OK, here we go - I have been beating my head against the wall on this one I have replaced all the wiring harnesses on my 65. I also replaced the headlight switch. The dash lights are dim and when I hit the headlight door open switch, the dash lights blow a fuse. How is this related to the dash lights? They're not even on the same circuit Any ideas?

Thanks,

Bob

 

Bob you're right in that they are on different circuits which is very strange. I am assuming that you are saying that the 4A fuse is the one blowing which makes it harder still since it's downstream from the headlight switch (easy first culprit to suspect). The dash lights are not exactly max candlepower anyway but think that you have been around long enough to know normal from dim. On the lower right side of the fuse block are two spades labled ACC and LPS. The voltage to those is controlled by the dimmer control of the light switch so you can actually measure what is going on when you turn the headlight switch to brighten or dim the lights. Mine reads 2V just before it turns fully off clockwise. Fully counterclockwise just before it turns on the courtesy lights - it reads about 10.5V. What does yours read? I would think the only other way to hunt down the short is to isolate some things. Since it's the headlight opening switch - I would start there.

You could put the fuse back in, note that the dash lights are working and then crack open one or both of the headlights manually by hand. Open enough so that the headlight door open light comes on on the instrument panel. See if the fuse blows. If not, disconnect the headlight motors and hit the switch to open the lights. See if it's wiring or really the motor load that is blowing the fuse.

That would be where I would start.

Good luck.

Geek

 

That's a good one. Does the fuse still blow whether or not the parking/headlamps (dash) lamps are on?

My WAG without more info is that the headlamp assembly switch is bad or not wired up correctly, and that the instrument cluster ground is not connected properly or finding a ground. that way you divert power to the cluster housing with the assembly up/down switch.

Make sure you have the headlamp motors grounded. I have seen the ground lines for the motors left hanging and also connected to the header (steel) bar.

PS try unscrewing the switch from the cluster and put the lamp assemblies up/down with the switch hanging (not grounded to the cluster). If that works, the switch or its wiring are definitely screwy.

 

Thanks for the suggestions. I'm gonna try to isolate it by unplugging the headlight motors first. I can turn on the lights, hit the hi-beam and everything is cool altho very dim even with a new reostat headlight switch at max. As soon as I hit the headlight door open switch, there goes another fuse.

Could it be a ground problem with the dim instrument lights? All harnesses are new. Unfortunately the car is back together when all this started happening so I am doing a lot of standing on my head!

Thanks again,

Bob

 

yes

I'd suggest you try the wipers - since they rely on cluster ground - but the motor is hard to replace .

If the lack of a ground on the cluster is causing the dash lamp problem, IMO it has nothing to do with the fuse problem. Try unscrewing the headlamp assembly switch (see above). It doesn't require headstands.

 

Hey Bob,
You said that you put all new harnesses in the car? Engine harness, headlight harness, and dash harness. If you did all these harnesses, then go to the driver side of the firewall were the engine harnesses plug into the back of the fuse block. Unplug both plugs and see if any of the little electrical connector on the harness and on the back of the fuse block got bent when you plugged the harnesses up. I've seen funny things happen and it is just a bent prong. I hope it is this simple.
Dan

 

Electrical gremlins are THE biggest PITA to fix.....