mgianzero

So I pulled the fresh air flap servo motor from my 993 as it stopped working (does not move) and throws a code 24 - "fresh air flap motor" with my PST-2. The potentiometer tracks and whiskers do not appear to be noticeably burned, nor to any solder joints appear to be broken. (See pic)

My question is, before I spent $300 on a new unit, how can I test and possibly repair my servo motor? Which pins (#1 thru #5) do I connect to a 12V source to test this unit? Which cold solder joints can be the culprits and how do I test for their continuity?

Marc G.

ToreB

The electric motor could be faulty, there has been reports of motor wear and short circuit.
Below is a schematic of the servo, you could connect 12V to terminal 4 and 5 to test the motor and limit switch, and a ohmmeter to terminal 1 and 2 to test the pot.
The Climate Control Unit servo output could be shot, I would guess the easiest way to test this is to connect the servo to another servo output and test it in-car. A CCU failure is by the way fully repairable.
Cheers,
Tore

Mike J

Gotta love this place - go for it Marc!

Cheers,

Mike

mgianzero

Okay guys. It helps to have a PST-2 to diagnose these things. (I set up a clone one from a IBM Thinkpad this year. Not too difficult to do.)

Here's what I did ...

Like Tore says posts #4 and #5 are the voltage sources to drive this servo. I noticed (with multimeter) that they switch between +12V and -12V, depending on the direction desired. Also, the potentiometer is read by the system so that it knows the motors exact position at all times. I even tried to fool the system by disconnecting and reconnecting the motor after I manually moved the arm (by taking box apart temporarily. Don't worry, I didn't strip any gears.)

My servo motor appears to be dead, dead, dead. And, once again, no significant burn marks on the PCB. So I took the motor out of the defroster servo and put it in the fresh-air servo and it works perfectly! When I put the "bad" motor into the defroster servo, nothing. So I guess my electric motor is bad.

I know some folks had some bad servos due to a shorted out board. Anyone willing to send me the supposed good motor to replace mine? What Porsche wants for a new servo is quite a bit.

Marc G.

mcipseric

Please PM me on how you did this. :-)

Thanks!

mgianzero

PM sent.

hchc

Can you PM me as well? Thx!

Blue TTop

I'd like to request a PM as well. TIA

XR4Tim

I'd also like that info if you don't mind.

Stealth 993

I went through this on my C4. I propped the servo up under the hood so you can see it from the drivers seat and plugged it in. The started the car, and moved the HVAC dial to activate the servo. They move slowly.

mojorizing

Did you locate a spare motor? I might have one if you need me to check.....

mgianzero

Actually, what I did was I swapped the motor from my fresh-air servo with the motor from one of the footwell servos. Now it works perfectly! Then I went ahead and installed the "supposed" bad motor in the footwell servo and it worked too! So I don't know if there was a dead spot in the motor or what. Now it seems to work fine. Any one got ideas as to why it would stop working with one servo, but works great in the other?

I purchased another used servo as a backup, just in case. So I think I've fixed the problem, at least temporarily.



Marc G.