Do I need to replace the A/C Clutch, A/C Relay, or A/C Belt?

Question

My '05 Mazda Tribute (just over 200,000 miles) is having problems with the A/C. A while back it was the freon according to the previous owner. I connected a pressure gauge to the low pressure end of the A/C tubes, and the pressure wasn't dropping once I turned the car on (my understanding is that it drops as the clutch engages - if that is wrong, please correct me). So I checked the clutch to see if it's spinning, and it is not. From there I check the fuse, and it is still good. After that I check the relay, and it appears to be good. When I later turned the car off and turned it back on, the A/C clutch was intermittently spinning for a few minutes and then stopped spinning all together.

Here are the three questions:

1. Can the power supplied through the relay go in and out(causing the clutch to start and stop spinning)?
2. Does the fact that the clutch is only spinning part of the time mean that I should replace the belt? And if so, any special requirements other than releasing the tension on the belt, remove old one and repeat for installing the new one?
3. Does the fact that the clutch is only spinngin part of the time mean that I should replace the clutch? And if so, how do I do that?

Answer 1

I'm not sure there is anything physically wrong with your clutch or belt. The clutch is designed to be turned on and off as needed. You can test the clutch by locating the relay located in the engine side fuse panel, then jump the power to the clutch pin. You have to pull the relay to do this. If you can manually engage the clutch by doing this, you can prove whether the clutch is working correctly. Usually, the bearings will be the first thing to go out on the clutch.

If the clutch proves out to be good, the next thing you can check is to see if the relay itself is bad. Change this out with another relay in the same fuse panel as they are standard. As long as they are the same shape, they should be exactly the same. You can also apply power to the subject (12v) relay while checking continuity. You can use this diagram to see how the relay lines up (if not exactly the same, it should look something like this):

While you are in the fuse panel, you might also check to see if the fuse is good there (assuming there is one).

There is also a pressure sensor, which, when the pressure gets low (I believe), it tells the A/C compressor to kick on. I'm not positive on how you can test this, though. If it isn't working correctly, it won't be telling the computer that your A/C compressor clutch needs to activate.

If all of this looks good, I think your problem lies in the amount of refrigerant in your system. You can get refrigerant from your local auto parts store or Walmart, some of which comes with a gauge. This will allow you to recharge the system if needed. It also gives you instructions on exactly how to do it.