How To Tell If A/C Compressor Is Running Or Not On 308? | FerrariChat

How To Tell If A/C Compressor Is Running Or Not On 308?

Discussion in 'Technical Q&A' started by donaldh2o, Jul 14, 2006.

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  1. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    143
    Irvine CA
    Full Name:
    Don
    #1 donaldh2o, Jul 14, 2006
    My '76 308 A/C is blowing warm air and I just assumed it had leaked all the R22 refrigerant. Was getting ready to disassemble the whole thing, install new O-rings, a new accumulator and convert it to R134a when I had the thought maybe the charge is okay and the compressor isnt working.

    I fired it up and I can't tell whether the compressor is running or not. The face of the compressor is so close to the engine I can't tell if the clultch is engaging or not, at least visually.

    How do I check if the compressor is switching on and off?
     
  2. miketuason

    miketuason F1 World Champ
    Owner Silver Subscribed

    Feb 24, 2006
    15,541
    Cerritos, CA.
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    Mike
    #2 miketuason, Jul 14, 2006
    Turn the key to the on position then turn on the AC switch you should here the clutch engage and disengage or see if the condenser fan is on.
     
  3. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,017
    Groton, MA
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    Verell Boaen
    #3 Verell, Jul 14, 2006
    If you stand by the pass side of the engine bay & listen while someone switches the A/C on & off w/engine running you'll hear the clutch click.

    BTW, orig refrigerant was R12, not R22.
     
  4. dade

    dade Rookie

    Jan 28, 2004
    29
    LoCo VA
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    Shaun
    #4 dade, Jul 14, 2006
    Is it not true that once the system leaks enough freon/refridgerant (ie- too low), that as a safety mechanism it is supposed to prevent the compressor from running?

    So if no freaon then no compressor, so you wouldn't be able to tell if it works or not?
     
  5. Ferrari348turbo

    Ferrari348turbo Karting

    Nov 22, 2005
    208
    Florida
    #5 Ferrari348turbo, Jul 14, 2006

    Most systems work with the low pressure cut off switch. However the low cut off switch is on the low side which is where you add freon. As soon as you pop a new can on to charge the system it will activate the low pressure switch, making the compressor work.
     
  6. rmfurzeland

    rmfurzeland Formula Junior

    Jan 7, 2005
    554
    Houston, TX
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    Ron Furzeland
    #6 rmfurzeland, Jul 14, 2006
    As well as listening for the initial click of the clutch also check the pipe coming from the compressor to the condenser (by the radiator and fan), it should feel cold to the touch.

    Here is a nice animation of the system, so you can see what parts should feel cold:

    http://www.meineke.com/services/ac.asp

    how it works:
    http://members.tripod.com/acguy2/theory_of_operation.htm#Expansion%20Devices/Orifice

    I am not sure if you have room to safely put your hand in, be careful.
    A reading from the pipe with an temperature gauge (multimeter temperature probe or wireless infrared probe) would be an alternative.
    Ron
     
  7. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    143
    Irvine CA
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    Don
    #7 donaldh2o, Jul 14, 2006
    Thanx for all the ideas guys, but I solved the problem.

    Since the initial post, I've learned that the compressor will not operate if the refrigerant is low or has entirely leaked out.

    I tested the compressor by inserting a doubled-over paper clip into the wire connections leading to the low-pressure switch (attached to the drier/accumulator). A loud click came from the compressor as the clutch engaged and the compressor seems to be running ok.

    I let it run about 5 min. and could tell the air blowing into the car was slightly cooler than the outside air and I could see the R-12 bubbling as it passed the smalll viewing glass atop the drier/accumulator.

    Guess the job now is to install new o-rings at the large hoses attached to the compressor - I was told they often dry out and leak because of all the heat they contend with in the engine compartment.

    Also will probably replace the drier, it's never been replaced in nearly 30 years. Then I'll either recharge it with R-12 or convert it to R-134a.
     
  8. rolindsay

    rolindsay Formula 3

    Jul 14, 2006
    1,022
    Houston, TX
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    Rick Lindsay
    #8 rolindsay, Jul 14, 2006
    I have a 308 that went through the same series of events, although it is now a R134a system. I will have the car in Houston within a few weeks and will have to get the A/C fixed. I am going to change the compressor our for one of the new, light-weight, higher performance Japanese models when I rebuild my system. The received-drier certainly needs to be replaced.

    rick
    '79 308GTB
    '03 L-R D-II
    '98 M-B SL500
     
  9. WaltP

    WaltP Formula 3

    Nov 1, 2003
    1,505
    Cape Canaveral/Atlanta
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    Walt P
    #9 WaltP, Jul 15, 2006
    If at all possible I would stick with R-12.
     
  10. GCalo

    GCalo F1 Veteran

    Sep 15, 2004
    7,645
    Northern California
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    Greg Calo
    #10 GCalo, Jul 16, 2006
    If you can find the lead that goes to the electric clutch, you can splice into it and insert an LED to ground. Place that up front where you can see it.

    Every time the thermostat calls the clutch to engage the LED will illuminate.

    I had an 85 733i BMW that had an A/C prob. So, I did the above and found the problem.

    I integrated the small LED into the lower dash so I could judge the time the compressor was on for proper cooling. It enabled me to adjust the thermostat for perfect cooling. I left it there and only occasionally viewed it. It was blue so as not to distract as much as red at night.

    I would discourage you from going to R134. It is not as efficient as R12, and an older system such as yours will not cool well with it.
     

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