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  • Electrical: AC System

    I recently purchased my first Avanti. RQB-1659 has been expertly maintained for the past 31 years by Randy Atkin. The car is near perfect. Now I get to have all of the fun of doing my best to keep it that way.

    The only issue with the car is the AC not working. I took it to a friend to have the system checked out. He evacuated, oiled & recharged the system. But, no AC Comprsr clutch engagement. We ran 12v to the clutch and checked out the system and it produced ice cold air into the car .... good deal! But, no power to the wire to the AC Comprsr clutch.

    I opened up the center stack. The On-Off Fan switch works as it should. The Temp switch (P/N 1552650) is wired correctly as I see it. Could this part be at fault by not applying the needed voltage to the AC Comprsr clutch? Not sure where to go next. Any help on this would be much appreciated.

    Thanks, Harv
    StudeBakerHarv
    * 1950 Champion Starlight Coupe (Cathcart Stg 4 Engine).
    * 1971 Avanti II (RQB-1659).
    * 1960 Lark Regal VIII Convertible.

  • #2
    Harv,

    If your control is wired the same as mine, there should be a yellow wire to the center lug of the fan switch. This supplies the 12V. There are two black wires. One has variable voltage (as the knob is turned) to the fan motor to regulate the speed. The other is a jumper to the thermostatic switch. This wire should have the full 12V any time that the fan switch is on, regardless of fan speed. Looking at the back of the switch, with the yellow wire above the others, the jumper to the thermostat should be on the lug that is below and to the left of the yellow. The wire to the fan is on the lug below and to the right of the yellow.

    The brown wire from the thermostat powers the compressor clutch and the throttle kicker solenoid. You can test the thermostat with the power off using two cups of water, one lukewarm, and one with ice. Dip the end of the sensor tube in the ice water for about 20 seconds. Then dip it in the warm water. You should hear a click as the switch closes. Then reverse the procedure, and you should hear a click as the switch opens. If it doesn't click, you have a bad thermostat. If it clicks, try the test with the car running. The compressor clutch should engage with the warm water. If not, you may have bad contacts in the switch. Take a volt meter, and check that you have 12V coming to the thermostat from the fan switch when the fan is running. If not, there could be a bad contact in the fan switch itself. If there is 12V on the jumper lug, but nothing on the brown wire lug, pull the brown wire off of its lug and touch the brown wire to the jumper from the fan switch. If the compressor clutch engages, you've got a bad thermostatic switch.

    The thermostatic switch is a generic unit, not unique to the Avanti. I bought one on line last year.

    Good luck.
    Last edited by Rerun; 05-21-2012, 05:24 AM.
    Jim Bradley
    Lake Monticello, VA
    '78 Avanti II
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    • #3
      The vendor that I found was
      http://www.nostalgicairparts.com/
      The part number that I used was 119-9921 Rotary Thermostat 24 inch capillary probe $19.99

      Here's what the control wiring looks like on my Avanti.

      Click image for larger version

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      Jim Bradley
      Lake Monticello, VA
      '78 Avanti II
      sigpic

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      • #4
        Jim,

        Thanks for your expert guidance and the detailed photo. The wire colors on my '71 are a bit different than on your '78 but that didn't matter as I used your instructions to help find the problem. It turned out that the wire to the center lug of the fan switch didn't have 12 volts on it. It was the brown fan wire that was plugged in there. The 12v power wire (mine is black) was plugged into the lug for the fan wire. Once I saw where the 12v was at I just swapped the two and now everything works as it should. Maybe someone swapped them so that they could use the fan without turning on the AC Comprsr with a low charged system. I now have a Cool Avanti !!!! Thanks so much for your help Jim. Also, I'll be sure to make note of the nostalgicairparts.com site for future needs and info sharing.

        Regards, Harvey
        StudeBakerHarv
        * 1950 Champion Starlight Coupe (Cathcart Stg 4 Engine).
        * 1971 Avanti II (RQB-1659).
        * 1960 Lark Regal VIII Convertible.

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