AC compressor test

[VAhasnoWAVES]

trying to make sure the clutch on my compressor is working properly. playing with the switches in the dash doesnt do anything to it. i was wondering if there was a way to "jump" it and test it.

 

[BrokenSockets]

You can do a few things - jump power direct to the compressor clutch, jumper the low pressure switch, could also be the shim in the clutch preventing the clutch from engaging.

I think there are many threads for AC problem diagnosis - I found all the info I needed here with various searches and was able to diagnose a broken wire and a bad relay to get my cold air back last year.

The answers are in here - sorry I have no links for you but you will find them with the right search words.

 

[Shorty]

clutch coil is grounded to the compressor case, so all you've got to do is take the single wire that's plugged into the engine harness and apply 12+ volts. The coil should pull the clutch plates together and the compressor should turn.

don't leave it running for too long, though until you figure out why it's not engaging with the normal controls. If it's low on refrigerant, you can kill the compressor from oil starvation rather quickly.

 

[VAhasnoWAVES]

NOT trying to repair the AC. it hasnt worked in a good while.

clutch coil is grounded to the compressor case, so all you've got to do is take the single wire that's plugged into the engine harness and apply 12+ volts. The coil should pull the clutch plates together and the compressor should turn.

don't leave it running for too long, though until you figure out why it's not engaging with the normal controls. If it's low on refrigerant, you can kill the compressor from oil starvation rather quickly.

the system is void of freon. it has been for years. i understand internally the compressor may be shot, but ive got another one laying around if that is the case. i just need to make sure this one is functioning properly before i start my OBA build. jumping it for a few seconds to check that its sucking/pushing air shouldnt hurt it any.







is the reason its not working when i play the the AC switches in the dash because there is a safter switch or pressure switch of sorts somewhere that is keeping it from engaging?

 

[whitexj98]

If there is no refrigerant in the system then the low pressure switch is open not allowing the compressor on, you can simply jump the switch to see if it still works.

 

[87manche]

N
is the reason its not working when i play the the AC switches in the dash because there is a safter switch or pressure switch of sorts somewhere that is keeping it from engaging?

yes, look for a sender looking thing with two wires on the low pressure side. Jumper the two wires to bypass it. It senses that there's no refrigerant pressure and kills the power to the clutch so you don't lock up the AC compressor when your evaporator leaks.

at least it was two wires on the 87.

 

[UNCC_99XJ]

On a late model, the low pressure switch is on the Accumulator (also called Receiver Drier), which is mounted right in front of the firewall.

On early models, the Accumulator is mounted below the compressor, and I don't recall if the low pressure switch is stuck to the top of it like the later models or if it's on the compressor itself. Been a while since i've done A/C work on an early model.

 

[VAhasnoWAVES]

so i finally got around to this... lol.

On a late model, the low pressure switch is on the Accumulator (also called Receiver Drier), which is mounted right in front of the firewall.

On early models, the Accumulator is mounted below the compressor, and I don't recall if the low pressure switch is stuck to the top of it like the later models or if it's on the compressor itself. Been a while since i've done A/C work on an early model.

while i was removing everything preparing for OBA i figured this was the switch but a paper clip yeilded no effect. should that simply do the trick or is there a proper way to jump it?

 

[UNCC_99XJ]

so i finally got around to this... lol.



while i was removing everything preparing for OBA i figured this was the switch but a paper clip yeilded no effect. should that simply do the trick or is there a proper way to jump it?

I've always used a paper clip or some wire (any wire, even speaker wire will do). Just have to make sure the clip or wire is making good contact on both sides inside the connector.

If you're positive you have a good connection jumping the switch, and it still doesn't come on, then the problem is elsewhere.

 

[whitexj98]

You do have the A/C set to on when your trying to jump it right?

 

[Shorty]

clutch coil is grounded to the compressor case, so all you've got to do is take the single wire that's plugged into the engine harness and apply 12+ volts. The coil should pull the clutch plates together and the compressor should turn.

I'd still use a jumper from the B+ terminal just to verify the clutch and compressor will function. Eliminates any other sources of poor connections, switches, or fuses from the equation.