02-09-2014, 03:57 PM
I queried earlier that my heater was blowing hot without the switch activated. I had experienced the clip failure on the threaded rod positioned behind a removable cover to the right of the driver's knee some years ago. I had reattached the failed clip it with fine wire. This time I as I opened the compartment the small u-shaped sheet metal clip--I had apparently replaced it on the original fix--fell out. I reattached the threaded rod with fine wire. Upon driving the car, the heater came on and remained so until I reached my destination. When I restarted and drove the car home, the heater remained off. I hadn't touched the heater switch, which remained off. Great! Next time I drove the car exactly the same thing happened; the heater was on initially, off when the car was restarted.
Next I looked at the heater control valve, which I had replaced with a stock unit some time earlier. With the engine running, it did not appear to respond (close) with the switch off. At one point I did see it move as I turned on the heater switch and rushed around to. look at the valve. I next bought the suggested part-metal Audi heater control valve and installed it yesterday. As the vacuum hose teat on the Audi controls diaphragm was smaller that the Porsche version, I drilled out the interior of that piece on an old control valve, cut it off, and slid it over the metal teat on the Audi part. No problem. Originally thinking I might have to replace the entire vacuum hose to make it reach the Audi part, which positions differently than the original, I had unhooked the original hose where it runs below the front of the firewall behind the engine. It connects by a rubber sleeve to a greenish hose that dives down to the netherland behind the right side of the back of the engine. Since I found the original hose that I disconnected would reach the Audi valve, I simply reconnected it to the green hose. Incidentally, the newly removed Porsche control valve appears to function correctly.
With everything reassembled, I took the car for a drive with the heater switch off. I got heat. I then checked the function of the Audi control valve. It did not respond to the switch, suggesting the hose had no vacuum. I also viewed the threaded rod connection inside the cab and find it does not respond to the heater switch with the engine running. But there was a new gremlin, the car's idle now runs up and down and the car appears ready to stall at idle but drives OK. There is one other wrinkle. There is an electrical apparatus that mounts between the power steering reservoir and the engine head above the heater control valve. I found that this electrical bit had shed part of its plastic lower extremity exposing three (I think that was the number) small wire connections. I covered those connections with black rubber gasket sealant to seal them against arcing. I have no idea what the electrical bit does and whether I altered it's function. I suspect the heater control switch has failed. Thanks for your patience in wading through all of this.
Next I looked at the heater control valve, which I had replaced with a stock unit some time earlier. With the engine running, it did not appear to respond (close) with the switch off. At one point I did see it move as I turned on the heater switch and rushed around to. look at the valve. I next bought the suggested part-metal Audi heater control valve and installed it yesterday. As the vacuum hose teat on the Audi controls diaphragm was smaller that the Porsche version, I drilled out the interior of that piece on an old control valve, cut it off, and slid it over the metal teat on the Audi part. No problem. Originally thinking I might have to replace the entire vacuum hose to make it reach the Audi part, which positions differently than the original, I had unhooked the original hose where it runs below the front of the firewall behind the engine. It connects by a rubber sleeve to a greenish hose that dives down to the netherland behind the right side of the back of the engine. Since I found the original hose that I disconnected would reach the Audi valve, I simply reconnected it to the green hose. Incidentally, the newly removed Porsche control valve appears to function correctly.
With everything reassembled, I took the car for a drive with the heater switch off. I got heat. I then checked the function of the Audi control valve. It did not respond to the switch, suggesting the hose had no vacuum. I also viewed the threaded rod connection inside the cab and find it does not respond to the heater switch with the engine running. But there was a new gremlin, the car's idle now runs up and down and the car appears ready to stall at idle but drives OK. There is one other wrinkle. There is an electrical apparatus that mounts between the power steering reservoir and the engine head above the heater control valve. I found that this electrical bit had shed part of its plastic lower extremity exposing three (I think that was the number) small wire connections. I covered those connections with black rubber gasket sealant to seal them against arcing. I have no idea what the electrical bit does and whether I altered it's function. I suspect the heater control switch has failed. Thanks for your patience in wading through all of this.
