I need some advice on my 2000 Series II. I have begin having an issue with the above dash portion lighting up when the headlights are turned on all other interior lights still work. When the dash light is out, also the rear marker light and the licence plate light are out. After driving sometimes they all will starting working again.
I have check fuses and they seem to be fine. Anyone out there had this issue.

Ken

 

If its intermitten sounds like chewed up wiring somewhere... very very common for these damned things haha. id remove the cover, unplug all the harnesses and reseat them, while checking the wires, they bend pretty tightly back there from what i remember, and when i opened mine i found broken glass, pieces of sheet metal fraying and tons of sand, dust and a few pennies haha. if not there, check the connections to the computers under the pass. side kickpanels, they might be loose or rubbed through under there. electrical gremlins are a pain in the *** sometimes, I get lucky spreading the wires by hand, shacking them a good bit until things work, then taping the wires where they lay haha

 

Check fuse #10 in the underdash fuse panel, that supplies power to all of those, one of the first things I do in situations like this is replace the fuse, I've seen the wire in the fuse be broken and as you drive it the broken wire wiggles around and by chance touches the other broken element and it starts working until it cools down and breaks contact again. Some other things to look at to narrow it down to that fuse is: Illumination in the rear wiper, rear washer, and the cruise on/off switch. Do all of those go out when the dash lights do? They are on that same circuit as well.

 

Did you say #10 supplies power, then what does #11 do.
I checked cruise control light and it works even when dash illimition is not.
Thx Ken

 

I wasn't referring to the light that goes on when you push the cruise button, but the illumination of the symbol on the switch when you turn on the lights. (its supposed to light up, maybe yours never has and you think it wasn't supposed to) Not sure about #11, I found what 10 controls by going through the various circuits in RAVE. It's sometimes hard to find common faults in a current flow diagram (which is what the RAVE diagram is) because it only shows the circuit for a particular system. To get commonality you have to look at one circuit, remember (or write down) the fused source for that circuit (along with various header points), then look at the other circuit and see if there is a common point between the two. You can blame Porsche for this "current flow" idea for wiring diagrams, they thought it up in '74 and a bunch of manufacturers jumped on the bandwagon over the years, I think the engineers like it, but it drove me nuts. Porsche finally saw the error of their ways in the 90's and went back to the old wiring diagrams that show everything on one circuit. Of course that all goes out the window with multiplexing systems that everyone uses now. That's a whole different story, maybe that's why I'm glad I retired.

Edit: I just looked at the diagram again, I gave you wrong information, it should be fuse 11, I must be getting senile, or maybe I was looking at the 10 amp fuse legend and somehow transformed that into fuse 10, sorry. good catch. I'm not saying it's a fuse, it's just a place to start. The difficult part about intermittent electrical problems is that many times you don't know immediately if you've fixed it or it decided to work for a while.

 

I will check the cruise light and get bck to you. Thanls again.

Ken

 

One good piece of advice I got at the advanced electrical diagnosis class that I took at Jaguar was: "Before you start pulling things apart, don't get tunnel vision about that particular problem. Look at all the various features of the car and see what is and isn't working, then look at the wiring diagrams for commonality". This advice has helped me many times over the years. For example, in this particular situation, if the switches in the binnacle don't light up when you turn the lights on it may be a supply problem, but, if they do light up, then you've eliminated at least the common supply idea. Another thing to look at is if it has an aftermarket radio or gauges, many times the installer taps into a handy "hot when the lights are on" wire to operate the auto dim function. If they used the Scotch type wire taps they can break the wire to part of the circuit. Just a thought. Keep at it, electrical stuff can be frustrating but it's still just a machine designed by a human so a human can fix it.