348 air conditioning dead

Discussion in 'Technical Q&A' started by jkuk, Mar 13, 2004.

  1. jkuk

    jkuk Formula Junior

    Nov 3, 2003
    Wirral, UK
    Full Name:
    John K
    OK - a starter for 10 on where to investigate the problem.

    a/c does not work on my '91 348 TS

    system is fully charged with no leaks. - it has been pressure tested
    Compressor is working fine.

    Suggestions welcome ... although it's rare to use it in the UK

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  3. sduke

    sduke Formula Junior

    Mar 10, 2003
    The Hub City, Texas
    Full Name:
    Steven D
    First thing to check since you indicate the system is fully charged is your a/c fuses. Obviously this is a simple step but you would be surprised how much money I make off of customers too lazy to check the fuses.

    The next easy thing to check is the pressure switches in the a/c line. The low pressure switch should have continuity with the correct amount of refrigerent in the system at rest. It will open when refrigerant pressure drops past a prescribed pressure in order to prevent compressor damage from insuficient circulation of refrigerant oil.The high pressure switch has continuity until a high prescribed pressure is reached, at which point it opens to prevent overpressure damage.

    After these two steps if both check out, you need to discern if the compressor is engaging and turning properlywith the a/c on and the engine running. If the compressor is turning, a/c gauges will be needed to diagnose the pressure readings.

    If the compressor is not turning, the a/c electrical system will require additional diagnosis.

    I don't know if this helps, but at least you have a place to start.
  4. jkuk

    jkuk Formula Junior

    Nov 3, 2003
    Wirral, UK
    Full Name:
    John K

    Thanks for the tips

  5. vanimal

    vanimal Formula Junior

    Mar 19, 2003
    Full Name:
    I had a 348 challenge, a F car specialist shop that will not be referred to here spent 15 hours trying to sort it out including all the fchat tips to no avail. So all I can say is good luck, and if you find the solution please post it onFchat - the best Fcar source out there.
  6. asianbond

    asianbond Formula 3
    Silver Subscribed

    Nov 8, 2003
    Full Name:
    Does the hvac control panel come on? What doesn't work? Fan, no cold air?
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  8. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    The Brickyard
    Full Name:
    The Bad Guy
    Have you checked to make sure the wires are clean? There is a wire that is connected to the top of compressor just behind the pully. Look and see if it is clean and connected properly. The other place you may want to look is behind the control pannel inside the car. You want to make sure that everything is plugged in properly. When I first got my car I couldn't get the heater to shut off. Pulled the panel and guess what I found? The stupid control unit wasn't connected properly. Alot of the problem with these cars is bad electrical conections. So have a look and see that everything is clean and connected properly. Also you will want to look at the connections behinds the seats. They are right next to Motronic ECU's. Pop the ECU cover and you should see the 9-pin connectors. Have a look to see if those are clean and connected. Good luck let us know what happens.
  9. Lawrence Coppari

    Lawrence Coppari Formula 3

    Apr 29, 2002
    Kingsport, TN
    Full Name:
    Lawrence A. Coppari
    How do you know the compressor is working fine? The pulley always turns but you have not said if the clutch is engaged. If you are blowing fuses in your AC system, the problem is more than likely the clutch. The winding shorts out on itself over time - due to heat and vibration breaking down the shellac-type insulation of the winding.

    You could put your hand on the inlet to the condenser or the outlet of the compressor. Both should be very warm if the compressor is operating.

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