512TR Airco problem

I believe those are two separate problems:

For the "My knob for volume of air (25) will only give full cooling", your 512TR uses the same blower motor current control architecture as a TR so the problem is either the power transistor (not so expensive and most likely IMO), #1 here:

http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=1057

or the speed control ECU with the knob (expensive and less likely IMO)

If you do a search on "TR power transistor AC" it should get you a lot of threads where others have given a PN for an equivalent T03 transistor (you can reuse the heatsink) -- or look in the TR cross-reference thread.

For the other problem, see if you can see the horizontal air butterfly valves on the side of the AC unit -- one is visible in that SPC figure to the right of the "34, 35, 34" labels. The bar LED represents the motion of the butterfly plate. Don't have advice on how to fix, but determining whether:

1) the LH air valve is stuck fully open and the LED is giving a true indication, or

2) the LH air valve does move properly when using the switch, but the LH LED gives a false indication

might give a clue about where the trouble lies. IIRC, 348s have a lot of trouble with the motor/mechanism for the air valve breaking and your 512TR might use similar components.

PS To prevent blowing up the power transistor in the future, it is best to operate only from 0 to 1/2 speed or full speed -- operating in the 3/4~7/8 speed range really toasts the power transistor (and this goes against human nature where we always "back it off a little from max" when we're given a knob to turn ).

 

At the risk of getting too personal, your knobs look "sticky"

 

The power transistor is used to control the amount of current (and, therefore, the speed) of the blower fan motor at any setting below maximum. When you turn the knob to maximum, a relay closes and supplies the (full) current to the blower motor bypassing the power transistor (this is why when the power transistor fails, max speed still works, but not any lower speeds). See post #2 in this thread:

http://www.ferrarichat.com/forum/showthread.php?t=233550

This type of current control is referred to as "common emitter" -- if you do an internet search on that term you should get more explanation/description.

 

If it's in the stock locatiion, I believe it willl be in the same place as on a TR -- inside the vent area of the main cabin air outlet (the idea is/was using the AC air to help cool the transistor -- but it doesn't really work well enough ). I don't think that you'll have to disassemble the entire dash (as shown in this TR particular example), but you will need to remove center vent assembly to get access:
Image Unavailable, Please Login

The other thing to check/compare is if the collector, base, and emitter terminals are in the same places, or not, on the old and new transistors. The overall package is obviously compatible, but not sure if the terminal location are always the same.

 

Glad to hear that you got it working again (and at a reasonable price). I can't fault the designers, as mounting the power transistor in the outlet airstream is about the best you can do for cooling it. I doubt that your finned heatsink in a convection situation (no forced airflow) will work as well as the stock arrangement, but if you only use very low speeds, or full speed, it might be OK (and if it blows up again your cost to fix will be low). The stock mounting location PLUS your finned heatsink would be best .

This is harder. If you've confirmed that the flap is stuck in the wide open position, that's a good sign for the LED display (i.e., it is correctly describing the flap's position). Don't know if you can get to the connections, but the next step IMO would be to measure the voltage at the flap motor itself when commanding it to move to determine if: 1) the electrics are working, but something is wrong with the motor/mechanism, or 2) if the electrics aren't working. The only other thing I can think of is to give the flap a little gentle mechanical help to close while commanding the motor to close it -- if you are uber-lucky it might just be stuck. Sorry I can't be more specific, but you are in unchartered waters -- please let us know how it works out.

 

Mondial has the same switch and transistor configuration. My ventilator also worked only at max. speed. Find out it whas a blown fuse on the switch. Transistor is placed in the same place on the blower outlet.

Guido

 

The early fan speed control ECUs (circa 1988 and before) had a 1A fuse that would also disable the variable speed operation if blown -- later units, like yours (thankfully ), don't have it.

 

http://www.eurospares.co.uk/userImages/012/Large/012_122.gif

number 40 and 41.....

Guido

 

Sorry to resurrect an old thread, but wonder if I could get your opinion on a related topic.
The blower fan on my car doesn't switch off - with the fan control dial turned all the way to click off and the main A/C Stop button pressed the fan still runs at a fairly high speed all the time (with ignition on).

Reading this thread makes me think it could be the power transistor which troubled Melvok - does this sound like suitable symptoms?

 

So I opened up the center console and had a look at the blower control. Underneath the fan speed control is this:

Note I don't see any fuse on the control as in other posts. It has 4 wires going to this connector:


I disconnected the connector and it made no difference - as soon as the key is turned to position 2 the fan comes on (I'd say at around 80% of maximum).

Other symptoms/findings:
I tried swapping the air con relay and double checked the fuses - no difference.
If I switch on the air con to one of the 3 modes, the fan speed control can increase/decrease the fan speed slightly at the top end (between 80% and maximum) - if I hit the stop button it goes back down to the 80% level regardless of the setting on the fan speed control.

Any thoughts on what to try next?

 

I am having this same problem along with a seperate issue with the AC blower I will post seperately.

Does anyone have any particular heat sinks that they can recommend to use to mount the transister? I plan on mounting it in a more convenient location.

 

To add a bit more information to my situation. The fault developed while at the dealers for a cambelt change (so engine out, aircon regassed etc) - is there anything in the electrics which could have been reconnected wrongly? I'm not sure how the blower control would relate to the compressor etc in the engine bay, but a shot in the dark here....