Chevy Nova Forum banner

1 - 7 of 7 Posts

·
Premium Member
Joined
·
402 Posts
Discussion Starter #1
Need some help here. Not good with electrical.

I hooked up an aux fan on front of radiator to help cool since it has been about 178degrees everyday this summer. I hooked the hot to a switch under dash then to a male spade on the fuse block that was hot all the time. The ground went to a bolt on the radiator support cradle. Everything was fine and worked good. we went to some event and I turned the lights on while coming back one evening and nothing. Weird. I parked at the hotel and went in. The next morning we went back to fairgrounds and everything still worked except the headlights. It was sunny, move on. I turned them on later and one came on. Turned them off and back on and nothing. Went home and put it away until today.

Disconnected fan wires from fuse block and ground and checked it. Still no headlights. If I pull halfway, taillights and park lights are on. Pull all the way on and park lights turn off, no headlights, but taillights stay on.

All fuses are good. I thought a hi/lo beam floor switch but thought that would not impact the parking lights but. I could be wrong.

Thoughts? Thanks in advance.

Cale
 

·
Registered
Joined
·
7,041 Posts
dimmer switch has nothing to do with park or tail lamps.
its where i would start.did you try rapidly clicking it several times while someone watched headlamps? it could be a freek thing that both headlamps are toast but doubtful
 

·
Premium Member
Joined
·
402 Posts
Discussion Starter #4
I have not yet checked power to the headlights and will check. I would think even if they were burned out, the parking lamps (amber lights below headlights) would still work.

Cale
 

·
Registered
Joined
·
1,196 Posts
If you havent already, download the wire diagrams for your nova.

You said you were not fantastic with electrical, so Ill explain some stuff in a bit of detail, dont know how much you know....

Take a mulitmeter (volt meter) and probe the headlight circuit for power. If you said the fuses were all good, I would back probe the circuit.

Backprobing simply means, taking a meter, and PROBING a section of wire, to see if it is doing what it is supposed to. EXAMPLE: a tail light does not work. If you test the socket, and it does not have 12 volts, you know the problem is upstream somewhere, closer to the fusebox, battery etc. If you go test for power at the fusebox, and find 12v...that means your problem is somewhere down stream on its way to the light socket. Backprobing gives you an idea where you need to isolate the problem.

I would start by testing the engine bay harness to check the front lights.

BACKPROBING THE HEADLAMP ENGINE HARNESS
To do this open the hood and look at the two plugs (Im thinking first gen, sorry if yours is not the same) coming out of the fire wall. One runs up and over the the passenger side to power your starter, distributor and coil (Again, sorry, I have an inline) and the other plug has a harness that leads to the front of the car to power the horns, headlights, marker lamps etc. This is the harness that powers your headlights, and it needs to be checked to see that it is getting power from the fusebox. These two plugs are connected to the fuse box from the back I believe.

One of those wires sticking out of the plug should be BLACK/LT. GREEN (black with a light green stripe) and there should also be a TAN wire. These two wires run from your beam selector switch to the headlamps, providing power to the appropriate beam, high or low.

You need to set your meter to volts, (always set a meter for HIGHER than the max voltage your trying to measure. If your measuring 12, for example, use either 20 or 50.)

Place the black lead of the meter on a good body ground, (engine bolt, sheetmetal screw, negative battery terminal...) and hold it there. With the red lead from the meter, your going to try to stick it in the back of the plug with it connected to the correct wire (BLACK/LT. GREEN or TAN) and your looking for 12V. You cannot unplug these, because one of them powers the whole car. Disconnect it and the car is dead. (Do not remember if its one or both...)

If you need to get a sewing needle or a t pin to stick in the back of the plug, and then touch the meter to that, that works ok too. But you need to see if that plug is receiving current from the fuse block.

HEADLIGHT HARNESS GROUND CHECK
To do this, take the driver headlight out if you have to (not sure) and get to the headlamp plug that connects to the bulb. It should have slots for three prongs. One slot should be a ground (BLACK). Check that it has continuity with the body of the car or the battery by turning the meter to OHMS, and then putting one lead in the slot that the black wire connects to. If you cant tell try all three slots to see if any of them are grounded.

The headlamp curcuit looks like it grounds out on the driver side somewhere with a black wire screwed into the body. Locate and check that ground. It should be clean.

Then test the ground lead from the driver side headlight to the passenger side one. It is a little harness that should extend from the left to the right side of the car, tucked under the core support by your hood latch. Take the slot of the plug you determined was a ground for the left side, and stick the test meter lead inside. Do the same with the passenger headlight plug. Those two terminals in that plug should cave continuity, be 'connected' to eachother.

HEADLIGHT HARNESS POWER CHECK
After you make sure your grounds are good, I would test the plugs for power. The plugs have 3 leads, so one lead would be the ground (BLACK) the other two are your low and high beams. The power runs through the beam selector switch, and then through either the BLACK/LIGHT GREEN, or TAN wires to reach the headlights. Probe the headlight plugs with one lead of the meter, while the other lead is connected to a good ground.

When the headlights are on, you should have power to either one or the other of those two wires, depending on the beam selector switch setting. Probe both plugs 2 times...one on each headlight setting. Each plug should have 12V both times, just in different slots.

Start there, (if your still having trouble) and let us know. If the fuses are good I would check the ground first, just to be safe, and then start probing for power, first at the plugs on the firewall, and then out to the harness plugs that connect to the headlights.

Hope it helps and if any of you guys can add to this or correct me on an error I may have missed, Id appreciate it. I was looking at the diagram for wire colors and routing, and referring to a 64 (mine).

If your stuck stuck, PM me and Ill see if I can get on the phone and walk you through the steps. I wouldnt wanna read all that crap I just wrote:no:

GOOD LUCK!!!!!!!!
 

·
Premium Member
Joined
·
402 Posts
Discussion Starter #7
Thank you for the very detailed instructions. That was very helpful.

Turns out it was a bad ground. That fixed, I am back on the horse.

Thank you again.
 
1 - 7 of 7 Posts
Top