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Heat and Velocity Temperature Different Driver/Passenger Side.
I took my car out for a two (2) hour ride last night. The outside temperature was about 28 degrees. Once the car reaches normal operating temperature and is idling or driven at slow speeds, the heater works normally. I noticed when I drive my car at highway speeds, the car does not deliver heated temperature to any of the vents. When I returned home and the car was idling, the temperature returned to heated air to all of the cars vents. It seems the faster I go, the less heat in the cabin. And the slower I go, the greater the heat in the cabin. I hope this is something simple.
I am attaching a photograph of the temperature gauge that remains constant at highway or slow speeds, including idling, once the car reaches normal operating temperature.
Appreciate your help. I hope it's something simple.
Last edited by Twilightblue28A; 03-02-2019 at 08:17 AM.
Likely the fresh air servo has failed in the open position.
Tape over the fresh air intake in the cowl and go for a similar drive, see if the car delivers heat.
Gordo
Where in the car is the fresh air servo flap that is suspected of failing open, where do I tape, what type of tape should I use, and finally, will this affect the air conditioning temperature in the cabin in warm weather?
I know more about Oldsmobile 442's than Porsche.
Thank you for your help.
Yes I agree with the other posters. It is likely the fresh air servo located in the frunk in the center behind the dash. Just remove the plastic shroud on the cowl in the frunk and it is on top in the center. It can be tested by turning on the ignition and moving the levers on the climate control unit and looking to see if its arm moves. Also one of the other Servos can be contributing to your issue. Nice thing is that if you run the OBDC codes in Durametric it will tell you which one(s) have failed. Servo rebuild kits are available from Partisan in Germany, they will also rebuid them for you if you prefer.
Andy
The arm can be made to present in two positions one making it easier to detach the vent plunger from the arm and the other making it easier to remove the servo from its frame. If it does not move when turning the ignition on then see the following: https://rennlist.com/forums/993-forum/838379-993-hvac-servo-removal.html
Andy
Can I remove the fresh air servo by removing the fresh air servo from the group of servo's? Are there rods attached? Does the fresh air servo motor slide out horizontally or vertically? Also, there are terms being used to which I'm not familiar and to which I don't have a close up photograph to identify the parts/rods to remove as a pre-condition to removing the fresh air servo.
The photograph identifies the fresh air servo as number 2, but no further identification of parts, rods, etc are pictured for identification.
I will need step by step instructions please.
Further, the reason that we are focusing on the fresh air servo is because at slow speeds, the cabin is heated, and at high speeds, no heat is delivered to the cabin.
Also, PP00830 made reference to a device that can identify the operation of all of the servo motors. What is this tester called and where do I get one?
I can rebuild an Oldsmobile 442's engine, transmission, and rear differential, and restore the entire car, but I a need to get familiar with this car.
Thank you.
Yes I agree with the other posters. It is likely the fresh air servo located in the frunk in the center behind the dash. Just remove the plastic shroud on the cowl in the frunk and it is on top in the center. It can be tested by turning on the ignition and moving the levers on the climate control unit and looking to see if its arm moves. Also one of the other Servos can be contributing to your issue. Nice thing is that if you run the OBDC codes in Durametric it will tell you which one(s) have failed. Servo rebuild kits are available from Partisan in Germany, they will also rebuid them for you if you prefer.
Andy
Andy,
What is/are OBDC codes and what is Durametric? Also, if the arm moves, what is the next step?
Thanks!!
I would suggest to test all servos and fans, as well as the resirculation flap.
An OBD diagnostic device is helpful in diagnosing these issues, but the best test method is done manually by inspecting servo arm movement and fan operation. My DIY page linked in the posts above describe a test procedure that is done in ten minutes.
Removing the fresh air servo is done by removing the two screws on top of the servo housing. Depress the pushrod out of the nylon bushing on the servo arm. If the arm has stopped in a position that makes it impossible to remove from the metal bracket, use a small screwdriver or other tool to press out the metal servo arm from the servo housing.
Refitting the pushrod into the nylon bushing when reinstalling a new servo is a bit tricky. I use two screwdrivers to press up the rod and snap it into place. The bushing must also be rotated correctly to fit the rod properly
PARTisan Autoteile has servo a refurb service, as well as selling kits instead of buying the very expensive spare part from Porsche.
An off-the-shelf OBD reader/scanner (wireless or not) will at best be able to communicate with the Motronic engine management system in the 964/993. As far as I know, there's only a handful of systems that can do all the OBD-connected things in our cars. (Motronic, ABS, SRS airbag, alarm and climate control)
*Original Porsche OBD tools as the Bosch Porsche "hammer" (KTS 301) or later systems as PST2 or PIWIS v1 or v2 (not v3!)
*Freeware Rennlist Scantool Windows software (a serial port adapter as our T-OBD needed, also described in numerous threads on this forum)
*Durametric Windows software with a proper serial cable
*Jenniskens OBD UDT/PDT999 diagnostic tool
Can I remove the fresh air servo by removing the fresh air servo from the group of servo's?
Yes, if it can be actuated at ignition on.
I will need step by step instructions please, call me to discuss. There are two methods depending on if your fresh air servo motor is working when the ignition is turned on.
Further, the reason that we are focusing on the fresh air servo is because at slow speeds, the cabin is heated, and at high speeds, no heat is delivered to the cabin. Yes, with the fresh air vent open the available warm air from the engine compartment is fan driven at a constant rate while the cold air supply rate is dependent on the speed of the air rushing into the cowl opening.
Also, PP00830 made reference to a device that can identify the operation of all of the servo motors. What is this tester called and where do I get one?
See Enthusiast kit for $287, buy the cable and download the MS Windows software, will read all 993 codes, has some potential bugs but works in most cases just fine. You will need a laptop to run it on when connected to your car.
12-09-2018, 03:14 AM
Heat and Velocity Temperature Different Driver/Passenger Side.
