Headlights

Hey there. I can find a wiring diagram on this but nothing that shows me the internals (Coils/contacts) of the isolation relay and individual headlight relays. I'm chasing a strange fault.


History:

The 84 I bought had the motors disconnected, so now it's time to get the headlights working again.

Symptoms, first problem:

I found the car with both motors disconnected at the headlight relays.

I plugged in the drivers side motor at the and the motor spun continuously. I changed that motor with a spare I have and that fixed this side.

So the first problem is fixed.

The other motor runs ok when plugged in.

Symptoms, second problem:

So, now the trick is that the headlights will go up, and will sometimes go down. Sometimes when I turn the switch off, the lights hang up, and the lights themselves dim, but do not extinguish. The voltage on the yellow wire (Main output to the headlights) dropped to 8V from 12V with the switch off. I checked the grounds and they are ok. It is definatley a +12 source issue.

I suspected that the switch is faulty (Leaking +12V), so I changed it with another I have. The same fault happened, again intermittently.

So, I figured I have two bad switches. I took one apart and it looked ok, and tested out fine with an ohm meter.

The one wire which I'm not sure of the function of is the white wire. It is +12 from the switch when in the off position, and open circuit (0V) when the headlight switch is on. It goes to the isolation relay. If I jumper this wire to a solid +12, I can't make the headlights screw up. They work great. So what is the white wire for???

Its obviously switched for a reason, but I can't figure it out without more info.

Any insight greatly appreciated.

Thanks,

Chay

I'll try to find my 'good' diagram, but in the mean time...

There's a diode in the isolation relay.  Seen it go bad many times.  Looks like a 1N914 or similar.

Pop the tops on all 3 of them, and file the points.  They're pretty exposed to the weather.

Thinking a little more, you may be onto something there.

The lights won't come up without the white being powered up. The lights go on and there is an audible click (The iso relay turning on) however.

That would tend to implicate the diode as well, or the contact on the cathode side of the diode.

Thanks again,

Chay

There's a couple of small tabs there.  Just get two really thin screwdrivers under the edges and pry out a tiny bit.  It'll drop right out sometimes.  Sometimes you have to tug it out, if they used a lot of the black goop.

Here's a color version of your pic (for anyone else who finds it easier):

Works great! Saaawweeet.


Thanks again,

Chay