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1979 CHEVY C20 3/4 TON ELECTRICAL PROBLEM

  
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1979 CHEVY C20 3/4 TON ELECTRICAL PROBLEM

 
steeledef steeledef
New User | Posts: 2 | Joined: 05/09
Posted: 05/24/09
08:56 PM

basically this is how it goes.. as of today none of my gauges work at all but yesterday they worked just fine..when i turn on my headlights, my gas needle slowly goes to the E empty line on my gauge when i turn them off.. the gauge reads what its supposed too.. none of this happened until i tried to reground my ignition module on my firewall.. when i connected the battery post it smoked a little and sparked.. so what i did was take the temporary ground off the firewall and left it alone.. did i fry my electrical system on the whole truck or just the instrument cluster? is there anything wrong at all? i did crank the truck i have turn signals,lights, etc. everything is operational.. any suggestions to how to fix my electrical problem?  

jalopy45 jalopy45
New User | Posts: 40 | Joined: 03/09
Posted: 05/25/09
12:06 AM

Sounds sorta like a short problem, maybe frayed insulation?  I'd start by using an ohm meter and check as many wires as possible with the batery disconnected. If a wire shows continuity, trace it and check all the points where it crosses over or thru any metal. Start at the distributor and then the headlight wiring as it seems to be the center of the problem.  Electrical problems are a major cause of balding and gray hair.  

steeledef steeledef
New User | Posts: 2 | Joined: 05/09
Posted: 05/25/09
12:55 AM

no the wires are just fine.. even the harness and plastic tubing on everything.. it just dont make any sense you see everything worked fine till i *** with the ignition diamond on my firewall and the procedure was as simple as fixing a ground that wasnt properly connected.. i think when it smoked and popped it fried the damn harness.. i dont know.. but i mean how is that possible at all when you turn on the headlights.. the gas gauge moves all the way down to empty.. and also i think that my wiring  might be faulty just outside of the instrument cluster you know where the gauges plug into.. any suggestions how to fix that? replace the instrument cluster? or replace the gauges? or replace the whole assembly and check for bad wires on the circuit board  

Thespecialist Thespecialist
Enthusiast | Posts: 358 | Joined: 10/08
Posted: 05/27/09
11:05 AM

On a lot of gauge clusters there is a voltage regular. If you damage that your gauges will go haywire. Also generally you power up one side of the gauge and the ground to the sender unit will determine what the reading will be. If you want to check each gauge you will turn on the ignition switch to "on" and take the wire for example that goes to the top of the sender unit on the motor (e.g temperature), disconnect it from there and touch the wire to the motor or somewhere ground. The gauge will go up until it reaches the top. Now some gauges work the oposite way, they will go to the lowest reading.
  If you played with the ignition switch you may have no power to the gauges. But as I said, some work in reverse. This is where you need the manual and the wiring diagram, that will tell you if there is a voltage regulator on the back of the gauge cluster.