fgcox1

Been through the threads on electrical on this board and others, haven't found anything on this.

86 base.

Headlight relay is arcing. Also causes what sounds like arcing in the switch. Cluster lights only are out (may be coincidental). Lighter works fine as do radio, equalizer, logicon.

Took case off of relay to verify arcing. Is arcing and contact appears to be opening and closing really fast. Can hold the contact closed and headlights brighten.

Went through the following:
Checked voltages and grounds at switch...all ok
Used Simpson 260 Analog VOM to go through grounding system <2 ohms anywhere. (Motor, coils, body, starter, interior grounds) Checked grounds at headlight connector, OK. Voltage appears ok at connector with switch on.

Replaced headlight relay with new, still arcs. When holding the contact closed the headlights brighten significantly.

Have tried different light switch just in case but same results. Also did Headlight Switch Relay mod in hopes it might solve but it doesn't, same symptoms.

At this point I am open to ideas. I have the factory wiring guide and have used it to follow but it hasn't triggered anything that has helped.

Really appreciate any help.

Tnx Fred

HAILERS

Pull the plug (14 pin plug), off the light switch located in the cluster. What happes when you put a ground on the RW (red/white) wire with the plug disconnected? Still chatter? What happens if you maintain that ground and disconnect the 10pin plug on the cluster?

fgcox1

More info.

Grounded the wire as suggested, no arcing. Haven't been able to get to the cluster to remove the other plug. (delayed due to death in the family)

Took an additional known good switch and tried it, same-same problem.

One interesting thing I noticed is when this is occuring the up/down switch works but the headlight on off doesn't move the headlights PLUS, the headlights are on all of the time, no matter what switch position.

I checked continuity between the RW at the switch and the WL at the relay and it is ok. (My wiring diagram shows them changing color at X-17) I plugged everything back in and got on the back of the 14 pin plug to see what was happening on the RW when everything is hooked up and it shows about +9VDC. Doesn't seem to make much sense. What is switched out the RW? I assumed ground since you can ground it and they work. Is this floated somewhere above ground?

Noticed your in FW. If you want to send me your number or I can give you mine we can go over on the phone.

Tnx Fred

Nick86

iTrader: (1)

I had the exact same problem.

The switch would buzz - and the relay would click constantly. I replaced the relay AND switch multiple times to no avail. But the last thing I replaced fixed it:

You need to replace the short wiring harnass that plugs into the light switch. It's about a foot long and goes from the switch to a connector under the dash. I tested mine - and thought it to be ok. Then I replaced it with another one and the problem has vanished.



While you are at it, do the relay mod to avoid this happening again!

fgcox1

Where did you get the replacement harness? Used (Ebay) or can you get it new. Hate to see what the stealership will charge!

Tnx Fred

fgcox1

I chased throught the wires in the harness and they all look ok. (ie: continuity and no shorts to other pins)

Anyone in the DFW area have a 86-88 headlight switch harness spare I could use to temporarily replace for troubleshooting?

I really am hesitant to buy one until I'm sure it fixes the problem.

Any help greatly appreciated!

Tnx Fred