80-83 HVAC Service With Wiring Diagram
02-09-2019, 08:17 PM
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80-83 HVAC Service With Wiring Diagram
I recently decided to tackle my non-functioning HVAC system and wanted to post the information I found in hopes it helps anyone else with similar problems. Mine is an 1980 with the automatic climate control. After testing and servicing the vacuum actuators and vacuum pods according to the factory service manual, I found that my automatic climate control would not function. After testing my stepping motor and temp sensor circuit according to the factory service manual, I narrowed the problem down to my exterior temp sensor(front left wheel well). It turned out that the sensor was fine, but that where the wires attach to the prongs on the car side of the connector had become corroded. I simply cut the two wires and, with the help of some WD40 and a screw driver, pushed the two prongs out the front of the connector(Image #1).
I then fed the wires through the back, attached new prongs from Microcenter, and pulled them back in to the connector. After this I found my my automatic climate control still would not function.
Mark Anderson from 928 International proved very helpful in confirming the function of the Control Head Unit, so I moved on to the wiring as a potential problem. This is when I started to find problems. Firstly, it became very clear to me that someone had rearranged and spliced wires. Secondly, I struggled to find a proper wiring diagram for the 80-83 model years. All the factory service manuals I found only had 'Current Flow' diagrams for 80-83, and only started showing detailed wiring diagrams for the HVAC system at model year 84 and onward. The 84 and onward models are wired differently, so the wiring diagram wasn't of much help. I eventually found free access to a Porsche Service Information Book for the 82 Model year. I think Porsche sent these out to show how to work with the year-by-year changes and updates without having to go through the trouble of updating the actual Service Manual. Google Search "Service Information 928 model 82" and open the first link. The HVAC Wire Diagram is on page 52. Using this diagram, I was able to make sure every wire was correctly routed. Afterwards, my climate control worked like a charm, and passed all the tests from the Factory Service Manual.
I went ahead and color coded all the wires involved with the automatic climate control(Image #2). I also attached an example of a wire I needed to correct. The image is from after I re-soldered the wire and used heat shrink. Before, it was a 3-way splice left completely uninsulated. My best guess is that when the exterior temp sensor connection became corroded, someone tried to bypass things using an 84 and later diagram. I don't know. I know some owners may have a copy of the Service Information Book, but for those of us that would rather not spend $100 plus on one, now you know where to find one.
If anyone has any questions or needs help with a similar situation, please don't hesitate to ask.
I then fed the wires through the back, attached new prongs from Microcenter, and pulled them back in to the connector. After this I found my my automatic climate control still would not function.
Mark Anderson from 928 International proved very helpful in confirming the function of the Control Head Unit, so I moved on to the wiring as a potential problem. This is when I started to find problems. Firstly, it became very clear to me that someone had rearranged and spliced wires. Secondly, I struggled to find a proper wiring diagram for the 80-83 model years. All the factory service manuals I found only had 'Current Flow' diagrams for 80-83, and only started showing detailed wiring diagrams for the HVAC system at model year 84 and onward. The 84 and onward models are wired differently, so the wiring diagram wasn't of much help. I eventually found free access to a Porsche Service Information Book for the 82 Model year. I think Porsche sent these out to show how to work with the year-by-year changes and updates without having to go through the trouble of updating the actual Service Manual. Google Search "Service Information 928 model 82" and open the first link. The HVAC Wire Diagram is on page 52. Using this diagram, I was able to make sure every wire was correctly routed. Afterwards, my climate control worked like a charm, and passed all the tests from the Factory Service Manual.
I went ahead and color coded all the wires involved with the automatic climate control(Image #2). I also attached an example of a wire I needed to correct. The image is from after I re-soldered the wire and used heat shrink. Before, it was a 3-way splice left completely uninsulated. My best guess is that when the exterior temp sensor connection became corroded, someone tried to bypass things using an 84 and later diagram. I don't know. I know some owners may have a copy of the Service Information Book, but for those of us that would rather not spend $100 plus on one, now you know where to find one.
If anyone has any questions or needs help with a similar situation, please don't hesitate to ask.
