94 Corolla AC Issue Please Help

[decravens]

My 94 Corolla AC won't turn on. It did this before when it was low on coolant, but this time it has enough coolant. Can anyone tell me which temperature sensors are in the AC circuit and the location under the hood? No leaks, AC clutch checks good, but the light on the dash won't turn on. Fan blows fine. Any help would be appreciated, summer is kicking up in SC and I don't want to be without working AC!

[ShawnM]

There are low pressue switches that will prevent the compressor from turning on if the system is low. When you say "coolant" are you talking about the green engine coolant or are you talking about the freon in the A/C system? The engine coolant dosent really have anything to do with the A/C system.

[decravens]

My father in law phrased the question as above asserting I didn't know what to ask. The real problem is that the clutch on the AC won't engage unless shorted directly to the positive terminal on the battery. Refridgerant's fine, the high pres and low pres going into the firewall are warm to the touch, which caused me to follow it back to the relays and fuseable links to see if the system was turning on at all, which all tested fine with a multimeter. The reason I ask about the water temperature sensor is because on the schematic, it's smack dab where the symptom occurs, and I also noticed that the temperature gauge on the car basically just works whenever it feels like it. I really am all but banging my head on the wall on this one, since I can't really afford to have it looked at by a specialist for the time being.

[Rip The E Brake]

That AC switch DOES go bad sometimes...

[Suprawillis]

Okay so there are a few things you can do.

First, check the compressor wire and make sure it has not disconnected itself. It is very deceiving, and it is just a single wire that can easily be overlooked. Look under the alternator, and you should find the wire attached to a small clip going into the compressor. I just noticed this last week and now my AC is back to normal, which brings me to my next suggestion.

If you jack up te passenger side, and undo the plastic splash guards(they are held on with a few 10mm bolts). You will have access to the AC compressor pulley.

There is one 10mm bolt holding it on the clutch to the pulley. When the AC is off, the clutch is stationary, and does not move with the pulley. Now turn on the AC, and if the clutch spins, this will tell you that compressor is working, and that the clutch still has good engagement. If it does not spin, then this tells you that the clutch is worn out.

It is a fairly simple fix. If you have to remove the clutch, you will need one of those oil filter removal tools and fit it over the pulley. This will keep it from spinning while you loosen the 10mm bolt.

When it is loose, take the bolt out and the clutch should come out. Now this is where you need to pay attention. When you remove the pulley, a shim will fall out. This shim fit around the bolt when inside the pulley, acting as a spacer because the when the AC is activated, the compressor becomes internally magnetic pulling the clutch in, so that is mates with the compressor and spins.

If you have more than one shim, remove one, keep the other installed, and turn on the AC and see if the compressor "grabs" or pulls the clutch in enough to spin it.

Now of course, if you don't care, you can remove the shims altogether and when you re-install that 10mm bolt that holds the clutch to the compressor, you will have 24/7 AC. That shim is designed to give the clutch just enough space to back off the compressor when the AC is not working. Then when it gets cold, add the shim and you have no more AC.

Going back to step one, if the clutch engages like it should when you press the button, and you still don't have cold AC, then you could be low on freon, and have a leak. OR, the valve inside the AC exchanger could be bad. THAT is another installation how-to. But it's not kick ass hard.

Make sure your belts are in tact. And if you do get freon, get the kind that has the leak detector/UV ink as well as a pressure gauge.

[Rip The E Brake]

Try replacing the AC switch on the dash... they do go bad, before you drive yourself nuts.