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Wiring gremlin on a 77 chevy

914 views 6 replies 4 participants last post by  Ortie666 
#1 ·
Hey, I just bouht a '77 chevy crewcab 350 4 speed and I have come across a problem. I was out driving it lass nite and after a while the dash lights would dim down, then the fuel gauge would drop, and the signal light indicators would light up along with the fasten seatbelt light.. so i pulled in the clutch and revved it a bit, and it went back to normal for a sec.. then it would go back to being goofy, then every once in a wile it would just snap back and i would have everything back. After a wile it would go back to being goofy., I had the same problem in a chevette a couple years ago.. I used to hit the stearing collom and it would go away.. for a minute.. so im assuming it might be a connection somewere..
 
#2 ·
It could be a loose connection someplace or a problem with the alternator/voltage regulator. You can see if the connection that goes to the back of the intrument cluster is loose or you can put volt meter off your alternator or battery and put it in the cab where you can see it that will at least norrow it down a bit.
 
#3 ·
Doc here, :pimp:

First , and foremost, grounding!!

Especially in "cold Country" ...

Take a day and set up a PROPER ground buss or you'll be plauged with this problem forever..

For your Ground Buss, Set it up as follows:

BE sure First, You have A 4 gauge Cable (for stock battery location, OR , 0/0 or 0/1 Cable for a trunk location) from the battery, to any handy bolt at or NEAR the starter on the block .

Using a short run to something like a seat belt bolt, or body bolt just adds resistance, the body is insulated..(has road paint and sits on rubber mounts) this , makes for a "Poor or no" Bonding situation..
  • that makes resistance..
  • Resistance makes Heat..
  • heat melts things and further insulates the bond,
  • which makes more heat..and so on..until you no longer have a good bond..

To install a proper ground buss system, This MUST be done:
  • 1 ) Run a properly gauged (0/0 or 0/1) Ground cable from the battery in the trunk, Or A 4 Gauge cable for a stock located battery, to any handy bolt at or near the starter on the block. From that same bolt get a 4 gauge Battery cable at the parts store, that has two 3/8 ring terminals on each end and attach it there and to the Frame. Make this run as short as possible.

  • 2 ) Next get some 10 gauge wire and ring terminals, run two wires from your bolt on the block, to the Firewall, Burnish off all the paint, grease or oil or dirt from the area, Install a sheetmetal or Self Drilling Tech screw using a star washer as well as a lock washer.. and the other 10 gauge wire to the Alternator ground lug, bracket or mount bolt and attach with star and lock washers.
  • 3 ) Next get some Wire Braid, (expensive! about $10 for 5 - 6 inch pieces! ) Check Radio Shack for this, OR cheaper yet, get some RG 8 Coax cable, about 10 feet. Should run you about 15 cents a foot.

HOW TO MAKE WAY DURABLE CHEAP GROUND BRAID:
--------------------------------------------------
  • 1 ) carefully Slit the insulation from the cable with a Talaban Boarding pass (box knife) .


  • 2 ) Peel away the insulation until you just have the center dielectric and braid left, then carefully press the ends of the coax cable BRAID together like a Chinese "Finger puzzle"


  • 3 ) Slide the dielectric and center conductor out. remove it and toss it..


  • 4 ) On a work bench, Flatten the Braided shield out, use a round weight like a full paint can to roll over it.
------------------------------------------------------

This will be your braid cable, just Cut to smaller length's as needed, and tuck the cut ends into a crimp terminal and crimp the ends on..

IF you can Solder, Tin the ends before you tuck the ends of the cable into the terminals, then Tin the barrel of the terminals, then insert the cable and crimp..

Then heat the terminal and braid, feed some solder into the opposite end as the heat is being applied, let it melt and FLOW or WICK toward the heat..until the terminal barrel is filled and is smooth and shiny..

that is a good joint..gray and rough is a "Cold Joint" and you'll have to start over..
  • 4 ) NEXT, install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body. Install a cable or Braid From the Fuel tank Ground lug where the sender, Fuel line is to the frame..burnish the frame, use star washers and sheetmetal or Tech (self Drilling screws) on the frame.

  • 5 ) At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.


It sounds like a lot of work, but after you assemble all the parts, it's only a few hours to do..and you'll end up with a system that will work reliably for many years to come..and can eliminate that from your troubleshooting list.

Remember: GROUND is the other Half of your 12 volt circuit AND is equally as important as having POWER to the device!

IF AFTER THAT:

You find the problem was not cured..

Check the regulator on the alternator..it may be shutting down too soon or just may be on the way out..if you have a place that does free testing, have it done..then repair / replace as needed.


Doc :pimp:
 
#4 ·
It still does it when its not running. when u just turn the ign. on the gas gauge works perfect, everything seems great.. if you turn on the windshilf wipers or the headlights the gas gauge quits, and the signal indicators come on.. Im not sure if it could an alternator or a ground problem but I will check them both and the conection box..
 
#5 ·
Doc here, :pimp:

Next place I'd look is the Column plug AFTER you eliminate the grounds and alternator..

Pull the plug and clean and burnish all the pins, inspect for bent or burned pins/wires, or ill fitting plug.

Doc :pimp:
 
#6 ·
The most common source of dash electrical problems in these GM trucks is the instrument panel ground. If its not making a good connection, you get a variety of symptoms as different accessories are turned on. Don't try to fix any other wiring problems until you are sure this ground is firmly attached.

The instrument panel ground is a black wire that is attached to the emergency brake pedal mechanism, which is then bolted on to the truck. If you look up under the dash at the top of the pedal bracket, you should be able to see the ground wire.

There is also a small ground wire on from the negative battery terminal to the right front fender, and a ground strap from the firewall to the back of the passenger side of the engine. There is also a ground for the taillight assembly (driver's side light?) that can cause problems with turn signals.

Bruce
 
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