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1987 328 A/C question

Discussion in 'Technical Q&A' started by brent Lachelt, Sep 8, 2004.

  1. brent Lachelt

    brent Lachelt Formula 3
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    I just had my a/c recharged with freon R12. The system is holding the charge with no leaks. My question is that it only blows at 60 degrees. My 308 used to blow at 45 degrees. The 328 is a new car for me and I'm not sure if that temp is OK or is there something else that could be a problem. Right now the fan only blows on high. I need to fix the switch which according to some of the research could be a couple things. I'm going to tackle that later. York compessor is what is in the car.
     
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  3. Ferrari_tech

    Ferrari_tech Formula 3

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    Brent,

    Couple of things to check, firstly is the fan working that cools the gas in the condensor, it is controlled by a bimetallic thermoswitch (# 9) which is clipped onto the lower pipe on the condensor (the switch is known to suffer from corrosion where it attaches to the pipe) it is easily removed and cleaned.

    Secondly the thermostat control switch in the consol could be faulty.

    The problem with your fan speed only working on max is more than likely the power transistor (#13) in the picture.
     
  4. brent Lachelt

    brent Lachelt Formula 3
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    Thanks for the reply Malcolm. I have a couple questions. I'm going to check the condensor fan today. If it is working correctly does it turn on as soon as the a/c is on, or does it have any type of sensor switch like the radiator fans. Secondly how much is a new thermostat control switch if I need one? I noticed at night the light underneath that switch doesn't work. Is that a separate piece or part of the switch. I saw the steps with pics on how to change the power transistor in the archive website. Going to get to it soon.

    Thanks
    Brent
     
  5. Ferrari_tech

    Ferrari_tech Formula 3

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    Brent,

    The fan doesn't come straight away, it should only come on when the sensor (#9) senses that the gas is getting warm.

    The thermostat switch costs £51.00, sadly we are out of stock.

    From memory I recall that the illumination for the switches is a small bulb held in it's holder whichis fitted on top of the switch.
     
  6. brent Lachelt

    brent Lachelt Formula 3
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    Malcolm, the bimettalic thermoswitch was very corroded including the suface that presses against the lower condensor pipe. The clip was very rusted. I'm cleaning it all now. If the sensor wasn't working, because of the corrosion, does that mean the fan wouldn't turn on when the gases got hot? I guess I could have tested to see if the fan worked first, but once I saw all the corrosion I wanted to dig in and clean it up. I let you know what happens.
     
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  8. Ferrari_tech

    Ferrari_tech Formula 3

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    [If the sensor wasn't working, because of the corrosion, does that mean the fan wouldn't turn on when the gases got hot?


    Correct, as said it's quite a common fault - hope this fixes for you
     
  9. brent Lachelt

    brent Lachelt Formula 3
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    Malcolm, The A/C blows at just above 42 degrees! Thanks for you help. I'm going to start on the power transistor next.

    Thanks Again
     
  10. brent Lachelt

    brent Lachelt Formula 3
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    Malcolm, got motivated and replaced the power transistor. The a/c still only blows on high though. I think it may be the air volume control switch. Do you have those in stock?

    Brent
     
  11. Ferrari_tech

    Ferrari_tech Formula 3

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    Hi Brent,

    Glad the "fix" on the sensor has improved the a/c temperature, although am surprised that the power transistor didn't fix the fan speed (it could be the switch, but 9 out of 10 times it's the transistor)

    It may be a good idea to double check the wiring on the power transistor, I will briefly explain where the wires go (not enough room to post the entire wiring diagram so have just shown the power transistor [#106] and the evaporator blower [#105]

    Power Transistor has three wires - terminal B (orange / red) goes to the fan speed switch. Terminal E (yellow / green) goes to ground. Terminal C (green / red) goes via the evaporator blower to terminal 30 on relay C on the auxillary relay board [#75].

    One small problem, Ferrari have in the past changed the colour coding of the wires without amending the manuals so don't be surprised to find some differences.

    Lastly, not sure what you mean by the "air volume control switch" - if you are refering to the a/c fan speed switch then I'm affraid we are out of stock.

    Hope all this helps
     
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  13. brent Lachelt

    brent Lachelt Formula 3
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    Malcom,

    I'll play with the wires a bit more before I give up on the power transistor and replace the a/c fan speed switch.

    Thanks
    Brent

    PS. Is there a way to test the power transistor it self to see if it is OK or not?
     
  14. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Brent -- The functional test for the a/c fan speed switch is to measure the current flowing in the Orange/Red (CR) wire going to the "B" (base) terminal of the power transistor. It should change quasi-linearly as you turn the a/c fan speed control knob from min to max:

    1. If it doesn't -- then either the a/c fan switch is bad, or your (new) power transistor is bad, or the connection from the "E" (emitter) terminal to ground is bad, or a needed supply voltage is missing, etc..

    2. If the base current does behave OK, but the fan motor still doesn't run -- then the a/c fan switch is OK and your problem is elsewhere.

    Just wanted to suggest this test before you spend the big $ for a new switch (i.e., if case #1 it doesn't really pinpoint the problem, but if case #2, then replacing the a/c fan speed switch will make no difference so it would be a waste).

