911sc electrical questions/issues

[Roby466]

Hi,
I'm working a few electrical issues on my 1981 911sc and I have some things that remain unknown...
Here is the story, it's a bit long. When I got the car, the fog lights worked but they could be turned on whenever the ignition was on regardless if the low beams were on or not. Also, if the headlights were off, turning the fog lights on would turn on the headlights as well. Also, the rear window defogger was not working.
The fog lights issue is sorted out. The power to the rear window defrost was connected to the fog lights switch feeding back into the headlight circuit when the switch was turned on (probably drawing way too much amps and was a possible hazard). Here are the issues:
-The defogger now works but I have a questions. There are 3 wires that feed out of the switch: a black, a grey and a black/white.
The black one feeds to the rear defrost relay and was connected on a double connector with the grey one that feeds to the heated mirrors. The black/white one also feeds to the rear defrost relay.
Here is the question. The black wire will heat-up the center of the window and the black/white one heats up the top and bottom of the window. How is the system supposed to operate? Is it first position: center part and mirrors (as they were already on a double connector) and second position everything together or would that be too much current?
Anybody who could do a quick field test on his car would help greatly. Just telling me what happens at what position of the switch.
-Also, I found this wire (first picture): a white wire with a green line on it. It comes out of the same loom as the two rear defroster wires but is not connected to anything. It comes out of the loom just behind the defrost switch like the other 2. Any idea what it could be?
-And lastly, the wire in the second picture was found taped off laying on the engine. It has a red/white and a brown wire going into the connector.
I know that this is a long text and a lot of questions but as they are all related to the same job, I put them all in the same post... I tried to find what the wires were by studying the Bentley diagrams but could not find the andwer.
Thanks for any help
David

[kerthunk]

The 2nd pic with the red/white & brown wires looks like the electrical connection for the thermo valve. I believe that the thermo valve should be connected to the bracket that is holding the heater blower fan. It is a little disk shaped thing with 2 vacuum tubes going into one side of it. At the opposite side of the disk, there are a couple of prongs that your connector should hook up to. I believe that it is just a heating circuit, so it shouldn't matter which way the connector fits on it.

Also, wasn't there an issue with mounting those MSD blaster coils upside down?

[Roby466]

I remember reading about mounting the MSD blaster upside down but this being the High Vibration coil, I think that it is supposed to be ok upside down... I will look for that thermo valve... cannot remember if it is there.
Anybody else knows something about these wires or the operation of the defogger/defrost?
Thanks a lot. I would hate to put the air/heat unit back on and then realize that something has to be plugged an other way and have to take it all apart again.
David

[Roby466]

Anybody has any idea about the wires?
Any idea how the rear window defogger is supposed to operate?
Thanks

[Roby466]

Ok,
I found what the white/green wire was behind the switches, it is the wire for the rear fog light. The wires going to the fog light itself (if it was installed) are taped up in the back of the rear driver side fender.
I still have to find exactly what the other wire is on the engine (second picture)
David

[kerthunk]

Originally Posted by Roby466

I still have to find exactly what the other wire is on the engine (second picture)

I'm still pretty confident that it is the wire to the thermo valve. It is connected to the same bracket as the blower fan.

[Roby466]

Is it possible that this thermo valve was removed from my car? I found the wire laying on the cooling housing and the plug was taped up. I looked quickly in there and did not find anything attached to my heater fan bracket. What does the thermo valve do?
Thanks again and thank you for the picture, it will give me a better idea to what I'm looking for. I am at work until tomorrow morning. I will look again in the morning.
David

[boyt911sc]

David,

Could you post pictures of the WUR and the motor blower area? Thanks.

Tony

[Roby466]

Absolutely, I will in the morning when I get back home

[kerthunk]

The thermo valve can be an optional item. It blocks off the vacuum pressure between the throttle body and the WUR for 30 seconds or so (on a cold engine) to provide warmup enrichment.

[Roby466]

Thanks for the help. The pictures are not very good... my camera is having problems... There is definitely nothing on the vacuum line between the WUR and the throttle body, so I guess that I don't have the thermo valve. Should I install one? I don't really have major starting issues yet.

[Roby466]

Reading in Bentley, it says that in 81, a cold enrichment system was added. It cycled the frequency valve differently until the engine warmed up, that may have been when the thermo valve was removed... not too sure though

[boyt911sc]

Originally Posted by Roby466

Reading in Bentley, it says that in 81, a cold enrichment system was added. It cycled the frequency valve differently until the engine warmed up, that may have been when the thermo valve was removed... not too sure though

Roby,

Your '81SC is not equipped with thermo-time valve. So don't worry about it. Secondly, the FV (frequency valve) has nothing to do with the engine warm-up operation. Go drive and enjoy your car!!!!

Tony

[Roby466]

Thanks for the help... I will just tape this wire back and leave it there I guess.
David

[Vereeken]

Guys,

Quickly high-jacking this thread, but first allow me to answer the basic question.

Yes the wires pointed at are for the Thermo valve. You do not have one because your WUR is not equipped to accept the vacuum hose going from the thermo valve to the WUR (left side, lower and point out to left). So either you never had one or someone replaced the WUR with another model.

The thermo valve opens at 45degrees celcius engine heat or after 45 seconds of current running to it after engine start, when it opens it allows vacuum to go through to the WUR and leans out the mixture.

In my experience the thermo valve is a must have in a colder climate.

And now to my question. My thermo valve is caput. It is open ALL the time so at start up it already leans out my mixture, I do not want that. But I want a thermo valve. Problem is I can not locate it on Pelican. Does it carry another name? Does anyone have a link to the Bosh or Pierburg part number?

Also for the benefit of others a thermo valve that is always open can cause the following running issues:
Because of the valve being always open it leans out straight after start. So as a result you tend to increase the fuel delivery by increasing fuel on the fuel distributor. That solves that problem; But after warm-up you are now effectively running too rich, so you tend to back off the fuel delivery, next time you start on a cold engine you are now too lean and the engine will stumble and your story can start all over again.
You can check your thermo valve by unplugging the vacuum hose from valve to wur. If it sucks air on a stone cold engine the valve is caput. It should only be allowed to suck air after 45 seconds.

Now if someone has a link to the part number or any reference...I would be ever so greatful.

Michel

[kerthunk]

The porsche part number is 911-606-106-01. Here is a link to the part on Pelican:

Pelican Parts - Thermo Valve

Yeah, I noticed that his WUR didn't have the vacuum port for the thermo valve in the pics he posted. Seems odd that Porsche would stop using the part but still leave the connection on the engine harness. Of course, I have seen a few "odd things" with these cars.

[Vereeken]

Found it thanks.

It is apparently not a Bosch part but a Pierburg part. I went to the shop and they called Pierburg. It is no longer available. Bummer.

Off to the breaker yard. Mercedes, Porsche Citroen Saab all carried the same Thermo Valve or Termo Ventiel as in the German description.

Michel

[kiwiokie]

My '83SC has the same disconnected 2 pin plug and no thermovalve.

[RSM-M491]

I needed a new Hazard switch, which I have, but can not get it to plug back in, the receptacle moves every time I try to put it in place. Any tips on this?


Thanks!

Rod

[Roby466]

I think you can get to the hazard switch from under the dash, just get under there and hold the back in and it should plug in...