Dash Illumination out

[redX90]

I searched many threads on this subject but there are no solutions. I was cutting out the spaghetti wire harness in my 1G GSX that previous owner did to the stereo and that night when I turned the headlights on, no dash or console illumination. There are no blown fuses anywhere. Everything else works. All relays in any way related are good. I've got a good factory harness installed for the stereo now and stereo is fine. But still no illumination. I've been through my back up CD's schematics racking my brain trying to figure out how everything else attached to this circuit works fine. I will check the dimmer switch tonight though I don't think thats going to go anywhere. Has anyone actually found the source of this problem?

 

[Lordpaxin]

engine bay [] fuse box [] fuse labeled TAIL

10amp i think

 

[redX90]

Thanks for the input. Wasn't a fuse. All illumination was getting power. It just wouldn't go to ground. I swapped out the rheostat and that solved the problem. I'm going to take it to work and see what actually blew inside so I can fix it next time.

 

[GTM]

Originally posted by redX90
Thanks for the input. Wasn't a fuse. All illumination was getting power. It just wouldn't go to ground. I swapped out the rheostat and that solved the problem. I'm going to take it to work and see what actually blew inside so I can fix it next time.

Just a reminder, some radios have day/night illumination control. In the daytime it gets power from one circuit, at night it gets it from the dash lights. One possibility if he had all or part of the dash ground running through that radio circuit and you cut it, good bye dash lights. Another possibility is it was a hot lead and while in the process of removing it touched to ground, poof their goes the dimmer especially if it's transistorized. You wouldn't need to see a flash and may not have blown a fuxe for a couple of them are about the size of a pencil eraser.

Let us know what you find.

Cheers,
GTM

 

[redX90]

I took it apart and chekced it under a 40X Stereo Scope. Nothing is burnt. Every part checks good in circuit, that is no open or shorted transistors, diodes, resistors. Pot is good. Weird. Even if I did find a part bad on the pcb to recommend for a fix, not too many people out there can handle these tiny surface mount componants. Oh well, thankfully I had a spare in my parts car. I don't know about availabilty of this part so in the future I would recommend just getting one or two out of a wrecking yard if this occurs. I'm not sure but since it was the ground that was corrupted, just bypassing the dimmer and running the black / yellow wire to ground might correct the problem.

 

[GTM]

Originally posted by redX90
I took it apart and chekced it under a 40X Stereo Scope. Nothing is burnt. Every part checks good in circuit, that is no open or shorted transistors,
...
I'm not sure but since it was the ground that was corrupted, just bypassing the dimmer and running the black / yellow wire to ground might correct the problem.

Hey, lucky you 40x stereo scope sounds like you gave it a good try. I've not had a lot of success testing transistors while still soldered to the board. Unlike a lot of other designs these are a current limiting transistors if memory serves me correctly. I don't think they are a NPN or PNP type which most multimeters can test these days.

Needless to say I've had my share of grief with these circuits and even wired a couple on my boat. They may also be part of a floating ground circuit that's tied in with the bulb check circuit which I don't think the people who designed that even knew what they were doing. hehehe

Cheers,
GTM