Electrical Gremlins (longish)
06-07-2001, 08:33 PM
#1
Track Day
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Electrical Gremlins (longish)
After many frustrations, the temp guage, and all the other guages, and, indeed the electrical system as a whole is working well...I am knocking on my desk.
The fluttering temp guage came from a broken wire on the sending unit connector, the fluctuating charge came from a series of bad grounds.
Main and secondary ground cables were replaced with 1 guage welding cable, and an additinal battery to block ground was installed. (also #1). using a marine style battery post clamp.
Several of the ground connections around the car, especially on the engine block where the connectors were very corroded were replaced with zinc plated copper ring terminals and silver soldered, not crimped.
Now the guages read correctly, with only a slight dip in the voltmeter when brake lights come on.
Even with all lights (h-4's), A/C and stereo on the guages stay steady.
The main ground cable was corroded almost a foot up its length, and the insulation was brittle and cracked.
I assume this situation is fairly common on cars of this vintage because of the high underhood heat and so forth.
Wire resistance increases with age, causing voltage drops at accessories and at guages.
The fluttering temp guage came from a broken wire on the sending unit connector, the fluctuating charge came from a series of bad grounds.
Main and secondary ground cables were replaced with 1 guage welding cable, and an additinal battery to block ground was installed. (also #1). using a marine style battery post clamp.
Several of the ground connections around the car, especially on the engine block where the connectors were very corroded were replaced with zinc plated copper ring terminals and silver soldered, not crimped.
Now the guages read correctly, with only a slight dip in the voltmeter when brake lights come on.
Even with all lights (h-4's), A/C and stereo on the guages stay steady.
The main ground cable was corroded almost a foot up its length, and the insulation was brittle and cracked.
I assume this situation is fairly common on cars of this vintage because of the high underhood heat and so forth.
Wire resistance increases with age, causing voltage drops at accessories and at guages.
06-07-2001, 10:18 PM
#2
Nordschleife Master
Good job. 
Now you see how that corrosion creep up the wire can go nuts.
I don't know if you sealed the terminal ends, but you may wish to as they are fresh. There are specific terminal products for this but a simple way is to go get some GE II Silicone sealant and heat shrink tube. Slap the silicone on the terminal end opening (where the end of the wire sticks out) and wire insulation joint. Slip the heat shrink over and shrink, wipe up the silicone that squeezes out. That wire will last forever even in a salt water enviroment.
Your next wiring project should be the forward lights. You can get a pretty dramatic improvement in performance for not much in out of pocket costs. Nothing else on the car is as voltage sensitive as the lights. Your perfect target up there is 13.5 volts when they are on. At 12.8v you are down to 83%. 12.2v it's 67%.
As an aside, given you made the upgrade in primary/secondary battery ground with a monster #1 gauge, that additional new supplemental engine block ground would do you a whole lot more good going from the block to the forward frame lighting grounds rather than battery. They are on the frame by the headlight buckets.
Now you see how that corrosion creep up the wire can go nuts. I don't know if you sealed the terminal ends, but you may wish to as they are fresh. There are specific terminal products for this but a simple way is to go get some GE II Silicone sealant and heat shrink tube. Slap the silicone on the terminal end opening (where the end of the wire sticks out) and wire insulation joint. Slip the heat shrink over and shrink, wipe up the silicone that squeezes out. That wire will last forever even in a salt water enviroment.
Your next wiring project should be the forward lights. You can get a pretty dramatic improvement in performance for not much in out of pocket costs. Nothing else on the car is as voltage sensitive as the lights. Your perfect target up there is 13.5 volts when they are on. At 12.8v you are down to 83%. 12.2v it's 67%.
As an aside, given you made the upgrade in primary/secondary battery ground with a monster #1 gauge, that additional new supplemental engine block ground would do you a whole lot more good going from the block to the forward frame lighting grounds rather than battery. They are on the frame by the headlight buckets.