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Old 03-22-2005, 06:28 PM   #11
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Default Dashlights out....more troubleshooting...

Thanks for the reply Andy. Mine is an '88 so slightly different but here'* what I found: on the main headlight switch pod there are 5 wires: A brn, B blk, C red, D yel, E org; switch off B, C & E are all +V hot with A & D <1 VDC; the headlight switch has two segments, when the black segment is turned on the headlights power on and wire A goes to +V; when the small grey segment is turned on D goes to +V. This tells me that I have hot +V to the switch and both outputs (headlights and fog lights) are both getting their +V to turn on. Headlights come on but no fog lights. (that'* probably another problem) Next the panel & interior lamp dimmer switch has four wires: A brn, B blk, C wht, D brn. With the headlight switch off C is +V and A, B, D are < 1.0 VDC; when the black or grey headlight switch is turned on D goes to +V and A is variable +V based on dimmer rotation, B stays low at all times. The interior lamps function normally when doors are opened and/or the dimmer is rotated, but there are never any dash lamps.
It seems to me that this indicates that my headlight/foglight switch is receiving + 12 volts and switching it correctly, the dimmer is receiving the +12 V from the head/fog lamp switch and switching it correctly, but something is killing the +V en route to the dash or the dash itself is not working. I'll try to see if I can find the switched +V on the large dash cnnector...if +V is there then that will indicate bad dashboard...right? Thanks for the reply and I'll let you know what happens.
PS, sorry to take so long to reply but I was outta town for two weeks.

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Old 03-22-2005, 09:58 PM   #12
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Did you check the relay center on the passenger side of the car? I think there are abou 8 fuses there, including the foglights.
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Old 03-22-2005, 10:42 PM   #13
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Default Re: Dashlights out....more troubleshooting...

Quote:
Originally Posted by Hoobastink
Thanks for the reply Andy. Mine is an '88 so slightly different but here'* what I found:
Not too bad: most of the color coding has been standard for years...

Quote:
on the main headlight switch pod there are 5 wires:
And they are (based on the '93 book):

Quote:
A brn
Switched lighting output (full voltage) for all exterior lighting except headlamps, and input to the dash backlighting rheostat

Quote:
B blk
Output to lamp control module (Twilight Sentinel)

Quote:
C red
Headlamp power input

Quote:
D yel
Headlamp power output

Quote:
E org
Switched lighting input

Quote:
switch off B, C & E are all +V hot with A & D <1 VDC; the headlight switch has two segments, when the black segment is turned on the headlights power on and wire A goes to +V; when the small grey segment is turned on D goes to +V.
I don't totally follow this part; it may not apply to the '93. I expect A to be hot at all times as in the '93 it bypasses the switch and goes straight out to the lamp control module. Whatever...

Quote:
This tells me that I have hot +V to the switch and both outputs (headlights and fog lights) are both getting their +V to turn on. Headlights come on but no fog lights. (that'* probably another problem) Next the panel & interior lamp dimmer switch has four wires:
Okay...

Quote:
A brn
I don't have this one, but see below...

Quote:
B blk
Ground, applied to your interior lamp circuit to turn them on (they're on a switched-ground circuit)

Quote:
C wht
Switched-ground interior lamp input. When the switch connects this to Pin B above, your interior lights go on.

Quote:
D brn
Don't have this one either, but I can make a guess...

Quote:
With the headlight switch off C is +V and A, B, D are < 1.0 VDC; when the black or grey headlight switch is turned on D goes to +V and A is variable +V based on dimmer rotation, B stays low at all times.
Okay, A is your variable dash lighting circuit, as you suspected. It feeds your gray wires in the dash. If it'* hot right there with variable voltage, start tracing it (with a needle probe and test light, not just a voltmeter) and see where it goes.

C is your interior lighting circuit, looking for a ground path. B is the ground path it'* looking for. D is, I think, a "Lights Are On" signal circuit that probably tells fluorescent displays such as the stereo to switch from their full-brightness to variable-dimming display settings. I think you may find a brown wire at your stereo connections; it'* probably a branch of this circuit.

Quote:
but something is killing the +V en route to the dash or the dash itself is not working.
Yes, I would check the one or two large harness connectors going in the back of the gauge cluster. Also find gray wires somewhere -- anywhere -- and check their voltage. (You can probably find some behind the dash or in the console.)

I don't think you're real far from figuring this out. I would not replace the dash cluster just for this, as the bulbs just stick in the back of it. Also, even if the cluster itself was bad, you would see some dash lighting elsewhere, and right now you're telling us that you see no variable lighting at all.
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Old 03-25-2005, 01:01 AM   #14
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Default dash lites out...help!!!!

Thanks again Andy. Greetings from South Beach. Took the dash out and looked at the main instrument cluster connector... tried to find the variable +12 VDC output from the instrument panel intensity rheostat............nope, not there . I really thought I should find the variable +V referenced to ground but got zip..this seems to indicate a break in the path to the instrument lites...which just might go back through the fuse panel...maybe I've got a loose connection on a fuse? Gotta catch an early flight home tomorrow. I've got a test lamp with a sharp tip so I'll spend some time on that this Sat morn...if it doesn't rain. I NEED to sell this car so I can pay the attorney. I'll let ya know what I find.
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Old 03-25-2005, 01:29 AM   #15
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Default Re: dash lites out...help!!!!

