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Discussion Starter #1
This is beginning to look like a job for Mr. T, and I’m not looking forward to the mess. Any help would be appreciated.
My combination meter assembly (the gage cluster) had several lights burned out on it when I bought the vehicle. Last week I replaced all of the burned out lights, and ta daa – no lights at all anymore. The turn signal indicators work. The gear shift indicator LCD lights up (SMT), even all of the lights on the heater control group work, but I have no back up combination lights anymore.
Some more specifics for you experts. I have a good ground to the system and power to the positive side of each of the light bulbs. All bulbs have been tested and work correctly. However, no light wants to work.
I’m stumped, and I’m thinking that Mr. T is going to want to replace the entire combination meter at a high price.:eek:
Am I looking at a failure of the circuit board? Anyone have an idea for me? I’d really appreciate it.

Thanks,

Fox
 

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Sounds like you know how to do some troubleshooting. Have you looked at the BGB wiring diagrams? I will admit I don't fully understand how Toyota multiplexes power to curcuits, but they do seem to do it.

So, a good place to check (assuming speedo/tach/etc work) for an all lights out condition would be the dome light 10A fuse (using the 2002MY BGB ). That's in addition to the 7.5A fuse that's actually labeled Gauge. Both of the fuses are shown to provide a power lead to the various combination meter lamps.

The BGB shows those two fuses controlling ABS, oil, brake, fuel, p/s, charge, door seatbelt, R, N, cruise and malfunction indicator LEDs, plus a bulb for the SMT. Turn signals use a different power source.
 

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Discussion Starter #5
Still not working.

Kev,
I replaced all of the lights. Then put the original ones back in. Then replaced them ALL with new ones. Then replaced them all with a combination of new and old. Each and every light was checked for polarity and working condition. Each light GETS POWER when the light switch is kicked on. None of them light up! I’m sure it’s a grounding issue, but all of the grounds to that panel are good. I’m beginning to believe I’ve got a cracked circuit board that’s not letting that part of the system ground out.

EGS,
Dimmer’s cool. Proper output and input. Meets the BGB’s specs.

Lbridges,
Fuses are good. I replaced a few in my hunt just to be sure and then checked them all one at a time.

Here’s the weird part. Only the combination meter is affected, and the rest of the dash operates normally. It even dims as it should. The turn signal bulbs work perfectly and the SMT shift designator works as well. So do all of the warning signals on the combination meter. Just no illumination!

I’m one to normally overlook the forest for the trees, so I was just checking to see if there was anything major I’d missed, like some kind of oddball fuse able link or something.

Thanks for your input guys – I’ll keep you posted on this one.

Fox
:cool:
 

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I'm still not following. Are these lights for illumination of (so you can see at night) the combination meter or lights in the meter for various things?

Anything that has variable illumination has two wires going to it, one is 12V all the time and the other has 0-12V (variable). There is a transistor in combination meter for that. I posted about it a while ago... quoting myself:


"For the illumination, I tapped into the Green and Green-White wires going to the fog light switch. That's one of the things that dim when you turn the dimmer near that. These two wires (G, G-W) come out of the instrument cluster. The Green wire has 12V when the headlights/taillights are on. The Green with White stripe wire actually controls the illumination by varying from 0V (ground) at the BRIGHTEST illumination level up to 12V at the DIMMEST level. "

So look in the wiring diagram for where the Green and Green-White wires come from.
 

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Discussion Starter #7
Kev!
I've got power to the bulbs. Each and every one. I've tested them in place with a meter and a test light. The power works as it should. The power leads to the board are good, as is the ground lead. For some reason I'm having a grounding issue on the board directly. I'm not that great at tracing circuits on the board (bad eyes), but I'm guessing that the board is toast at some point. Perhaps one of the components has cooked or something. Before I go to fantastic lengths at board trouble shooting I'm going to try to find a used board (or entire combination meter) and swap it out. If things get REALLY bad I'll take the good one out of my 2003 and try swapping that, but I don't want two copies of the same problem if I can avoid it.
Just to clarify, is there any way I can bypass the dimmer rheostat? If it works on a variable ground rather than a variable positive perhaps that's my problem.
I really appreciate your interest and comments!

Fox
 

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Discussion Starter #8
Fixed!

Yeah, it was a break somewhere in the board. I actually took things in hand and soldered a couple of lines to the board where it put power directly to the light bulbs and then tapped into the lines that Kev suggested. Bingo! I now have dash lights. Not dim-able, but beggar's can't be choosy, and I'm darned glad to have lights at night now!
Thanks for your support guys - I managed to dodge a bullet once again.


Fox
:lol:
 

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That's mostly good news.

Gives you time to decide if you want to just live with it, look for a replacement part from a yard, or whatever.
 

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Whoops, I missed your 6/14 post. Yes, the "grounds" are variable. Not really grounds. Voltage is a difference in potential. So if you have 12V on one side (relative to ground) and 5V on the other side (relative to the same ground), that's 12-5 = 7V across the lamp filament (or whatever) and it will be dimmer than if the other side was a lower Voltage (like 0).

Glad you found a reasonable fix. I guessed the problem was the transistor that provides the variable voltage on one side of all the lights (and you were talking about the illumination lights). It wouldn't be that if other things dim, though. That would prove the transistor is good. I should have asked if other things dimmed with the rheostat.
 
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