Thanks to GeorgeK who started this thread way back in 2003 and all who have added their comments. I just finished adding a 3A mini fuse to this circuit. Way easier than I expected and well worth the investment in time for the piece of mind. As others have noted, after disconnecting battery and unscrewing plastic retaining nut, you can wiggle the switch out and down to gain very good access to the terminals. Only issue for me was that the retaining nut for the switch was cracked. Put it back together with some fiberglass resin and now back in business. One more electrical worry I’m crossing off my list.

I laughed when I saw this post come up. Funny...I have this bookmarked and on my schedule to add the 3A fuse today. Such an easy mod. I have recommended it many times (for over 20 years).

Sadly, I had the underdash smoke check and my headlight switch burned up Thursday night. Ka-ching...there goes a quick $400 (switch already ordered) and a few hours work double checking all related wiring for want of 10 minutes and a $10 part. Luckily, it appears (so far) there was no damage to my harness that I would have to repair...but found lots of "while I am in there things to do). Had this car for many years and had put off adding the fuse. Karma.

Let me recommend once again...do this easy mod.

Sorry for the bad luck. What bought the failure on?

Yeah I have had this thread saved for years and still haven't done it. I have what I need to do it just need to get it done. Maybe this will be a good thing to check off the list tomorrow. Sorry to hear your headlight switch burned up.

Not sure...but was messing with the heater/ventilation panel when it happened...so likely related (since the lights on the back of the panel are some of the unfused circuits). I had just replaced some bulbs and fixed the light that comes on when the fan comes on (previous owner had cut when they pulled the radio apparently). Everything was working and I was putting it all back.

Since I could not find the problem under the dash (other than a melted switch), I am also pulling the ventilation system (while I wait on a switch) to examine it better and so I can see the back of the firewall for damage to any wiring back there. I can get that perfect while I am in there.

Also karma...in my stash, I had a spare for every switch in the car but that one for the headlights... Guess I will put the Sucro headlight relays from my other car (found it looking through my parts for the headlight switch) in while I am at it.

Should have disconnected the battery...but had done that work many times without error. Since I had the frunk open, I did quickly grab a wrench and disconnect the positive terminal which may have reduced the damage. I usually leave it hooked up when fixing bullbs...as it saves a step or two when testing them. Bad call this time I guess.

Thanks! Oh well. Taught me a lesson (order priorities a bit better). At least I am very comfortable with fixing it...had a couple of these '74s...and have done most tasks at least once.

I'm also in the "I wish I had installed the fuse earlier" camp. I managed to short my dashboard lighting loom (I removed the steering column to put in new bearings and crushed one of the wires under a washer...), and let me tell you, it is a lot of work to open up the wiring loom to inspect and remove the burnt wire, and retape the loom. So in hindsight, 10$ and 5 minutes of work is a no brainer.

Bumping this one up for thoes who havn't done it and need to do it tomorrow. (Me).
Thankfully, no issues with my 79 coupe.

anyone know off hand what gauge the dash wiring is? 18 AWG?

Found it in the threa, 14-16 AWG

Doing some troubleshooting and had a related question:

How much voltage drop should I expect across wiring connected to gauges? e.g. Switches and related wiring from battery to gauge and then subsequently from the gauge to ground?

With the car running and battery voltage at the battery measured at 13.8V, I am only measuring ~12.6V from power to ground on my oil pressure and oil temp gauges, so I am dropping ~1.2V somewhere else in the circuit(s) and I'm wondering if that is normal.

Why I'm asking: I recently added a voltmeter to the aforementioned gauge and it's only displaying ~12.6V, which is obviously nowhere close to the true battery voltage. A loss of 1.2V on the rest of the circuit seems excessive, no?

Yes, 1.2v drop is excessive if that's on all circuits. Your volt gauge should show full voltage. If it doesn't, are you sure you connected it directly to a "hot" wire and a solid ground? Is the gauge accurate? (test it directly across the battery)

However, on your gauges, remember, the senders have resistance too. I don't know what that is offhand, but the voltage will be split proportionally across two resistances in series.

http://forums.pelicanparts.com/uploa...1678853855.jpg


I cant get this retaining nut to turn. Any suggestions??





1985 Carrera coupe M491

Take something like a needle nose pliers or a snap ring pliers and insert the ends into 2 of the holes and twist to unscrew. You’ll get better leverage that way. Once it starts to turn you’re fine, it’s just that initial breaking loose 35 years of dirt that you need to overcome.

Remove bezel with pick tool or snap ring pliers.
Remove washer with pick tool.
http://forums.pelicanparts.com/uploa...1578619815.jpg

Thank you. Ive been cranking on it w snap ring pliers.

They fit good, except Ive got 2 of the holes mildly damaged from turning so hard.
I sprayed around it w silicone & WD40, seperately. To no avail.

Its the initial 'breaking loose' that i require... ?

I too fused from 58a and added a LED supported dimmer since the OEM dimmer will not work with LEDs

Hmm, that seems odd. I wouldn't think it should take THAT much force to free it.

Maybe shock the snap ring pliers with a hammer it?

This rosette is still available from our host:
https://www.pelicanparts.com/More_Info/91161321307.htm?pn=911-613-213-07-OEM

So don't worry too much about damaging the one that's in there because you can still get it.

silly question...rotating the correct direction?

Fair question. Tho totally possible.
I once left a plastic cap on a battery post. Doh

Lefty loosey? im turning counter clockwise, as i view it.

Thanks