Does your air conditioning work intermittently? I had this issue in a Toyota Corolla. This is the procedure I took to fix the problem.

How to Repair Intermittent Air-Conditioning

The air conditioning in the Corolla started to be intermittent. One day it just stopped working altogether. The ac compressor would not engage. I recharge the system with fresh r134a, but it still would not come on. I decided to check the compressor relay, by swapping the relay between the ac compressor and the horn, since they are very similar.

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How to Fix an AC Compressor Relay:

  1. Open the hood.
  2. Locate the fuse box, it is near the battery, and push the tabs on the sides to open it.
  3. Find the AC relay. (Refer to the diagram on the inside cover of the fuse box.)
  4. Then find the horn relay.
  5. Pull both of them out and swap them.
  6. Test the AC. If it now works (and the horn doesn’t), then order a new relay.

what you’ll need:

For troubleshooting purposes, you can just swap in a different relay to see if that fixes the problem. If it does, then go ahead and purchase a new relay.

The first step is to pop the hood and locate the fuse box. In the Corolla, this is located on the right side of the engine bay. as you face the car from the front.

Remove the fuse box cover.

Locate the AC relay and the horn relay (pointed to in the following image). Originally the horn relay was black, and the AC relay was white. This photo was taken after the 2 were swapped.

Swap the 2 relays. For me, the AC then worked perfectly! And the horn no longer worked. So this confirmed to me that the relay was the problem.

I ordered a new relay (part# 35874) from Amazon for less than $20. It worked perfectly and fixed my problem. The new relay was put in and the horn one moved back. AC and horn are now both working.

AC Relay (Part#35874)

Update:

It has been over 3-years since I first performed this fix, and the replacement relay is still working flawlessly!

If your AC is intermittent, and then stops altogether, another cause could be a leak in the AC system. I wrote another article that details how to solve this issue using UV dye in a Honda Accord.