Hey all - our 2012 Quest has 146k miles. All maintenance up to date. Last September our AC went out and a local, highly reviewed shop replaced the compressor for about $1500. He said he looked up the company that manufactures compressors for Nissan and bought it directly from them rather than paying the higher price from Nissan directly (can’t remember the name). 6 months later the AC began cutting out when driving very slow (like traffic jam slow) or idling. The same shop was able to reproduce this at idle and confirmed it was the compressor cutting out, and not the fan (their first guess). They replaced the compressor. A month or so later and the new compressor is doing the same thing. Does anyone have experience with this? Do I need to bite the bullet and take it to the dealer for diagnosis and repair?

When you say "cutting out" do you mean the compressor clutch disengages and the compressor no longer functions?

OR, do you mean you simply get warmer air when idling or in stop-and-go conditions?

If the former, there could be an intermittently-malfunctioning relay, bad ground, or other electrical issue causing it to stop. An incorrect refrigerant charge can also cause this.

If the latter, it's an airflow issue. I'd clean the condenser thoroughly, clean radiator fins, and verify that electric fans are functioning properly (one should be on when it's at operating temp, another should kick on with the AC).

Also, verify that they replaced the receiver/drier when new compressor went in. Otherwise, the same contaminants that killed the first compressor would kill all subsequent replacements.

The mechanic said that the compressor itself was quitting, but only while idling or driving very slowly. I wish I knew more about the components, but I know they did change other peripheral stuff all as part of the compressor replacement. Charge was definitely good. Would there be a particular relay I could try replacing? And is the condenser cleaning something I can do? I mean I guess I can take it back to these guys - they didn’t charge me for the second replacement, it just seems they may not really know what they’re doing.

A compressor shouldn't shut off intermittently, and it's certainly not dependent on vehicle speed. It's got an electrically-actuated clutch. It's either on or off, controlled by the switch on the dash.

Condenser cleaning is a simple process. There's a handy wand you can get that goes on a garden hose, just be sure to wash from the inside out (pushing any debris / dirt / leaves out towards the grille.

You're armed with a little more info now - Let us know what they say.

Will do - thank you very much for the fast info!

Welcome aboard!

Could be your high/low pressure switch for the gas. Alot of times compressors shut off when it detects no gas to protect the compressor.
Id say you have a slow leak somewhere and your gas pressure is low at idle and it switches off because its not detecting enough pressure due to low gas.

Follow that avenue too

drgtr wrote: ↑

Sun Oct 04, 2020 11:09 pm

Could be your high/low pressure switch for the gas. Alot of times compressors shut off when it detects no gas to protect the compressor.
Id say you have a slow leak somewhere and your gas pressure is low at idle and it switches off because its not detecting enough pressure due to low gas.

Follow that avenue too

Is that switch something that I can replace myself? I’m going to try the condenser cleaning today. I’m doubting a leak just because they’ve checked it multiple times (including after the symptom had been around for a couple months) and they said the charge and the high and low pressures were all fine every time.

Update: Taking it back in on Monday. He said it doesn’t have an orifice tube but instead an expansion valve and that it was replaced, along with the drier and associated O-rings, when the compressor was replaced. But he made it sound like they had not thought to check the pressure switch so they are going to look at that and any relays associated with the compressor. If that doesn’t work.... my money goes to the dealer I guess...

Update 2: The same shop fully tested it again and concluded it was the compressor. So put another aftermarket compressor in, including peripheral components, tested the expansion valve and the pressure switch, and fully flushed the system. Two days in and so far so good - but it’s a lot cooler out this weekend so maybe when it gets back up in the 80s next week I’ll know for sure. It did still appear to be cooling well at idle, which was the original problem.