Electrical issue

[tmontes]

I'm hoping someone can help on this issue. I have a 1972 Chevy truck. The truck had been running without any issues. Drove it out of the garage, cleaned it and tried to turn it on and would not. Is there a quick way to find a short. I have placed a check light from the ground on the battery and to the frame and it turns on then slowly turns off. So it seems that there is power to the frame but why does it turn off within seconds.

I have a short and can not find it.

I have checked all of the wires and found that the wires are not touching the body or out of place. But I have this issue. Before the short if I put on the brakes the front signal light would come on. Now that I have a short this happens when I put on the marker lights all of the marker lights turn on along with the signal lights and plate lights. When I pull the switch completely out to turn on the headlights the signal lights turn off and the right side marker also. I have replaced the switch and the flasher and it still has the problem and I have disconnected the turn signal switch to see if the that switch is the problem and it still has the problem.

[daveo68]

Sounds like you have a ground problem. I had one time and was one of the wires in taillight assembly. Took three days to find !!

[LockDoc]

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with Dave. Make sure you have a ground from the engine to the frame (should be down by the fuel pump), engine to the cab (should be on both sides on the back of the heads), frame to bed (should be on the drivers side behind the axle), both sides of the radiator on the core support (take them off and clean them good). If the ground straps are there in those locations take them off and clean both ends. If the are not there add them.

Oh, and welcome to the board....

LockDoc

[tmontes]

Yes I did check all of that and they are all there. I'm trying to figure out why if I pull on the switch for the markers they all turn on and when I pull it out completely just the signal lights and the right front marker turns off?

[LockDoc]

Originally Posted by tmontes

Yes I did check all of that and they are all there. I'm trying to figure out why if I pull on the switch for the markers they all turn on and when I pull it out completely just the signal lights and the right front marker turns off?

That is what bad grounds do.... Cause lights to turn off and on with no apparent reason. What happens when you turn the park lights and/or lights on then turn on the turn signals?

LockDoc

[tmontes]

nothing.

I followed the wires to check for cut, but nothing. The signals do not work at all. So I unplugged the signal switch and it still does the same thing.

[VetteVet]

Originally Posted by tmontes

I'm hoping someone can help on this issue. I have a 1972 Chevy truck. The truck had been running without any issues. Drove it out of the garage, cleaned it and tried to turn it on and would not. Is there a quick way to find a short. I have placed a check light from the ground on the battery and to the frame and it turns on then slowly turns off. So it seems that there is power to the frame but why does it turn off within seconds.

I have a short and can not find it.

One of my pet peeves is when some one calls a poor connection or a bad ground a "short". In electrical circuits a short is short (pun intended) for a short circuit. Which means a direct flow of electricity between positive and negative. A good example of this is when the main starter cable touches the header pipe and the insulation gets burned off until the wire touches the header. A short will blow fuses and let the smoke out of the wires. , but a bad ground will just cause stuff not to work.

What you have is what Dave and Doc said, a poor connection between negative and ground

I have checked all of the wires and found that the wires are not touching the body or out of place. But I have this issue. Before the short if I put on the brakes the front signal light would come on. Now that I have a short this happens when I put on the marker lights all of the marker lights turn on along with the signal lights and plate lights. When I pull the switch completely out to turn on the headlights the signal lights turn off and the right side marker also. I have replaced the switch and the flasher and it still has the problem and I have disconnected the turn signal switch to see if the that switch is the problem and it still has the problem.

Electricity has the same properties as hydraulics. It will flow in the path of least resistance. A poor connection or bad ground is resistance. When you turn on your headlights the current flows to the lights because you have a resistance in one of the marker or turn lights, probably a bad ground. Clean all the sockets and their mounts.

A good example of this is when one headlight is bright and the other is dim. The dim light has a bad ground, so more of the current goes to the light with the good ground or least resistance.

Originally Posted by tmontes

Yes I did check all of that and they are all there. I'm trying to figure out why if I pull on the switch for the markers they all turn on and when I pull it out completely just the signal lights and the right front marker turns off?

See above



I followed the wires to check for cut, but nothing. The signals do not work at all. So I unplugged the signal switch and it still does the same thing.[/QUOTE]


The turn signals and the brake lights run through the turn signal switch so if you disconnect it then they are not going to work.
The parking lights tail lights and dash lights are run through the headlight switch .