So....our new car (only 151,000 miles) has an A/C that works great......sometimes. For no apparent reason, the compressor kicks out and you only get ambient air. Then, for no apparent reason, it works again.

Really tired of this gremlin. The compressor is relatively new, plenty of Freon. No real reason it seems to quit or that it heals itself. A couple of times, I killed the climate control. Killed the engine. Waited 30 seconds or so. Restarted engine. Restarted climate control. Worked like a charm for anywhere from 10 minutes to an hour. Today, however, no luck with this particular superstition.

This model has a common problem, that the relay that runs the A/C compressor clutch was made of tinfoil and chewing gum. It's been updated with a new, heavier duty part number. Doesn't matter. Swap relays, no change. Or sometimes it works. Or sometimes it works after 20 minutes or so.

I did notice that today when I pulled the relay, one of the posts was really, really hot. And this was after the A/C had been inop for 15 minutes or so.

I've seen wrecking yard climate control heads online for $40 or so. Been tempted to try one on the off chance that the climate control brain was wacky.

Any suggestions welcomed. As stated above, 2008 Acura MDX.

When it kicks off, do you have a full 12 volts at the plug that energizes the clutch?

Do you have a blend door problem?

My limited experience with blend doors (06 Chevy pickup) is that it goes from cold ac straight to hot air, although the hot air could have been ambient temperature since it was a 100 plus degree day. Shutting off the ac or restarting the pickup would fix it for a minute or 10 or an hour or so.

The compressor shuts off, so not blend door.

CanyonAg77 said:

---

The compressor shuts off, so not blend door.

---

Gotcha, so it has to be between the control unit and compressor. Could you have a low or high pressure switch giving you problems?

Possibility. The random failure mode makes me think it's not that simple.

Compressor clutch gap.

Remove clutch, remove "shim" (aka washer) and reinstall clutch.

Pretty new compressor. Still think that's it?

CanyonAg77 said:

---

Pretty new compressor. Still think that's it?

---

Common issue on aged ones, but still worth checking for sure.

So I looked at the A/C clutch. Factory compressor clutch gap specs are 0.32mm to 0.65mm. The biggest feeler gauge I had was 0.645mm, and it went in easily.

Took it apart, it had a 1mm shim. Tried it with no shim, clearance went to 0.00. Tried to find a smaller shim, no joy. Decided to file my 1mm shim down and see if that helped. As I rubbed it up and down the file, it suddenly popped apart, revealing that I actually had two 0.5mm shims.

So I put just one 0.5mm shim back in. This brought the gap down to 0.25mm. But I left it alone.

At the same time, I looked at the ground cable, because I had been having some electrical gremlins. For instance, the radio would keep the XM radio stations, but lose the AM and FM stations. I was surprised at how tiny the cable was, and how the only connection was a tiny bolt, bolted to a painted surface on the body. So I cleaned the battery and body end of the cables, and also sanded the connection on the body down to bare metal.

Have only been driving it a limited amount the last few days, but everything is working so far......

Update: Gremlin kept coming back, but never while mechanic could see it. A few weeks ago, we're coming in from NM, compressor stops. So we unload at the house, leave the car running, take it to the mechanic. He checks fuses, relays, etc, all good. Puts car on a lift, touches the wire going to the compressor.....compressor kicks in.

Apparently, the plug at the compressor was bad. Fixed that, has been working since. Aaarggh.

the most basic fixes are always the most aggravating

sts7049 said:

---

the most basic fixes are always the most aggravating

---

The inconsistency is what drive me bonkers. If the plug had just broken, I would have been much happier

CanyonAg77 said:

---

sts7049 said:

---

the most basic fixes are always the most aggravating

---

The inconsistency is what drive me bonkers. If the plug had just broken, I would have been much happier

---

I had the same issue when I had the 99 F250 V10.

Truck ran great but would every now and then stumble with no hard codes.

I changed plugs, coils, air filters, fuel filters, tried cleaned injectors, mass air flow sensor, throttle body etc.

Finally gave up and let AgMechanic take it to his job and after two days he figured out the #7 fuel injector plug was wonky. Touch it, and it would smooth right out. A new pigtail and it was good again.