A/C help....general

Ok...its a 2009 ford expedition with high mileage.

The other day the AC just randomly stopped working. It was blowing fine the day before.

I checked all associated fuses and relays. They all tested good.

The compressor will simply not cycle on. I know that could be the cause of a bad compressor a bad electrical connection or a pressure switch protecting the compressor.

I put a manifold gauge set on the system. Both while the engine was off, and while the engine was running the pressures on both the high and low side read approximately 65psi. Temperature was 85F-90F.

Just for grins and giggles, I put a vacuum on the system for a good 45 minutes. Shut it off and it held -29.9 inches fine...25 min or so later I decided to charge the system with the hope that the switches would now allow the compressor to cycle on.

As the pressure rose on the low slide the high side pressure slowly raised as well but with a slight lag and never really caught up. The pressure stabilized at 65 psi on both sides, the compressor never kicked on. Yes, I made sure I was only charging via the low side and the AC was on full blast with doors open....temp of the air never dropped as the compressor never kicked on.

What do you think?

 

I'm no expert, but I would check the compressor clutch. If it's not working then the compressor will never even try and kick on.

 

So I finally found the pressure switch. Checked the connector that plugs into it and I'm getting about 5 volts on two of the wires and about 3 on the third. I plugged it back in....

Then I went to the compressor I unplugged it. I put my voltmeter across the connector that plugs into it. When I had the wife turn the AC on I showed 14 volts across it. When I had her turn it off it showed 0 across it.

So at this point I'm thinking it's the AC clutch? The thing seems to be getting power but it's not working.

 

Try giving the clutch a tap with a screwdriver or something to see if you can get it to stick. That's an easy way to check to see if the gap has gotten too large. Car needs to be running with ac "on". Just watch out if it does stick because it can kick the screwdriver back at you.