2005 Toyota Matrix with 209k miles, The A/C just recently started working randomly.
My local mechanic, like Scotty, suggested I check the relay before coming in to see him. Relay was good but I replaced it just in case. My mechanic said to swing by and he would check the pressure, pressure is good, looks like no leaks.
A/C Clutch is not turning when A/C is on, except randomly. My mechanic asked me to check the plug going into the compressor and see if it is getting power. I tried to check it, but I think it is only providing power when the car is on, and with the belt running it is not very easy or safe to check the plug. I would think it is getting power, as it randomly works.
Any ideas of anything else I can check before getting a new compressor?
Thanks a bunch!
Any ideas of anything else I can check before getting a new compressor?
Everything else. Why start by replacing the most expensive part of the system?
What are your system pressures? Is there enough static pressure to reliably prevent the low-pressure cutout from disabling the compressor?
Thanks for the assistance @chucktobias
My mechanic said it could be the clutch not engaging, but he wanted me to check some other things to make sure that is it, he didn't want me spending the money unless I had to. I don't know what the pressures were, but he said it was completely charged.
When it randomly decides to work for a bit, the air is quite cold fwiw.
If the static pressure is too low, would it allow it to come on for a bit and then stop?
Should I force activate the relay with a paper clip for a moment to see if the clutch engages? The thought being, if it won't start the clutch, the clutch is screwed up?
Thanks again!
If the static pressure is too low, would it allow it to come on for a bit and then stop?
If the refrigerant charge is inadequate the low side will go into suction and can trip the low pressure cutoff. Or the low pressure switch might have an intermittent fault (the car is 18 years old after all). The point is there is a lot to check on before condemning the compressor. The low pressure cutoff is just one example.
Thanks, I will do a check on the pressure switches!
I have run a few tests, here is what I have found. I checked the High pressure switch, and each time I check it, it is in the closed position. The low pressure switch is behind the dash I think. I tested to see if the clutch coil is possibly bad, and the ohms did read good at 4.2
I started the car and watched the clutch and fan. The clutch engaged at first for 30-45 seconds, and the fan was on, when the clutch stopped the fan did too. The fan would then re-engage for several seconds before the clutch, and clutch came back on, but for more like 10-15 seconds and quit, and the fan followed.
I noticed though that after a couple of 10 second cycles, the fan started, and I expected the clutch to start after a few seconds, it did not. The car was still cold, being on for maybe 2 minutes, and the fan was going but the clutch had stopped.
I let it run for a few minutes, the fan never stopped, and the clutch did not start again.
Would that indicate anything, or am I just being hopeful?
Thanks!
What are the system pressures doing while all this is happening?
I was doing this at home, so not sure on that. If the pressure was low, wouldn't the pressure switch open and cut power to the compressor, and also trigger the fan to shut off?
It depends on how low. The fast cycling you describe is typical if the low side goes into suction when the compressor engages. A manifold gauge set is the minimum requirement for AC diagnosis. That's for checking mechanical operation of the system. If it turns out you have a problem in the electronics you would need a bidirectional scan tool for diagnosis.
So I went outside to try something. Car was cold, started it up and the clutch engaged for 30 seconds or so, then started cycling 8 seconds clutch engaged, 8 seconds, off. When it turned off, the fan also quit. It took longer this time, maybe 10 minutes of the 8 second cycling at 60 degrees outside, and then clutch went out and the fan stayed on. When that happened, I turned the a/c button off and the fan shut down. Turned the A/C back on, and the fan comes on but no Clutch.
I looked it up online, and it seems that short cycling while idling at not hot temperatures can be normal. I fired up my GX470 to test the theory, and sure enough it was cycling at about 9 or 10 seconds.
I admit that I have never messed much with air conditioners until now, never had one acting up except my GX470 that needed a recharge a few years ago.
So if the fan is running when the clutch completely stops, does that not indicate that the pressure switches are reading correct pressure because the system is turning the fan on while it thinks the clutch is engaged?
Thank you again for all the help!
You're really working blind here. What's normal is going to depend on the vehicle and it should be documented in its shop manual, possibly the owner's manual. Maybe Scotty would know off the top of his head (he has a Matrix after all) but I don't know the specifics for your car.