moosemobile

I'm new to this site and I need some help with some electrical problems. I just bought a 2006 V6 coupe and I'm trying to fix the issues that came with it. It has two electrical problems. 1. Rear window defroster does not work. 2. Trunk light does not work. I have checked the fuses and all are intact. I'm tackling the trunk light first. When I put a test light on the plug for the light, it does not light up. When I push the switch rapidly many times, the test light flickers but does not stay on. Any ideas? Thanks for your help.

Avalanch3

There is a problem with our cars and leaks. Check under and around the mat on the passenger side, is it damp or wet after a rain? This can cause electrical problems in the car, and there is a TSB for it.

moosemobile

Thanks for the info Avalanch3. This is interesting because in the dealer service paperwork I received with the car, there is a listing for water getting into the car and that it was fixed. I looked up the TSB on this site and I don't see one for the fuse box. I see 08-26-7 for water leaks, but it does not address electrical issues. Is there one specific to this problem? Everything else works great; trunk release, windows, alarm, etc, would it make sense that just the trunk lid light circuit would be affected by a water shorting problem? Any help is appreciated, thanks.

musty ruffler

Sounds like you might have at least one loose ground somewhere. Easiest way to hunt electrical gremlins is with a cable tracker; aka a cable tracer or wire tracer. It's a two-piece gadget- clip one piece to the wire or circuit that should have continuity but doesn't, then use the "magic wand" to follow it back until it stops beeping- that's where the fault is.

Remember that trunk light is 12v constant, so best safety practices suggest you should disconnect the negative battery terminal before digging around too much.

That said, a water leak can definitely cause only one circuit to fail, at first. Just depends on where the corrosion builds up. Experienced this recently in my new apartment, where a water leak onto the breaker box had hosed the breaker for one room of my place. Corrosion existed on the other breakers, just hadn't gotten to that failure point yet.

Nuke

The TSB doesn't specify symptoms since the SJB can oxidize in so many different places that the symptoms can vary tremendously. Most folks seem to report windows, door locks and other electronics gremlins.

From your description of the light flickering, I'd check to see if the voltage before the switch is steady. It sounds more like a switch or loose wire issue. For the rear window defroster, begin checking for voltage at the connector to the grid at the window and work back from there.

157dB

The trunk light is NOT 12V constant....
Breakers are non-existant in the S197....
cable trackers only show wire breaks, not SJB corrosion....

First I would check Fuse 59, 30A in the BEC for the trunk light power.
Next I would check the G400 ground right under the trunk lock area.
Then leave the trunk open and see if the trunk is ajar light comes on
with the key in the run position. If so, the switch is good as well as
the wiring to the SJB.
As for the defroster,
First I would check Fuse 52, 30A in the BEC for the rear glass defroster.
I would then check for ground on the white wire at positon 12 on connector
C2280C at the SJB or the white wire in position E3 on connector C1035A
at the SJB when defrost is being requested by the SJB.
Then I would pull the defroster relay and check for resistance on the
wire going back to the defroster grid. If thats good, jump 30 to 87 on
the plug for the defroster relay.

Mostly I would say that your SJB is T O A S T.

musty ruffler

I meant "switch," but that diagram has me confused. "Hot at all times" -> SJB -> trunk ajar switch. But this is good info, and more complex than the simple relay I assumed was being used.

Right, I was analogizing to illustrate corrosion damage. That said, I don't see how corrosion at the SJB would cause a situation where the light would work when the switch was jiggled?

157dB

Corrosion and modern electronics are a very weird unpredictable
thing when introduced to each other. Thats how corrosion could
cause a situation when the light would "When I push the switch
rapidly many times, the test light flickers but does not stay on".

moosemobile

Thank you for all the helpful ideas that have been posted. I finally had a chance to get back to the trouble shooting today and followed 157db's suggestions. Fuse 59 was intact and showed continuity when tested with an ohm meter. I'm not sure what G400 is exactly, but I checked the ground going to the trunk released (which works) then took the power from that plug and hooked the ground to the trunk lid light plug and pushed the trunk release button, and the test light came on so the ground going to the light is good. The trunk ajar light does come on with the trunk switch disconected. I tested the light plug with the meter and measured .19 volts. I removed fuse 59 and measured 163 millivolts. So.... I'm thinking that since I'm getting voltage with the fuse out, it must be a short somewhere and the logical place for it to happen is the SJB.

Part two of this is that when I pulled off the kick panel to start checking out the SJB, I found water under the carpet. The whole pad under the passenger side was soaked. I took it to the dealer that supposedly fixed the leak the first time and they found two new leaking areas (passenger window weather stripping and door weather stripping) Cost to fix - $600 plus. Ford refused to help in any way. The dealer didn't charge me for finding the leaks, so I'm grateful for that and at least now I know what to fix for that problem.

Thank you 157db for the step by step directions. Very helpful. And I'm afraid you may be right about it being toast. I will finish tracking the problems back to the SJB to make sure this weekend I hope. Just no time again until then.

One more question on this: is there a fuse in the SJB for the trunk light (I'm thinking there must be for it to be affected by the SJB) and if so, which one is it? As you all know, the owners manual does not designate it specifically. I figure if I can measure the voltage across the fuse with and without it in, I will know for sure if it is bad or not.

157dB

No fuse in the SJB for the trunk light.
Only in the BEC.