Need help AC diagnosis - Chevy Impala SS Forum
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post #1 of 3 (permalink) Old 08-15-2016, 07:23 PM Thread Starter
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Need help AC diagnosis

I had cold AC. I installed the primary fan wiring harness from Innovative wiring, fans operate as they should but AC blows hot now.
The compressor is running and the drier/accumulator gets cold.
Gauge reading is Low Side-45 PSI, High Side 250 PSI at ambient 109*F and 16% humidity.
Gary at innovative wiring said he has not heard of this happening before.
I thought I may have shorted out my wrench on the high side line when I was disconnecting the positive batt cable but the ground cable was already detached. AC fuse looks good.
I know its not simply low freon because there would have been a gradual decrease in cooling and the compressor would cycle. Something related to the fan install.
Any ideas?
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post #2 of 3 (permalink) Old 08-15-2016, 08:55 PM
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Does the accumulator get as cold as normal? If so, I would think that the only explanation is that the vent has moved to the heat setting for some reason.

I'm not the smartest guy on the forum, but I think the vent is controlled by vacuum.

Try turning on the heat, and see if you hear the vent move. Then back to A/C...

Just a suggestion. Hopefully someone smarter will respond.

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post #3 of 3 (permalink) Old 08-16-2016, 08:37 PM Thread Starter
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I disagree. You are the smartest guy on the forum. Your suggestion proved to be correct. I found this diagram-

1994 Buick Roadmaster LIMITED A/C & HEATER MODULE ASM

Then observed actuators #30, #31, and #32 in action. Actuators 31 and 32 move between defrost, middle, and floor and are vacuum controlled.

Actuator #30 controls the door between the heater core and the evaporator coil. It is electric with no vacuum assist. The internals are plastic gears and one of the plastic cogs cracked.

Gary's wiring harness is top notch and I highly recommend. It had nothing to do with my loss of AC. I think what happened is when you disconnect the battery the HVAC controls cycle through the settings (at least on a RMS with auto climate control) and incidentally the actuator cracked during the reset.

Luckily gravity puts the default setting of the door in the AC position if you remove the actuator so I've got ac until I get a new acuator.

Anyone else out there considering doing this its super easy. Just remove the glove compartment and ashtray to get a look at the actuators while you move through the controls. #30 has a slotted steel sleeve that should move between the 11 o'clock and 1 o'clock position. 11 o'clock is heat and 1 o'clock is ac.
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