A/C seems to be always on?

Hi,

The compressor should not be engaged at all times. When the AC is requested, the compressor should cycle on and off. When the defroster is on, the same thing will happen. When you only request the vent (fresh air) it shouldn't be on.

As far as the lighting dimming when you turn the blower motor on, it isn't uncommon simply because you have added a larger load to the system. However, I don't know to what extreme you are experiencing.

Here is what I need to know. If you start the truck, turn on the blower motor and have vent only selected, does the compressor engage?

Let me know.

Joe

Yes, the compressor engages after starting the truck.

The relay may have shorted. Pull the AC relay and switch it with one having the same part number to see if it changes things.

If there isn't one, here is a link that explains how to test one:

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

Let me know what you find.

Joe.

See pic below for the compressor relay location.

I went to the Ford dealer got a new A/C relay and there is no change.

Does the compressor engage with the relay removed? If it does, there has to be a short to power. If it doesn't, we need to check the terminals where the relay connects. Something is allowing power to make it to the compressor at all times.

Joe

I had my son watch the compressor it engaged most of the time when I turned the fan on a few times. Did not engage when the relay was taken out.

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Outlaws are Wanted.

Hi,

Good one. LOL

If the compressor continues to get power, we may have a PCM providing a ground path to actuate the compressor clutch or a short to ground.

I attached the wiring schematics below for the AC circuit, so you have a reference.

Here is what I want you to test. Remove the compressor clutch relay. There are 4 pins. The wire in question will be white with a brown tracer. It will be either pin 85 or 86 identified. If you find it has power at all times, check the opposite pin.

The white/brown wire goes to the powertrain control module. The PCM provides a ground path to that wire when the AC is requested. Once the path is provided, an electro-magnet in the relay closes the connection between pins 87 and 30 to send power to the compressor.

So, I need you to check if the white/brown wire has continuity to ground with the key on and AC requested. If it does, turn the AC off and see if it still has ground. This will determine if there is a short to ground or if there could be an issue with the PCM.

Let me know the results.

Take care,

Joe

See pics below.

I had my mechanic friend do the checking and could not find anything. The AC does not work in the vent or feet position. We think it might be in (behind) the on off switch itself.

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All the DNA is the same and there are no dental records.

LOL Like the joke.

Does the compressor turn off if you disconnect the switch? It should, and the switch itself does make sense. You could also check for continuity through the switch in both the on and off position to see if the circuit is constantly completed.

Joe

My mechanic friend put a new switch in and there are no changes with the A/C being on when not needed. Not running in vent or floor. Do I write to Ford to see if this to be normal or not?

Hi,

The idea that it continues to run indicates it is getting power. Where it comes from is the question.

Have you tried removing one fuse at a time to see if there is one that turns it off? By the way, thanks for making me laugh. I needed it. LOL

Joe

Check out this channels video - https://www.youtube.com/watch?v=FBORpcuhXX8