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Electrical & Wiring Troubleshooting electrical problems.

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  #1  
Old Apr 6th, 12, 7:51 PM
Ron's69SS Ron's69SS is offline
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Ron
 
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Location: Wellsville, NY
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Default Gauge problems

I'm thinking about pulling my '69 dash tomorrow to dig into problems with my gauges. Here's how they're acting:

Temp seems to work alright.

Oil Pressure stays past "H" all the time, moving up slightly only when the ignition key is turned on.

Amp gauge hasn't worked in two years - the needle rests at the bottom of its swing.

Fuel gauge works well enough.

Clock works, but is fast.

Is there any common solution to all this? Could it simply be inadequate ground?

Would appreciate any experienced advice.

Thanks,
Ron
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'69 Chevelle SS, 396/325JA, 4 spd, 2dr Coupe, Cortez Silver, Blue vinyl top, Dk Blue interior, U-46 Light monitoring, AC, bucket seats, 3.31 12-bolt posi.
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  #2  
Old Apr 7th, 12, 1:10 PM
larrygk larrygk is offline
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Default Re: Gauge problems

I'm no expert by a longshot and it is the good suggestions of the TC members that helped solve all of my stuff (fuel sender, alt light in particular, alternator and VR itself), and a good copy of the factory schematics, but what you will read is these things come from 3 basic categories (obviously):
1) Bad grounds or the main ground bar (don't know if your year has one) under the dash.
2) a bad gauge(s)
3) no power somewhere in the circuit

In my case there was NO commonality. Each problem had its' own characteristics and fix. Start with the schematic and define what wires give each of your gauges ground and power. Sometimes the question becomes should such and such wire be hot all the time or not.
And of course applying power to a gauge or measuring resistance is a key test.
Anyway, I wish I had a clock period..fast or slow.
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Old Apr 7th, 12, 1:45 PM
Ron's69SS Ron's69SS is offline
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Ron
 
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Default Re: Gauge problems

Thanks. I'll just go through each one individually. I forgot to mention that the tach works, but only when it wants to; which says bad ground to me.
Ron
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'69 Chevelle SS, 396/325JA, 4 spd, 2dr Coupe, Cortez Silver, Blue vinyl top, Dk Blue interior, U-46 Light monitoring, AC, bucket seats, 3.31 12-bolt posi.
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Old Apr 9th, 12, 6:50 PM
Ron's69SS Ron's69SS is offline
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Ron
 
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Default Re: Gauge problems

I've narrowed things down some. The Tach was the victim of a loose connection - works fine now.

Oil Pressure gauge is weird. The wire colors are correct and connected properly. I hooked up a new gauge-type sender at the engine, but it makes no difference. When the ignition key is turned on (not to start), the needle jumps past "H"; when the key is turned off it slowly creeps back to about the 3/4 mark.

The Amp gauge is another mystery - the needle just lays there dead. There are no wires color coded as they should be. Only one wire (black with grey stripe) was connected; there was nothing attached to the ground post; nor does there appear to be an extra pink or ground wire loose anywhere. I found a toasted wire running through the harness melted to the black\grey wire that was attached. And I found another wire attached to nothing under the dash that ran out near the battery and was connected to nothing there; not wrapped in with all the others.

Thanks for any help.

Ron
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'69 Chevelle SS, 396/325JA, 4 spd, 2dr Coupe, Cortez Silver, Blue vinyl top, Dk Blue interior, U-46 Light monitoring, AC, bucket seats, 3.31 12-bolt posi.
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  #5  
Old Aug 7th, 12, 11:46 AM
Chevelle Freak Chevelle Freak is offline
Rian
 
Join Date: Mar 2008
Location: Southern Illinois
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Default Re: Gauge problems

I had a problem with my amp meter in my '70 Chevelle and couldn't find the answer anywhere until I spoke with an automotive electrical specialist in California. He said that the ampmeter measures the difference between amperage at two different points in the car's electrical circuitry and is NEVER connected to a ground. Grounding one of the two wires on the gauge will either burn the wire, ruin the gauge, or burn the circuit board. In my case, the circuit board was burned.

He said that the wires that are connect to the instrument panel circuit board are included in the connector under the steering column. I can't quite remember the colors but I think that one is black and one is black and gray or just gray. These wires run to the engine compartment and attach to connections on or near the radiator support. The black wire connects to electrical junction block near the battery and the other connects to the horn relay on the opposite side of the radiator from the junction. The gauge then measures voltage rise/drop between the two connections.

The problem arises when a person disconnects the front wiring harness and then reconnects it. The black wire near the battery looks like it should be a ground and is the right length to attach to the headlight ground screw. This creates a dead short. Check this out and correct if it is the problem. Then, if the circuit board is burned, you can probably attach new wires (with small inline fuses) directly to the gauge terminals and attach to the appropriate wires in the harness below the steering column. This bypasses the burned circuit in the instrument panel and worked perfectly for me. Good Luck.
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