Corvette A/C Guru's Help Please!
Thread Starter
Racer
Joined: Nov 2002
Posts: 427
Likes: 0
From: Stillwater OK, Fun City USA
Corvette A/C Guru's Help Please!
I am having trouble with my A/C clutch. I am sure it is a problem with a module, but which one? Everything functions fine, heater works, fan speeds cycle, fans turn on when I select auto, but the compresser will not cycle. One lead of the clutch is supposed to have 12V with the key on, the other cycles the ground when all conditions are met for compresser engagement.
My problem seems to lie in the clutch ground signal. I can ground the lead and the compresser will cycle and 40 F cold air flows. If I check voltage on the ground leg, it shows 5V, instead of ground, weird!?
Does this sound like a bad blower power module? :confused:
TIA
Matt
My problem seems to lie in the clutch ground signal. I can ground the lead and the compresser will cycle and 40 F cold air flows. If I check voltage on the ground leg, it shows 5V, instead of ground, weird!?
Does this sound like a bad blower power module? :confused:
TIA
Matt
Burning Brakes
Joined: Feb 2000
Posts: 958
Likes: 1
From: SF Bay area, CA USA
Re: Corvette A/C Guru's Help Please! (Fatt Vette)
Check the pressure switch. You did not list the year of your car but on my 87 the switch is on the metal AC lines on the passenger side. Disconnect the wires to it and run a jumper wire accross them. Does the clutch engage? If it does you either have low refrigerant or a bad switch.
Thread Starter
Racer
Joined: Nov 2002
Posts: 427
Likes: 0
From: Stillwater OK, Fun City USA
Re: Corvette A/C Guru's Help Please! (weekendwrench)
Sorry, '86 with electronic controls. Tried that first thing, and I can connect my Fluke to that ground line, when I unplug each pressure sensor the weird 5V goes to zero, so the pressure switches are doing there job.
Matt
Matt
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Corvette A/C Guru's Help Please! (Fatt Vette)
I'm not sure what wire you're checking for voltage. Clutch control signal from the dash to the blower module is about 6 volts (dark green/yellow at the module). There is a 5 volt signal from the dash assembly to the low & high pressure switches - is this what you measured? - circuit is light green from the assembly to the high pressure switch & then black from the high pressure switch to the low pressure switch & black from the low pressure switch to ground on the frame near the washer reservoir. Clutch is powered by the a/c fuse (black/white) through the clutch coil & back to the module on the dark green wire. Module provides ground when it has an a/c signal from the dash assembly which it will only send if the circuit (5 volts) to the low pressure & high pressure switches are complete & there is a 5 volt signal to the ECM. So maybe its a low charge, especially if you can jumper the low pressure harness and it engages. That usually verifies that the clutch, blower module & dash assembly are good. Check resistance across the switch if you don't have a manifold gauge set. Should be less than .5 ohms. If not the charge is low or the switch is bad.
Instructor
Joined: Oct 1999
Posts: 153
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From: Cartersville GA
Re: Corvette A/C Guru's Help Please! (Fatt Vette)
If when you bypass the pressure switches and can then turn on the A/C (with the a/c controls in the cockpit) then that indicates you have a low charge. Rub a finger underneath the compressor between the pulley and the body of the compressor and tell us what comes off of it.
