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1989 A/C Troubleshooting

 
Old 07-11-2019, 01:04 PM
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Josh Brown
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Default 1989 A/C Troubleshooting

I know there are a million topics on this but I couldnt find one that fit my car exactly. Just purchased a 1989 corvette with quite a few issues. Want some opinions or something I missed.
Brake booster is toast, ordered another, in the mail.
HVAC doesnt work. Electronic climate control unit. Compressor comes on and AC is cold, but blower will not work. Checked and had voltage at the motor connector when disconnected, but when plugged in and probed, no power, fan wont turn. Jumped 12v straight from the battery, and fan spins but pretty slowly. The fan also has power all the time even if the HVAC controls are on or off.
There is a power draw when the car is of. I checked all the suggested lights with mercury switches and unplugged them all, still a 1amp draw that I cant find from pulling fuses and unplugging stuff. I am thinking this may be connected with the HVAC system malfunction and possible blower problem.
Does the blower motor use a switched power from the resistor, or switched ground. Is it supposed to always have voltage at the motor? Is it supposed to always have voltage at the resistor?
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Old 07-11-2019, 01:34 PM
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secondchance
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Since yours is a 1989 model, I presume, it's a L98 model and not a ZR-1.
None the less;
HVAC doesnt work. Electronic climate control unit. Compressor comes on and AC is cold, but blower will not work. Checked and had voltage at the motor connector when disconnected, but when plugged in and probed, no power, fan wont turn. Jumped 12v straight from the battery, and fan spins but pretty slowly. The fan also has power all the time even if the HVAC controls are on or off.
Most likely your HVAC Fan Control module is toast. It's mounted on top of evaporator housing.
https://www.corvettemods.com/C4-Corv...hoC4wEQAvD_BwE

I had a situation where battery kept getting drained inexplicably. With the hood open, i heard a faint whirring sound. It turned out that bad fan module was feeding low voltage to the fan even with the ignition turned off. Your symptoms point to fan module failure.
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Old 07-11-2019, 04:21 PM
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Josh Brown
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Yes I was cruising around the different forums and accidentially posted in the ZR forum. My apologies, if a mod could move it that would be great.
I assume that is my issue, I just wanted to see if the fan was a switch power wire or switched ground wire through the resistor. I believe I probably need both fan and module because even with 12v the fan turns pretty slowly. Just want to cover all bases before dropping 150 on the module.
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Old 07-11-2019, 07:47 PM
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secondchance
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Originally Posted by Josh Brown View Post
Yes I was cruising around the different forums and accidentially posted in the ZR forum. My apologies, if a mod could move it that would be great.
I assume that is my issue, I just wanted to see if the fan was a switch power wire or switched ground wire through the resistor. I believe I probably need both fan and module because even with 12v the fan turns pretty slowly. Just want to cover all bases before dropping 150 on the module.
If 12v direct to the fan still turns it slow, I would be prepared for fan replacement as well. Without checking the wiring schematic, I believe 12v direct from battery to the module and module varies the voltage to the fan.
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