    Another quickie check (with the system "on" and the fan speed switch set to a "mid" position) is to use a (large) jumper wire to connect the "E" terminal directly to the "C" terminal on the power transistor (or at the connector jumper from the yellow/green GV terminal to the green/red VR terminal):

    3. If the fan runs full speed -- then that confirms that much of the wiring is OK.

    4. If the fan still doesn't run -- then that confirms that you definitely have a wiring/connection problem somewhere.
     
  15. brent Lachelt

    brent Lachelt Formula 3
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    Steve, When you say "large jumper" wire do you mean taking two metal clips with a wire between them and clip one to terminal E and one to terminal C? Also just to confirm the back of the transistor only has two wires/terminals out the back terminal E and B. Terminal C is a screw that goes through the mounting plate and the green/red wire is attached to it.

    Thanks
    Brent
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
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    It's really more just momentarily "touching" a wire from terminal "E" to terminal "C" (which is really the transistor case itself as you noted -- and is why the transistor case needs to be "insulated" from its mounting bracket). The current will be like 8~10 Amps so you don't want to use a 30 gauge wire -- but anything 18~16 ga or larger is OK as long as only for a few seconds.
     
  17. brent Lachelt

    brent Lachelt Formula 3
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    Thanks Steve I'll try it and let you know

    Brent
     
  18. brent Lachelt

    brent Lachelt Formula 3
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    Steve,

    I did the quickie check:

    Another quickie check (with the system "on" and the fan speed switch set to a "mid" position) is to use a (large) jumper wire to connect the "E" terminal directly to the "C" terminal on the power transistor (or at the connector jumper from the yellow/green GV terminal to the green/red VR terminal):

    3. If the fan runs full speed -- then that confirms that much of the wiring is OK.

    4. If the fan still doesn't run -- then that confirms that you definitely have a wiring/connection problem somewhere.

    --------------------------------------------------------------------------------
    Last edited by 91tr : Today at 08:16 AM.

    As it turns out the fans do run at full speed when this done. So I guess that means it is a bad new transistor or a bad a/c switch?

    Brent
     
  19. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Yes, but try the base current test too -- it may help with the decision:

    If the base current behavior is bad -- then either component (or the upstream power supply) could be bad, but

    if the base current behavior is OKish (and still no fan action) -- then I believe that you can conclude that the problem is in the (new) power transistor.
     
  20. Lawrence Coppari

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    Try squirting some contact cleaner down the shaft of the speed knob. Mine did this a couple of years ago. It would only run at high speed. Dirty switch caused my problem.
     
  21. brent Lachelt

    brent Lachelt Formula 3
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    Well once again I have all of you friends at ferrari chat to thank! Steve and Malcolm. I remembered several weeks ago that someone told me that the control switches for the A/C are the same as the ones for the heater fan switches. At the time I swaped them and the A/C still only blew on high. So thats when I started looking at the power tansistor. The one thing I hadn't done was try swapping them again after I changed the transistor. Well guess what? I did and now I have variable speed A/C!! So not only was the power transistor bad, but so was the switch. When I connected the A/C switch to where the heater fan switch connected it ran constant and when you clicked the switch off the heater was still running. Something definitely wrong with that switch. Lawrence, I got your message after I put everything back to gether. Someday soon I will try what you suggested before I buy a new one. I just left the right side heater fan switch (formerly the A/C switch) in place , but not connected. It's 100+ degrees in So Cal don't need the heaters anytime soon. So now the A/C blows cold and at high and low speeds. I wonder how much money I saved by having you guys help me out?

    Sincere Thanks Again
    Brent
     
  22. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Glad you got it sorted out (and it's lucky you have multiple fan speed switches to swap around -- no such luxury on a TR). When Malcolm said "9 out of 10 times it's the transistor", I thought to myself "how about 99 out of 100 times". Seriously, the way they designed that system the power transistor is almost bound to fail because when you think you're being a little easier on things by running at 3/4 max fan speed that actually really cooks the transistor -- it's much better life-wise for the transistor to run the fan at full speed (so the large fan motor current goes thru the relay rather than thru the transistor) when going above ~1/2 speed (but this seems to go against our collective conditioning when presented with an analog control knob ;)).
     
  23. Ferrari_tech

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    Brent,

    Well done and I'm glad that it's sorted - 100 degrees, you lucky thing, it's raining and 65 degrees here in the UK
     
  24. DGS

    DGS Three Time F1 World Champ
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    When the thermostat on my '88 328 failed, I looked it up on the web. It was a G.E. Industrial part, one of the 3ART-series (http://www.geindustrial.com/cwc/products?pnlid=4&famid=1&catid=192&id=refrig&lang=en_US).

    I don't recall which one, offhand. The whole series is similar, so you should be able to order one to fit. The one in the car didn't have an "off" position, which I wanted to add, as I like to shut off the compressor to warm up the evaporator before parking (so it doesn't ice up while sitting with the fans off).

    Note the application: "Vending Machines" -- it came from a Coke machine? ;)

    But it worked fine until it failed, and fit better than the replacement from Ferrari. I don't know if it was the original. Anyone else looked at the markings on their thermostat?

    The GE part should be available from any refrigeration supply house. (Or click "where to buy" on GE's page.)
     

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