I'm trying to PV my 71. When I shut the car down the ac blower comes on for 3 seconds, but it doesn't do this every time. The compressor does activate and turn-on like it is suppose to do whenever the car is shut down. Can anyone tell me how to fix this problem? Thanks.
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Re: 1971
The '71-only 'feature' of engaging the A/C compressor upon engine shutdown to add drag and thwart the potential for engine run-on with A/C equipped cars is controlled by a pair of 'smart' relays mounted to the interior A/C duct box behind the passenger side lower dash panel. Remember, the feature can only be seen to be operable if you FIRST turn OFF the A/C and let the compressor comfortable disengage before switching the ignition off.
If that's the way you HAVE been checking/verifying, then something's intermittent in your car. The most likely culprit is poor contact with the discrete ground wire in the A/C verision of the instrument wiring harness. Remember, with the two control relays attached to a FIBERGLASS structure they require a dedicated electrical ground to function! In similarly equipped '71 passenger cars, the two control relay's were mounted to the steel dash reinforcement members and didn't require a discrete ground wire like Corvette did....
So, first I'd go pull the RH lower dash pad and disconnect the relays. Clean the contact terminals and the ground spade lug and visually inspect the contact leaves in the wiring harness' connectors. These can be 'popped' out of the connector hood and individually cleaned to remove surface oxidation and foreign material (paint over-spray) that may be causing intermittent electrical contact.
Once everything is fresh/clean, re-mount and re-connect the relays and try again. If you still have intermittent operation, it's time to consider replacing your factory original control relays.... The system should fire each/every time you turn the ignition off! -
Re: 1971
Thanks Jack for the help. Does anyone know a source where I can buy the "smart" control relays Jack mentioned?Comment
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Re: 1971
Original PN's and correct mounting information is shown in your copy of the AIM book, UPC C60 Option, Sheet E9. The relays were 3996203, Anti-Diesel, and 3996204, Blocking.
I think I'd check with Chevy to see if these are still available or if they've been discontinued before going elsewhere. If memory serves, one or both may be in the Dr. Rebuild Catalog. If all else fails, you'll find them under the dash on certain '71 Chevy passenger cars that also used them (Chevelle and full sized Chevy wagon are two examples)....Comment
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Re: 1971
Once again Jack thanks for your help, I greatly appreciate it. JohnComment
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