Using '83 defroster switch in '78 car
 

In a nearby thread, I explain that the '78 dash switches are very different from the '83 dash switches. If I can, I would like to install the '83 switches into my '78 SC. The reason is because the bulb in the '78 switches is located at the rear of the switch, requiring removal of the fresh air blower unit in order to change the bulb. But...I am confused about the wiring. The '83 switch terminals are numbered, as with most Bosch stuff. The terminals on the back of the '78 switch are not numbered.

As you can see, the '78 switch has a green jumper wire from one of its terminals to another. In fact, this switch has only four spade terminals. the '83 switch has six.

The schematic does not show a green jumper wire. The schematic shows only two wires going to the defroster unit, suggesting only one defrost circuit. Untrue. Both the '78 and the '83 cars have two working, functional circuits in the rear glass. Help me understand how I might connect the '83 switch (shown) to the wiring in the car which is currently connected to the '78 switch (also shown).

http://forums.pelicanparts.com/uploa...1549833750.jpg
http://forums.pelicanparts.com/uploa...1549833750.jpg
http://forums.pelicanparts.com/uploa...1549833750.jpg
http://forums.pelicanparts.com/uploa...1549833750.jpg

It would be helpful if I could get answers to these questions:

1. 1978 SC
1a This car has working heated outside mirrors, right?
1b The defroster switch has three positions, right?
1c Those three positions are IN, OUT one click and OUT two clicks, right?
1d Outside mirrors are energized when the defroster switch is out either one or two clicks, right?
1e Out one click defrosts part of the rear glass, right?
1f Out one click defrosts all of the rear glass, right?

2 1983 SC
2a This switch has four positions, right? It clicks out one click, and it also turns to the left one click, right?
2b Out one click defrosts part of the rear glass, right?
2c Out one click and turned one click to the left defrosts the entire rear glass, right?
2d Out one click -OR- one click to the left energizes the outside rear mirrors, right?

Those of you in cold climates might have information about how these switches work. Do tell.

Mission accomplished. I am posting this for reference by other Pelicanheads. I seem to have successfully transplanted these dash switches (rear window defogger and fog light) from an into a '78. Part of the reason I did this is simply because I like the aesthetics of the '83 switch knob icons better than those of the '78. You can see the difference in this other thread, which I had created discussing the differences in bulbs and bulb replacement:

http://forums.pelicanparts.com/porsche-911-technical-forum/1016784-dash-switch-bulb-replacement.html

The other reason is for purposes of future bulb replacement, which is much easier with the '83 switches. Again, this is discussed in the other thread.

There were three problems in doing this transplant. One is that the old switches lack terminal labels. the '78 switches have brown bodies which do not say "31" or "15" or whatever on the switch terminals. Therefore, I had to figure things out using the colors of the wires, which was another problem. I have the Bentley and Haynes manuals. The Haynes manual turned out to be more useful, but the wiring in this '78 does not actually match ANY of the diagrams I have. I had to verify proper switch wiring partly by using a multimeter to ensure the rear window defogger was getting voltage properly from the rear window defogger switch.

Finally, I had to drill out the holes in the dash. the plastic nuts which hold the switches onto the dash, and the switches themselves, are different. The '83 nuts are male and the '78 nuts are female. The holes needed to be bigger in order for the '83 plastic nuts to get through the sheet metal and engage with the switches. Here is a picture of the nuts. This project is doable. If someone else does this, then I hope this thread is useful.

http://forums.pelicanparts.com/uploa...1550437823.jpg