A/C compressor

[Druseph T. Justice]

So the other day was the first time it's been warm enough to test a/c since I bought the car. I turn it on and..... Nothing. Ambient temp coming through vents. Pop the hood and see that the compressor is not spinning. Anybody know of a common problem with the compressor/clutch not engaging?

I'd GREATLY appreciate any help. Summer is here and a black car with black leather is no fun without a/c. Thanks.

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[r1crusher]

Not sure if the compressor will kick on if say it were low on refrigerant. You could check the line pressures but you'd need the proper gauges. That would tell you if it's got any in it at least and if there's enough to pressurize the system.. Short of that, fuses or relays that control the a/c could be checked.

Someone else I'm sure can provide more info for you.

 

[SHO-flames]

I had a similar problem in my 2011 SHO. I was told by the dealer that the cause was the result of a small leak along the seam of the radiator for the A/C refrigerant. I assume poor workmanship from the original supplier as I have owned the car from new and have never hit anything - although I always wondered if it was damaged when the dealer did a recall on something to do with the radiator fans. Anyway it was replaced under warranty. They will typically check for leaks first when the A/C stops working using a special dye. Hope the fix is easy and inexpensive.

 

[Druseph T. Justice]

I had a similar problem in my 2011 SHO. I was told by the dealer that the cause was the result of a small leak along the seam of the radiator for the A/C refrigerant. I assume poor workmanship from the original supplier as I have owned the car from new and have never hit anything - although I always wondered if it was damaged when the dealer did a recall on something to do with the radiator fans. Anyway it was replaced under warranty. They will typically check for leaks first when the A/C stops working using a special dye. Hope the fix is easy and inexpensive.

Thanks. Mine is an 11 as well. Too bad I've only got power train warranty left on it. Although I think I could handle a radiator replacement myself if need be.

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[Druseph T. Justice]

Update: I went out and bought a recharge kit with a gauge on the hose. Before attaching to the refrigerant can I checked the pressure (low side) and it immediately maxed out the gauge, which maxes at 100psi.

The kit was pretty cheap, so I'm not sure on the accuracy or reliability of the gauge. But I didn't try to add any refrigerant. Now obviously the system has refrigerant and pressure, probably too much pressure depending on the validity of the gauge. So it's probably not a low pressure switch keeping the compressor from turning on. I'm thinking it's probably a bad wire or relay/fuse somewhere, which I will search for tomorrow. Does anyone know if there is a high pressure switch that prevents the compressor from running if system pressure is somehow too high? And also, how would the pressure get so high? I think the green zone on the gauge was like 30-60psi. Do the ac systems on our cars run higher pressure than most?

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[SilverSH0]

And also, how would the pressure get so high? I think the green zone on the gauge was like 30-60psi. Do the ac systems on our cars run higher pressure than most?

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When you were testing was the compressor kicked on?

If you read the side of the can I would be willing to bet it tells you to turn on MAX AC or jumper the low pressure switch. This is to keep the compressor engaged so that the dial reads the correct pressure. If the compressor is NOT running there's nothing in the system to build a pressure head so the entire system will be at the same pressure. But once the compressor kicks on it will build a pressure head and cause high pressure on the high side and then there will be low pressure on the low side. In order for that gauge to read correctly the compressor needs to be engaged as that's how it's designed.

To answer your question, I would imagine the compressor was not on and that's why the pressure was so low on the low pressure side of the system (it would read the same on the high pressure side).

 

[Druseph T. Justice]

When you were testing was the compressor kicked on?

If you read the side of the can I would be willing to bet it tells you to turn on MAX AC or jumper the low pressure switch. This is to keep the compressor engaged so that the dial reads the correct pressure. If the compressor is NOT running there's nothing in the system to build a pressure head so the entire system will be at the same pressure. But once the compressor kicks on it will build a pressure head and cause high pressure on the high side and then there will be low pressure on the low side. In order for that gauge to read correctly the compressor needs to be engaged as that's how it's designed.

To answer your question, I would imagine the compressor was not on and that's why the pressure was so low on the low pressure side of the system (it would read the same on the high pressure side).

It was not on. I checked all the fuses and relays pertaining to AC earlier and they were all fine. Any tips for bypassing the pressure switch on these cars? Just from looking at the compressor, I'd imagine it's easiest to access from underneath. Or maybe trough wheel well with the wheel and inner fender removed.

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[SilverSH0]

It was not on. I checked all the fuses and relays pertaining to AC earlier and they were all fine. Any tips for bypassing the pressure switch on these cars? Just from looking at the compressor, I'd imagine it's easiest to access from underneath. Or maybe trough wheel well with the wheel and inner fender removed.

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These cars are a lot more involved in terms of computers and feedback loops. I would start by looking at wiring diagrams and determining how it works. But on other vehicles I've worked on you could either short across the low pressure switch or pull the AC clutch relay and jumper it. My guess is these cars have a pressure switch that's more advanced and has more than 2 wires. So I would likely go to the relay and jumper it to see if it kicks on the clutch.

Again, I haven't looked at the specifics of this car so make sure you look into it. I'm talking in general terms that has worked on past vehicles.