Why does the A/C compressor run continuously?

Neil,

Low Freon won't cause this. My first guess would be the compressor relay is stuck and needs to be replaced.

I attached the wiring schematic below. It was one page, but I cut it in half, so you read it. I did overlap the two so you can follow from one to the other.

Here is what I need you to do: Pull the A/C relay in the under-hood fuse box. See if the compressor turns off. If it does, I would normally tell you to switch it with a different relay having the same part number. However, if I am correct and the relay failed internally, it will send power to whatever component you switch it with. So, let's just test the relay.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below. Pic 3 shows the relay.

Hi,

When you checked 85 and 86 was the relay installed? If the relay was out, only one side should have had power. You also mentioned that power was there when the A/C or one of the other modes was requested. So, I'm not sure if there was power at any other time.

As far as it running at all times, the system should turn on when the high side pressure sensor signals a drop in pressure, indicating the compressor needs to run. So, in theory, you could be low on Freon.

Also, if the compressor clutch overheated, it could simply be stuck. If you remove the accessory drive belt, see if the pulley spins freely. Obviously, everything needs to be turned off for this.

You indicated the high-side pressure sensor is good. If neither the high side pressure nor the A/C clutch are an issue, chances are you have a short to power at some point before the relay which is causing the relay to stay energized.

Let me know if you are able to check the things I suggested.

Take care,

Joe

Hi,

If you had power on both pin 85 and 86 with the relay removed, that doesn't make sense. One should have power and the other is open until a ground path is provided to actuate the relay's secondary switched side.

If you have power to both, that indicates the PCM isn't providing ground, but instead, it is sending power. That would indicate a short to power. I may ask you to disconnect the connector at the PCM and inspect the connection pins.

I may have misunderstood what you meant, so let me know.

Joe

Hi,

At this point, I think that's a good idea. Let's see if it appears we have a low/weak charge.

Let me know what you find.

Take care,

Joe