AC Cutting Out

[negusm]

My AC will work great for a while and then just quit. It used to come back on after 15 minutes and work great again until it would stop again but now it seems like it works when the car is first started cold, then when it cuts out, it stays off permanently until the next day.

I checked the AC charge with a manifold and it's within spec for both high side and low side.

I swapped the AC relay with the Horn relay and no difference.

So, does anyone have any experience with these symptoms? Any idea which direction to go next? Compressor clutch? or AC Pressure Switch?

Do the pressure switches go bad? Normally, I'd just replace that but Mazda wants $120 for a new one. I don't buy Chinese parts.

Similar with the compressor (clutch). That's a whole lot more money for the whole compressor and I'll definitely troubleshoot it a bit more before replacing.

I just figure I'd ask for people's $.02c and maybe I'm also missing something easy.

2010 Mazda5 2.3L

 

[dlarkin_dc]

If it's high milage the AC belt would be my guess before the AC pressure switch. But the repeatability feels contradictory to just those parts as unreliable or bad, so maybe it's a hold out in the computer after too many fails.

Also the temp sensor down by the cabin filter, if that's disconnected the AC won't run, so it could also be a loose connection as the computer drops out the AC on a sensor loss.

If you can track one down, the service manuals have diagnostic step by step to figure out stuff like this. Better than throwing in parts in the dark. In the '07 manual thers 10 causes for "No cool air" and most are comms and wiring, not parts. I've attached a copy of that section.

 

[negusm]

Thanks for the info. I do have the service manual and will crack it open.

I don't think the temp sensor is the issue. Cranking the temp down to 60F makes the fan come on full blast, no problem. The fan also ramps up and down as I get closer or or farther away. I assume that if the temp sensor was bad, it wouldn't make the fan work like that? Worth a consideration, regardless. I won't discount it.

I have a feeling that the ECU isn't calling for air so it's a sensor somewhere. I do plan on breaking out my Power Probe and testing the AC relay and Compressor Clutch circuit. If those work while the AC is refusing to work, I'll focus elsewhere.

 

[r1080]

Does your car have an outside temperature sensor? Is it accurate? My AC was acting up when my outside temperature sensor went bad. Would not allow AC to get cold with an outside temperature reading of 2X to 3X degrees even though it was in the 80s.

 

[Silentnoise713]

Try clearing the AC drain hose? When clogged, it causes moisture build up which can lead to the evaporator coil freezing up. Once thawed, it works again.

Double twist piece of steel wire with a drill, and fish it UP the drain tube.

 

[negusm]

Some more good suggestions.

It's not a freezing evap coil or the AC would come back on after a bit. Like I said, you get one good run on a cold startup and then when it cuts out, it never comes back. Even with running around and doing multiple stops for some errands for an hour.

 

[Silentnoise713]

Some more good suggestions.

It's not a freezing evap coil or the AC would come back on after a bit. Like I said, you get one good run on a cold startup and then when it cuts out, it never comes back. Even with running around and doing multiple stops for some errands for an hour.

I thought it does come back so whatever it is, it is temporary. This happened to my '08 about 2-3 years back, It took more than a few hours for it to return to normal. I too thought I had some HVAC component failure but after clearing the drain hose, AC has been solid.

When you click AC on/off, do you hear the clutch engage/disengage?

 

[negusm]

It comes back after the car sits overnight.

Months ago it would come back after about 30 minutes. At that time a frozen evap crossed my mind but since it's gotten far worse, I discounted it.

I'll check the drain. It's easy and free after all.

 

[Silentnoise713]

Months ago it would come back after about 30 minutes. At that time a frozen evap crossed my mind but since it's gotten far worse,

Yep, same pattern. I hope it is as simple as that for you. Make sure you really stick it up high, and you'll know b/c a gush of water/crude will fall out/on you.