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Old 09-06-2004, 02:28 PM
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Unhappy Dash Board Gremlins!!

I was taking the old radio out of my 1991 Sonoma (originally with the 2.5) and must have pulled something loose. The dash harness seems totally possessed !!

The gages look like they are all reading a little lower than they should. The voltmeter, for example now reads maybe 10 volts (you know how hard it is to estimate that thing), but when I check across the battery terminals I get 14.7 v running and 12.8 not running. When I turn on the headlights all the gages dive south and drop off the map...volts, oil, gas, temp!!! The headlights are also dimmer than they should be, but brake lights look normal.

I'm using a taurus electric fan running on a seperate circuit with its own relay and fuze. When it cuts on nothing wiggles on the gages. I'm guessing this means the problem is on the inside with the underdash harness.

I think the generator is charging the battery OK, at least those voltages look pretty good.

The main power leads from the junction block to the big firewall connector next to the brake booster are OK and still hot.

I took the dash out this morning and cannot find anything obviously loose back in that rat's nest of wire. I noticed a large multi-prong grounding plug mounted on the steering wheel support with nothing plugged into it. I looked for a matching female connector and didn't find anything, but it could be buried somewhere. Even with the dash loose and on the floor it's still hard to see back there...especially with the temperature in my driveway hitting the high 90s.

I'm wondering if I pulled a ground loose? Does all this wierdness sound like that to any of you?

Believe me...and suggestions will be appreciated,


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Old 09-06-2004, 04:26 PM
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Doc here

YUP...I got the Same Problem on one of my Vettes,

I know for a fact that, one of the Radio's is supplying power through ground to something else..
(Loaded Ground)

But haven't had time to Find it yet...

It's between the Dome lamp And Radio's Harness circuits, Dome works fine (Even with a blown fuse) until you turn the headlights,and dome light, then tail lights fuse blows out..

What I did find, That on the Corvette, anything Green in color was a DIMMER Circuit not a ground...ALSO all the circuit switching on a Corvette is actually GROUND not Power. ...And this started the problem.

So if yours is the same you may have the same problem too..

First check ALL of your fuses.

If you have a blown fuse, and something wired to the "Hot side of a ground" you can pull a LOWERED amount of current through that item to power the next item using it 's ground to run both (LOADED GROUND)like wiring several 12 volt light bulbs in series...they will run, but dimmer then normal.

Essentially, you will get power from the last item not fused back~feeding the blown fuse circuit,(usually Via a Miswire) from its ground to power the next item.

I hope I didn't confuse you here, It's kinda hard to describe...

Best thing to do is check the fuses first noting any blown ones..Replace it and see if it blows again..

Next Double check your radio harness and be sure you don't have a miswire there (like drawing power from a dimmer to a ground wire in the radio..) and see what you find.

Be sure all your grounds are correct and good. You should find the problem.

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Old 09-06-2004, 04:41 PM
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Radio wiring

Doc's right on. Check the gauge & courtesy fuse. If you factory radio had the 2 plug connector also which is a black & orange wire make sure you seal the ends so no accidential contact to these can be made. The orange wire Circuit #412 is a power wire that runs the clock & light on the radio and runs to almost every accessory on the truck.
Good Luck---------
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Old 09-06-2004, 05:34 PM
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Thanks for the advice, Doc and Resto. I checked the fuzes and nothing was blown. When it cools down a little I'll look for a ground pulled loose. What you said makes a lot of sense, Doc. I'll bet that's why trailer lights get so wierd when there's a bad ground. I never thought of grounding through another accessory.

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Old 09-06-2004, 06:45 PM
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Good call as usual Doc......................most dash problems are traced back to a bad ground.
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