Dash Illumination (backlighting) not working (1 Viewer)

Joined
Nov 22, 2005
Messages
208
Location
Minnesota
Hello,

my '94 FJ80's night time dash illumination is not working on anything. I've had an 80 series before (and the dash lights worked) but I don't recall exactly what should be lighting up to begin with.

I took the dash apart hoping it was bad or missing bulbs, but the bulbs look ok and test fine with an ohm meter. The HVAC heater/fan controls have 3 bulbs in them, and those do not light up either. Mini LEDs inside various buttons work (HVAC, power window, rear window defrost orange light), and my regular cluster gauge warnings/lights such as brake/oil/PWR/Gear position/turn signals/headlights and the d@mned ABS light (the ONE light I wish was NOT on). My next guess is the dash dimmer switch is bad but I'm not sure how to test it. Using a multimeter, I get 12V at one of the pins on the harness when I turn the headlight switch on. It's the pin by itself turned 90 degrees from the other 2 pins. But I don't know how to test the other 2. The digital dash clock works, and it even dims when I turn the headlights on, but I'm thinking that's on a different circuit. I do not have a repair manual at this point. I thought I did (from my last '80 series), but I can no longer find it. The radio is aftermarket and does not dim (and may not be capable of dimming). The truck had a stock alarm at some point but the RS3000 unit is missing from under the seat, but I see evidence of aftermarket wiring spliced into the "Security" light to the left of the steering column. The dimmer switch is plugged in. I even took it apart but didn't see anything visually obvious or wrong with it.

All fuses are ok.

Any ideas?
 
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Joined
Jan 20, 2013
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Bay Area, Ca.
Using a multimeter, I get 12V at one of the pins on the harness when I turn the headlight switch on.

All fuses are ok.

I just read this again, so maybe not the TAIL fuse.

Is the wire with the 12 volts green? (I don't have a '94 manual)
Jumper the other two together and see if the lights work.

(I assume you already checked that the dimmer wasn't fully turned down) :D
 
Joined
Nov 22, 2005
Messages
208
Location
Minnesota
I'll check the tail light fuse again, but I checked all fuses last night including under hood and didn't see any out. I had installed a receiver hitch a couple months ago and installed a 4-pole trailer adapter and tail lights worked back then (even though dash lights were still not working).

I don't remember the color of the wire I found 12V on, but the wire shows 12V when the headlight switch is turned on, and 0V when the switch is turned off. I'm assuming if I can see 12V here, than any ties upstream to the TAIL circuit probably means the TAIL circuit is functioning as well.
 
Joined
Jan 20, 2013
Messages
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Right, the positive side of the circuit is probably OK.

The dimmer (rheostat) actually varies the negative side of the circuit.

Try the jumper test I mentioned above.
 
Joined
Nov 22, 2005
Messages
208
Location
Minnesota
Will do, thanks! Hoping it's just a dimmer switch and not butchered wiring somewhere.

I am pretty sure I tried checking resistance across those two pins, and no matter where I turned the knob, it was always open. I never saw varying resistance. That being said, when I checked for resistance, I *thought* I tried checking every combination of the 3 pins, but I may have missed checking that pair. I checked varying combinations to see if I could see any fluctuation in ohms across any 2 pins (and didn't see any at all).
 
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Joined
Mar 25, 2005
Messages
2,120
Location
Edmond, Oklahoma
Do all the rear lights work? Running, Reverse, Brake, signals? I had the same problem on our 94 and I remember one of the rear light circuits not working as well. I'm thinking it was the reverse lights with this situation. If this is the case, I will tell you where to look. If not keep doing what landcrshr says.
 
Joined
Nov 22, 2005
Messages
208
Location
Minnesota
Ultimately it was the dimmer switch. Not wanting to pay $40 for a used faded Land Cruiser eBay switch, I figured and hoped Toyota still had some inter-changable parts going on between models back in the 1990's. So, I looked at dimmer switches for 4Runners, pickups, camry's, corollas, and AHAAA--CELICA's! I found a 1992 Celica dimmer switch, EXACTLY the same in every way. Bought that for $15 instead and problem solved.
 

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