Dean_Fuller

Have not used the A/C for about 8 months now because of a bad blower. Just replaced that blower yesterday and now my A/C in not working. I remember jumping the compressor to "pull" freon but now cant remember how. I have done a few searches without a clear answer. Can someone refresh my memory?

chrly924s

You have to bypass the low pressure switch.

chrly924s

If it's low on gas, you have to bypass the low pressure switch

chrly924s

If it's low on gas, you have to bypass the low pressure switch

Dean_Fuller

Thanks Charly.... I cannot remember how though. Do I just ground the switch?

dprantl

Sounds like you are expecting it to work after you jumper the compressor. If the system is low on freon and you run the compressor too long, you will damage it. So... you either have an electrical/mechanical problem or you are low on freon.

Dan
'91 928GT S/C 475hp/460lb.ft

dprantl

I *think* you just disconnect and jumper the contacts together. I never did it this way, I just disconnect the clutch wire and apply +12 directly when troubleshooting.

Dan
'91 928GT S/C 475hp/460lb.ft

chrly924s

What he say!!

dr bob

Dean--

Jumper the switch by pulling the connector, then us a jumper with to bridge the two terminals in the harness connector.

Be sure that the car is actually low on freon before you add more. A lister recently phoned for charging instructions, and added freon only to find that the compressor still would not run. Ended up overcharging a bit.

----

If you are using the small cans to fill, be sure to purge the air from your manifold and charge hoses before you open the valve from the can. Remember also that you can add freon to a cold system without running the engine and compressor at all. To do this, charge with liquid from the can by inverting the can so the hose connection is at the bottom. Hold the can in your hands for a few minutes to warm it, then open the valve to allow the liquid to flow into the car. You can add a little more heat with a bucket of hot water from the tap. Just be sure to keep the hose connection at the bottom so only liquid flows from the can. Let the car sit for five minutes minimum before you run the compressor to make sure that the liquid has flashed completely into vapor. Car and system can not be hot for this to work, by the way.

Dean_Fuller

Well last night I jumped the 2 connections in the switch together and all I got was sparks....no compressor action. I'm living out of a suitcase right now so pulling vaccum is hard to do right now. I did all this 8 months ago and all was well then. I guess I will see.

Thanks

Giovanni

is the compressor wire connected? If that comes loose you won't have power to the compressor and it won't come on even if you bypass the switch (if I am not mistaken).

Mrmerlin

to check the compressor disconnect the wire lead that goes down the front of the engine and with a jumper wire connected to the wire from the compressor tap it on the hot post. this will engage the clutch

Bill Ball

Hi Dean:

You're jumping the low pressure switch harness plug, right? Not the switch itself. If you got sparks in the harness plug, that means that at least it has 12V flowing to it, which is good, as that rules out the freeze switch, climate control and wiring up to that point. When you do this jump, with the ignition on, AC switched on, motor running or not, you should hear a decided "click" as the AC compressor clutch engages. If not, check the connection of the AC clutch wire to the front engine harness, usually accessible near to the air pump. That may have come apart. You should check for 12V coming from the harness there. If it has 12V, but the clutch still does not engage, apply 12V to the clutch wire using a jumper wire from the charge post. If that works, then it is possible the climate controller is not providing enough amperage to engage the clutch. If it still doesn't engage, the clutch coil is probably bad.

Dean_Fuller

After rigging a better jump wire I CAN get the clutch to engage but it stops as soon as the wire is removed. I guess I REALLY NEED to pull a vaccum...can I get some help at SITM this weekend????

dprantl

- Start the car
- While it is idling, turn on the blower inside to position '1' and feel the air temp
- Go under the hood and jumper the A/C clutch wire for 10 seconds. Don't do it any longer than this
- Disconnect the jumper, then quickly jump into the car and feel the air temp

If it is cold, then your freon level is fine and you need to track down the electrical problem.

Dan
'91 928GT S/C 475hp/460lb.ft