp Over Current HAC-99
>B2770 0009 HVAC PTC Heater Circuit HAC-75
Replacing the dc-dc converter is a red flag, if that wasn't working, then none of the 12 volt system stuff would work like the lights, steering, brakes, etc. Unless there is "another" dc-dc converter for the AC/Heating system, maybe someone more technical can chime in...

Re: Heating and AC out

Posted: Sun Apr 18, 2021 3:40 pm
by GerryAZ
David,

Did you try running the A/C after clearing the DTC's? As Knightmb said, the DC-DC converter is OK or the car would not keep the 12V systems running. There is a high-voltage junction box with fuses in it for the various high-voltage circuits (DC-DC converter, heater, A/C compressor) and a blown fuse could be the issue for the heater but the A/C compressor is probably being kept from running by the controls seeing the overcurrent error. Do not replace the high-voltage junction box without fixing whatever caused the fuse(s) to blow, otherwise you will just blow more fuses. Nissan does not offer replacement fuses, but a competent technician might be able to open the junction box, determine fuse needs, obtain fuses from an electrical supply company, and replace the blown fuses. It should be noted that failure of the electric heating elements in the little hot coolant tank could create a short circuit and blow the fuses that supply that circuit, but should not impact the A/C compressor.