Electrical question, am I on the right track?

nowherefast77 · **Joined:** Tue Dec 30, 2014 1:12 am **Posts:** 13

OK, this is for all you service techs and electrical/can buss gurus....

So my fuel Guage back light doesn't work... Well...the light itself DOES work, it just doesn't 97ish% of the time. Now we all know the bulbs are actually computer controlled led's, (08 and up) but looking at the schematics they're still "wired" if you will... In parallel. What I can't quite tell is do they all share a common ground?

My fuel gauge back light acts like it's a common everyday bad ground. It'll flicker a few times, come on for awhile and then flicker off. Though that happens rarely. It's usually off. The needle lights up and the gauge itself works just fine though. Now my theory is if they DO all share a common ground then I doubt a bad ground would be the case as they'd probably all act the same way. ie when my trailer harness ground came loose I had no trailer lights. So in that case I'd think maybe bulb/socket coming loose from board itself? BUT if they didn't share a common ground then I where would look as far as grounds for the dash lamps? Assuming all power, signals etc come from and go to the connector in the back of the dash instrument cluster wouldn't the grounds/ground also be in that connector?

PALiftedKK · **Posted:** Wed Dec 23, 2015 3:14 pm

What???

Cabin ground for the front dash uses a common rail. The led is most likley burnt out or is overheating thus melting and cooling the solder

nowherefast77 · **Joined:** Tue Dec 30, 2014 1:12 am **Posts:** 13

The led works. It's definitely not burned out. Sometimes it'll come on if I change the dimmer setting. Other times it just comes on on its own. It's a connection issue. I know that much already. Question was if the cluster lights use one ground or individual grounds. I guess it would've just been simpler to have asked that 1st off. But I wanted to explain the problem and that for the most part I understand the wiring. Just not 100%

That explained, if you're saying they all use a common ground wire, do you know where the ground is and what pin it is in the connector? And where it actually grounds to?

And THAT said, I'm still a little sceptical on all cluster lights using one ground. If they all used one ground, and that ground was a bad connection then I'd have an issue throughout the entire circuit... ie all the cluster lamps. Hence the reason for most cluster gauges being wired in parallel. It's specifically done so you don't lose all your gauges at once. Also the red needle is back light all the time even when the white back light is not.
I COULD see solder melting IF the lamp was on, got hot and went off... But that's not what's happening. In fact it's usually kinda the opposite. It's starts out off, then randomly turns on. So it CAN'T be melting solder making the connection loose.

(which I just now realize after explaining is also answering one of my original questions.)

PALiftedKK · **Posted:** Thu Dec 24, 2015 8:56 am

May just be the pin in the circut board or connector got loose then. Try to reach through under the steering wheel and attempt to find that connector.

Electrical question, am I on the right track?

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