1987 328 A/C question

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.

 

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.

 

[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

 

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

 

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.

 

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.

 

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.

 

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.

 

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 ).

 

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

 

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.)