Quote:
Originally Posted by Hoobastink
Thanks again Andy. Greetings from South Beach. Took the dash out and looked at the main instrument cluster connector... tried to find the variable +12 VDC output from the instrument panel intensity rheostat............nope, not there .
Well, try identifying the variable output lead at the headlamp switch rheostat, and also _any_ gray wires you can find behind the dash (including the harness connector, at least one wire of which should be gray).

Quote:
I really thought I should find the variable +V referenced to ground but got zip..this seems to indicate a break in the path to the instrument lites...which just might go back through the fuse panel...maybe I've got a loose connection on a fuse?
Maybe, but I doubt it. (You have _found_ the dash lighting fuse, right?)
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Old 03-26-2005, 06:52 PM   #16
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Default Dashlights out....more troubleshooting...

"You have _found_ the dash lighting fuse, right?)"

Yeah, and it'* ok...rats! Of course I was hoping for an easy fix. I wanna pull the fuse panel and interrogate the back side wiring. I've had to do a lot of travelling this week and next week looks the same unfortunately. Gotta visit Oklahoma City, Louisville, Toledo, and Indy. *'posed to rain here tonite thru Sunday, maybe I can look at it Monday. I'll keep you up to date. Thanks again.

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Old 03-26-2005, 10:27 PM   #17
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Default Re: Dashlights out....more troubleshooting...

Quote:
Originally Posted by Hoobastink
"You have _found_ the dash lighting fuse, right?)"

Yeah, and it'* ok...rats! Of course I was hoping for an easy fix. I wanna pull the fuse panel and interrogate the back side wiring.
That'* easily done. If you take a good look at the hinge where the fusebox swings down for access, you can see how you can pop it completely off.

Realistically, I don't think there'* much to see back there, though; if the the fuse sits tightly in the clips, and one of the two clips tests as hot when you have the fuse out (and have switched on whatever the circuit is), then that'* about all there is to it.
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Old 03-28-2005, 09:32 AM   #18
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Default Dashlights out....more troubleshooting...and a fix!!!!!

OK, I've got lights!!! I spent some time yesterday with the DVM and a beer and came up with this fix: pulled the fuse panel to see the wiring arrangement on the back side and everything was OK as you expected...but having the fuse panel out to play with allowed me to look at more of the wiring and later to simply run a redundant dash-lite circuit...I was unable to find the variable +12V output from the rheostat on the dash lite fuse (brown wire at both ends)...unable to ohm out continuity (same wire but with power switched off)...but I was able to get continuity from the fuse to the dash board connector (green wire both ends). I concluded that there is a break in the brown wire from the rheostat to the fuse panel. With an alligator jumper I went from the fuse to the rheostat and presto! lites!! I spliced in a wire from the correct side of the fuse to the rheostat output and put it all back iogether and that seems to be the fix. I say seems to be the fix because I couldn't make sense of the wiring diagram in the Haynes manual compared tio the wiring in the car...but it works without any smoke coming out from under the dash so I'm happy. Thanks for all of your suggestions and tips. It helps to have another head figgerin' things out.
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Old 03-28-2005, 11:52 AM   #19
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Default Re: Dashlights out....more troubleshooting...and a fix!!!!!

Quote:
Originally Posted by Hoobastink
I concluded that there is a break in the brown wire from the rheostat to the fuse panel.
I guess that doesn't totally surprise me. Maybe there'* some aftermarket silliness in the car'* past that might have something to do with this.

We had a case here a while ago where, if I remember right, some alarm or remote-starter installation outfit had cut the exterior lighting circuit when installing their box. i.e. They hadn't just teed in their wire for blinking the lights to acknowledge a command or whatever; they had _cut_ the original supply wire instead, so that the lights were _completely_ controlled by the box, and only the box.

So then of course somebody took the box out...
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Old 03-28-2005, 12:21 PM   #20
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That'* a good one...imagine getting some bogus wiring at a stereo shop!!! I once bought a nice little 280Z that had a secret kill switch installed under the dash...it interrupted the reluctor signal from the distributor pick-up coil. When turned off, the car would turn over just fine but never get the timing signal needed to fire the coil...which worked great until I forgot about the switch and burned up the starter...twice! You know, rrr-rrr-rrr until the starter fries then buy a new one and burn it up trying to troubleshoot...then remember the kill switch.

Now that'* one way to kill the ignition and keep somebody from trying to easily steal the car but there are better ways to disable the ignition and not leave the starter working. By the way, the original modifier had split the wiring harness cover, added the kill circuit and re-wrapped it with tape which then got covered up with road dirt and looked OEM. I finally had to de-install the switch when it went bad and just keep the thing insured. Fun little car, wish i still had it.
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