A/C electrical help needed
Thread Starter
Intermediate
Joined: Jan 2000
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From: Grand Prairie
A/C electrical help needed
I have replaced both the head unit and A/C programmer in my 1990 Corvette. Good news is I now have functionality on my head unit. Bad news no air blowing. I was told to charge the system as it was low. Pulled a vacuum and charged to about 90. As freon started to go in compressor clutch started to kick in but soon stopped. After some basic troubleshooting, here is where I'm at. I have checked all fuses and are fine. There is power to blower motor, but no air blowing, not even on vent. Compressor clutch engages if jump with power from battery. There is no power to or from Low pressure switch and therefore no power to compressor. Having trouble finding where I'm losing power. Also not sure if I have a bad blower motor, becuase I thought I would atleast get hot air blowing. Any help would be appreciated.
Thanks,
JamesG
Thanks,
JamesG
Le Mans Master
Joined: Dec 2000
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From: San Diego, Ca
Re: A/C electrical help needed (JamesG68)
I don't know what you mean when you say you charged to about 90 - pressure with the compressor off? If so, that would be enough to close the low pressure switch and start the compressor, but if the charge is low, the low side could drop below what's necessary to keep it running. Power to the low pressure switch is through the high pressure switch on the high pressure line, so make sure it's closed. If so, & the low pressure switch is closed with the compressor off, charge is probably too low. Jumper the low switch harness with a paperclip, disconnect the main fan switch to keep it running, hold rpms steady at 1500, and then charge until the high side pressure reads 2.2 to 2.5 the outside air temp; ie, on a 70 degree day, 154 to 175 psi. You may also want to verify the compressor ground circuit at the blower module. Power is supplied to the compressor by the a/c fuse. Disconnect the lead at the module from the compressor and ground it. Clutch should engage. If not, the module may be bad, but you need to make sure the charge is right first.
Racer
Joined: Jun 2003
Posts: 433
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From: Aspenden Hertfordshire U.K.
Re: A/C electrical help needed (JamesG68)
I am sure youve tried it , but have you"reset" the system ? this needs to be done after a recharge . Remove the courtessy and radio fuses for about a minute then replace . Best of luck Mike .
Le Mans Master
Joined: Jun 1999
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From: Chino Valley AZ
Cruise-In I Veteran
Cruise-In II Veteran
Currently Corvette-less
Re: A/C electrical help needed (autocolor)
:iagree: Autocolor nailed it. I found you need to disconnect the battery for a few minutes to reset the system. Pulling a fuse will work also. I always have a can of freon hooked up and flowing into the system when I start the A/C. That way if the system is low, it will satisfy the low pressure switch and keep things running until you get the correct charge.
~ Purp
[Modified by PurpleC4, 8:13 AM 6/8/2003]
~ Purp
[Modified by PurpleC4, 8:13 AM 6/8/2003]
Thread Starter
Intermediate
Joined: Jan 2000
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From: Grand Prairie
Re: A/C electrical help needed (SunCr)
I will try the "reset" thing, but think I may have narrowed down my problem. Using the wiring diagram in the service manual, I seem to have found an issue with the A/C clutch relay. Since I had no power at the low pressure switch, I checked the high pressure switch and it did not have power either. According to the wiring diagram power comes from the A/C clutch relay to the high power switch. When I checked the A/C clutch relay the two brown wires are hot, however the green wire that is supposed to go to the high pressure switch is not. If I jump power to this green wire then everything is hot and compressor clutch kicks in. I tried replacing that relay but still not hot on that green wire. I am now having trouble understanding why that green wire is not hot. Is there something more to the relays than replacing them? Thanks again for all the help and advice. I am definitly getting closer to nailing this thing.
