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HVAC (A/C) cuts out

Posted: Sat Jul 21, 2018 12:56 pm
by Marktm
Stored DTCs - B2785 B2786 B2791 HVAC. A/C cuts out for several minutes. This has happened a number of times - usually for 2-5 minutes, then A/C slowly cools down again. This happened yesterday on the freeway. Outside temps were almost 100 oF - got a little uncomfortable before cooling started again.

Any such experience/remedies?

Re: HVAC (A/C) cuts out

Posted: Sat Jul 21, 2018 3:52 pm
by Nubo
Marktm wrote:Stored DTCs - B2785 B2786 B2791 HVAC. A/C cuts out for several minutes. This has happened a number of times - usually for 2-5 minutes, then A/C slowly cools down again. This happened yesterday on the freeway. Outside temps were almost 100 oF - got a little uncomfortable before cooling started again.

Any such experience/remedies?
The first two codes are for over-heat with possible causes being the compressor itself, cooling fan, or low refrigerant and/or leak

Oddly enough the third code is for "low speed high load" which has one of the possible causes as "refrigerant overfill". But perhaps that's happening upon restart.

If this happened on the freeway at cruise speed, I'd think that'd rule out the cooling fan. If it was stop-and go the cooling fan would be a suspect. I'd definitely check the refrigerant pressure. Does your AC seem a bit weak even when it's running?

Re: HVAC (A/C) cuts out

Posted: Sun Jul 22, 2018 2:23 am
by lkkms2
When I had my 2011 SL Leaf I didn’t drive in 100F temperature, but I seem to remember the AC working better when driving in D vs ECO.

Re: HVAC (A/C) cuts out

Posted: Sun Jul 22, 2018 3:38 am
by LeftieBiker
Is the condenser clogged with bugs or other detritus?

Re: HVAC (A/C) cuts out

Posted: Sun Jul 22, 2018 6:24 am
by Marktm
First - appreciate the good comments:

- When this happened we actually were slowing and near stopping on the freeway
- Similar situation as best I recall was while quite hot (not 95+, but hot) and in stop and go traffic
- I've never had the A/C checked for proper refrigerant load, and it is factory original charge (no records of any maintenance required when I bought the car)
- There is some noise (minor) from the equipment hood that appears to be coming from the compressor (with HVAC on). Both fans run and appear to be quiet and unrestricted.
- Possible that this is a common problem with extremely hot weather (design issue)? I watch the climate control power screen and know that when this happens, the kW drops to zero. What is strange is that the power level (on A/C only) will often climb to over 2 kW - almost like the
heater circuit is on even though the set temperature is well below ambient and cabin temps. I guess I need to make the mods to cut the
heater circuit out completely during hot months.
- The A/C does a great job of quickly cooling the car with plenty of cold air.
- bottom line? have the refrigerant level checked??

Re: HVAC (A/C) cuts out

Posted: Sun Jul 22, 2018 8:01 am
by GerryAZ
The HVAC controller will turn off the compressor if evaporator temperature gets close to freezing (32 F or 0 C) so check to make sure cabin air filter is not restricting air flow and run blower fan at moderate to high speeds for maximum cooling. Your description of cooling loss for 3-5 minutes is consistent with evaporator freeze protection. Condenser fans should move a lot of air and make some noise so check air flow since the error codes indicate overheating and the controller will shutdown the compressor to protect it (this would also yield the symptoms you have). I installed a temporary resistor to keep the heater from turning on in my 2011 and could still see at least 3 kW compressor draw under high ambient conditions so your 2 kW load is reasonable. The heater on while using A/C happens at moderate temperatures so it probably was not involved in your loss of cooling condition (although I highly recommend the modification and would have purchased the plug-and-play kit if my 2011 had not been totaled).

The A/C systems in both 2011 and 2015 work great in high ambient temperatures so your symptoms are not normal.

Re: HVAC (A/C) cuts out

Posted: Sun Jul 22, 2018 10:51 am
by Marktm
GerryAZ wrote:The HVAC controller will turn off the compressor if evaporator temperature gets close to freezing (32 F or 0 C) so check to make sure cabin air filter is not restricting air flow and run blower fan at moderate to high speeds for maximum cooling. Your description of cooling loss for 3-5 minutes is consistent with evaporator freeze protection. Condenser fans should move a lot of air and make some noise so check air flow since the error codes indicate overheating and the controller will shutdown the compressor to protect it (this would also yield the symptoms you have). I installed a temporary resistor to keep the heater from turning on in my 2011 and could still see at least 3 kW compressor draw under high ambient conditions so your 2 kW load is reasonable. The heater on while using A/C happens at moderate temperatures so it probably was not involved in your loss of cooling condition (although I highly recommend the modification and would have purchased the plug-and-play kit if my 2011 had not been totaled).

The A/C systems in both 2011 and 2015 work great in high ambient temperatures so your symptoms are not normal.
Ordered a new filter - appears easy to replace
Both fans operate quietly and pull lots of air
The compressor is little noisy, in fact I thought it was the inverter humming until checking more closely (due to this issue)
Good to know that the A/C unit itself will pull up to 3 kW. Don't know that I've seen that high, but when on full blow/cool, it still cools the cabin down quickly
Going to finally order the kit - just makes sense in Houston as the heated seats/steering wheel work 99% of the time

Thanks for the info.

Re: HVAC (A/C) cuts out

Posted: Tue Jul 24, 2018 4:46 am
by metzroth
I have a 2011 leaf and just started playing with LeafSpy in the last 30 days. I have the same 3 codes - B2785, B2786, and B2791. I've been debating what to do about it, since the car still cools itself well. I've noticed it cut off from time to time, but nothing that would be alarming or cause me to take it to a shop. I already cleared the codes 5 days ago and changed the filter. The codes re-appeared, so I have to assume the filter was not the problem. My next thought is to check the refrigerant level. If anyone has a link to a refrigerant checking tutorial, please link it :-). I hate to go pay nissan to diagnose this when it's not a "real" problem yet. IE wife isn't complaining yet.

Re: HVAC (A/C) cuts out

Posted: Tue Jul 24, 2018 6:21 am
by Marktm
The 2012 manuals are available free on-line. The two that are needed for HVAC diagnostics/repair are:
HA.pdf
HAC.pdf
It's likely they will work for your 2011 also and have very complete documentation.

Re: HVAC (A/C) cuts out

Posted: Tue Jul 24, 2018 6:50 am
by SalisburySam
GerryAZ wrote:The A/C systems in both 2011 and 2015 work great in high ambient temperatures so your symptoms are not normal.
Ditto for 2012! My black SL chills down very quickly in the hot sun. You should experience the same indeed.