rgs944

One more thing to add, When the passenger tail light wiring is all unhooked, neither the passenger side brake light or the 3rd brake light will work. The driver side brake light is not affected.

rgs944

I moved the drivers tail pod to the passenger side and everything worked fine. So conclusion is that one problem is in the passenger pod. I have been over it with fine tooth comb and can not find the short. Need to keep looking. The other problem I have is with that the drivers pod has two tail lights out. The outer tail light and the tail light on the dual brake/bulb. So that problem must be in the wiring somewhere or on the CE panel. Is it just me or does anyone else think that German cars have the worst electronics of all time. I had a 2000 VW jetta once that was rated by consumer reports as the worst electrical car of that year. After owning one I sure believe it. For God sake there are American cars from the 50's that never ever give you any brake or tail light trouble other than blown bulbs. This is just over engineered junk. Enough ranting, back to wire tracing.

rgs944

Progress made, I am not sure exactly what I did but after I rewired the passenger side light pod I have got rid of my short in that pod. Now the problem I have is tail lights on the drivers side. The brake light works but the tail light in the dual brake/tail bulb does not, nor does the single outer tail light work. The center single tail is the only one that works. The problem is not in the pod as I have tested it on the other side. Next I will look for shorts in the CE panel. I did take the bulb control out and found one area that could be a problem. Cleaned it but it did not make a difference. Can someone tell me of any junctions or panels to look at specifically on the CE panel?

borland

There's nothing fancy about the German engineering here. This is a pretty simple bulb wiring design.

Only one of the S4/GT/GTS tail lamp bulb sockets is a dual filament socket. The rest are single filament. But all sockets have have three wires coming out of the back. That may be confusing to some.

The reason the sockets all have three wires is because the grounds (brown wires) for all sockets are ganged to reduce total wiring lengths. The ground wire originates at the dual filament socket, and then wired to the next bulb socket, and so on, finally terminating at the connector.

So, it you have an interuption of the ground wire at one of the sockets, any bulbs upstream will not function properly. That could be your problem. So, I'd suggest you use a multimeter to trace your grounds from each socket to make sure there is no interuption.

The Napa or Nissan socket (as you call it), provides only one external ground wire, so for my LED tail light wiring mod, I tied the grounds together external to the socket.

rgs944

Thanks Borland, I am not good with electrical at all so I am sure that is a big part of the problem. I do not think I have a ground issue. As you said the grounds all run together. If you start at the dual I have no light, the middle single tail does work and the outer tail does not. Are you saying that there is one single ground that comes to the plug juction on the pod? That is the way I see it but I just want to make sure. If that is the case the ground should be fine as the middle tail is working. Also remember I have switched pods from side to side to eliminate a problem in the pod. I believe I should be looking at the power feeds for the non-working lights from the source to the pod plug. Does that sound right? Thank you for your help.

Landseer

The back of the car has a single shared ground point.

rgs944

Thank you Landseer, I did clean that but I will go over it again to make sure.

Landseer

You might want to sketch the system as you've rewired it, take a photo, and post it.

Know that CE panel power passes through the bulb control unit for tails/markers and stop lights.
Bulb control unit (bulb comparator) is mounted on the passenger package tray, against the right side of the car, tucked away.

Also there are separate fuses to check on the left and right circuits for tails/markers.

I'd be checking for power at the harness plugs prior to the tail lights using a voltmeter.
Might need a helper to stand on brakes.

borland

Yes, if the dual filament bulb is working properly, then it is not likely a ground problem.

Since you interchanged the lamp assemblies and get good results on either side, then you can rule out the car side of the electrical system as causing the problem.

Check the individual power wires from the connector to the bulb socket for continunity using a multimeter. That should isolate the problem to individual socket(s).

rgs944

Thank you guys, I have found the short. It is in the bulb control unit. Remember I thought one spot did look a little funny. I will try cleaning it but I am sure I just need to find a new one. Thanks again for your help. Things are looking up, I also just recieved my new Ford injectors in the mail today.

rgs944

Quick update, the short was not in the bulb control itself but rather the wiring going to the plug. When I was messing with it to defeat the bulb control I must have created the short. I have now unhooked the #7 and #10 pin. Do you think will this will create any problems for me like cruise control?

borland

The plug is on the chassis side. Unless you mean the harness socket on the tail light assembly, that doesn't explain how when you swapped lamp assemblies, it worked fine.

Why would you defeat the bulb monitoring? I defeated it on my car because I'm running extremely long life LED lamps.

Cruise control needs to electrically sense the brake light filaments.

rgs944

The short was on the plug going into the bulb control. I could wiggle it and see the tail lights fade in and out. I might have been a delusional on whether I swapped it and it worked fine. My head was spinning 100mph at the time. After I got it back together I went for a drive and figured out the cruise no longer worked so I will be hooking that back up. I was just tired of seeing the warnings. Also with only going to a 2 wire system on the tails I was starting to think you needed to bypass it. Now I know that is not the case.