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. https://cimg4.ibsrv.net/gimg/rennlis...608ad4bf0f.jpg |
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 |
Thank you. Good to know I'm not the only insomniac.lol..
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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 |
From Tore's website:
https://www.bergvillfx.com/porschehvac2 Fresh air intake screen is shown in this image taken from the article above: https://www.bergvillfx.com/skin/fron...vooverview.JPG This from Tore's site may also be helpful: https://www.bergvillfx.com/porschehvac1 |
Thanks everyone. I will work on the repair as soon as it gets a little warmer in our community garage.
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Originally Posted by TMc993
(Post 15485487)
From Tore's website:
https://www.bergvillfx.com/porschehvac2 Fresh air intake screen is shown in this image taken from the article above: https://www.bergvillfx.com/skin/fron...vooverview.JPG This from Tore's site may also be helpful: https://www.bergvillfx.com/porschehvac1 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. |
Originally Posted by pp000830
(Post 15485155)
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 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. Cheers, Tore Tore |
Thank you Tore! What is an OBD Device?
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On-Board-Diagnostic, google it and you'll find.
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 Cheers, Tore |
An earlier contributor wrote that I will need a #20 TORX tool?
Are there any special tools needed to remove the servo motor(s)? Thanks again. |
Yes, if it can be actuated at ignition on.
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. http://www.durametric.com/buyus.aspx |
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