POTENTIOMETER?

Hi Greg:

I'm going out on a limb a little here as I have no experience with the 't'.

I suspect that the potentiometer can't be ordered separately -- I think you may have to order the potentiometer along with its associated circuit board. As a workaround, if the pot is bad, you can probably find an equivalent part from any electronic parts supplier.

See if it has any markings on it, if it does, I can try to decipher them. Also, the older cars have a pot with a switch, these are available too from electronics suppliers if yours is that type.

If you have an multimeter, you can measure the resistance of the pot. It should have three terminals, you should be able to measure a fixed resistance across two of them (that gives the value of the pot) and the third terminal should show a varying resistance relative to either of the others as the shaft is rotated. In fact, if you are able to measure all of these things, the pot may not be bad... time to maybe look at the board it's connected to.

What is the problem you are having? Mechanical fault with the potentiometer itself?

Charles

ps I'm pleased to see that it looks like they replaced the old rheostat for the dash lights with what looks like a potentiometer in the 't'. Mine has a faulty rheostat which I will be replacing with a nice military grade pot controlling a linear voltage regulator... all rated way beyond requirements, I only want to replace it once.

pps If the problem is not the usual fried power transistor, there was a discussion of the board associated with the fan speed control here: http://www.ferrarichat.com/forum/mondial/233550-heater-fan-control-knob-problem-mondial.html

 

The Blower control knob (dimmer switch) unit is in the middle, but this one is for a 3.2 AC control unit (#61078700), prob will work for a T as well but you need the blower unit (#61112300) Speed control (dimmer switch) unit.

Ferrari Potentiometer A C Temperature Switch Testarossa 512TR 512M 3 2 61078700 | eBay
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Ricambi shows:

137983 [137983 POTENTIOMETER]

No. 4 on Mondial T

or

61078700 [61078700 POTENTIOMETER]

No. 39 on Mondial QV

I may not understand your question, but this is what I found.

Jerry
DRG

 

I have a "T" too.
I suggest you search Fchat for "Mondial fan control" or "TR power transistor" There are many discussions to be researched.
My problem, and I believe it is a common problem, is the power transistor that controls the voltage to the fan on any speed other than full on or off.
The temperature is controlled by a simple potentiometer but the fan speed control is actually a small circuit packaged inside a small plastic box. In the 3.2, 3.0 and possibly the 8 (all Mondials) the power transistor is mounted near/in the airflow of the center vent for cooling. In the "T" variant it is inside the plastic box in the center console and is somewhat difficult to replace without removing the potentiometer that is mounted directly above and is soldered to the circuit board.
There are several alternate transistors the can replace the original, but one must be careful to not over spec the amperage capacity as the linearity of the circuit will be affected.
All of these transistors are cheap (under $10). I will be trying several types to determine the best solution.
The original, according to the info I found on Fchat is a 2N3055, 10 Amp.
There are replacements @20 Amps (2N3772), 25 Amps (2N5886), 30 Amps (2N5301) and 50 Amps (2N5686).
I think the main problem is heat. That poor transistor is cooking itself in a small sealed box with no chance of air flow to dissipate the heat. I will be experimenting with extending the circuit somewhere into the cabin (hidden of course) to help alleviate the main issue.
I have just started this process so I can't give you an solid answer or solution...yet.
I will be targeting the 20 Amp and 25 Amp transistor as replacements.
My car will go in for a major within the next month and I plan to fix the fan speed control circuit while it is in for the major. Hopefully after the car is back, the circuit will plug in and work!

 

Strange... this part cross-references to all of these cars but the t is not listed. Perhaps it's the same?
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I'm having the major on my "T" done at Auto Elite (independent) in Tenafly New Jersey. Vinny has been working on this car since 1993 when the car was owned by the original owner. I am the third owner. The second owner also had the car serviced there as well.
The base price for the cam-belt replacement service is under $5000 including parts. I am having a few other items taken care of as well so it will be more in the end.
Some of the other items I want addressed are: replacement of the all the fuel system rubber parts. Plugs and wires. Valve adjustment. Front shock absorber repairs/rebuilds. Steering rack rebuild. Suspension bushings replacement as needed. Coolant hoses.
Of course there will be other things that will be found during the engine out.
I'm sure I won't get the car out of the garage for less than $8500, and there will be much more to do in the years ahead.
If you want to run with the big dogs....it costs.
I will be working on the car myself as well: The fan speed control, replacement of most of the switches in the cockpit as well as the clock. Removing the old alarm system, replacing the sound system head end and amps/crossover. Next will be the carpets. Thinking of changing them from tan to black.
Also the door window guides. While I'm in the doors I may put the window accelerators in.
The list goes on and on. Thinking of the Gold kit from Dave Helms. Over time it will all be addressed.

I have been over to Auto Elite a few times last year for an oil change, etc. They found a damaged rear shock and replaced it as well as addressing a leaky cam seal. They were great. Fast and a good price. I stopped by last Saturday after C&C in Chatham NJ and joined a bunch of really nice people for some lunch. A real generous group. What a meal! And so many great cars in the shop. Two 246 GTS Dinos, 348 TS, 355 Spyder, 360 Spyder, 308 GTS, Fiat Dino, an older Lancia and a older Alfa, both that I didn't have a clue about, 512 BBI, and too many more to list here.

I'm sold on Vinny and his mechanics.

DavidJ

 

Could it be the power transistor?