62Jeff

About a month ago I posted about my 65 which had blown the dash light fuse on my maiden night trip after replacing all of the wiring and bulbs in my car. I had also replaced the headlight switch and had all of the instruments Oliverized. (rebuilt by Jason)

I received good advice on how to test things out if my car was reliably blowing fuses. Unfortunately, every time my car blows the dash light fuse, I come home and pop a new fuse in and find everything working fine. I've blown 3 fuses thus far.

Over the last few weeks I pulled the instrument cluster out and rerouted the wires, checked all the panel lamps for problems, and really didn't find anything of note other than one panel lamp bulb that was blown and cracked. I even jostled all the dash wiring while the lights were on in an attempt to make the fuse blow but to no avail.

Today on the way home from a buddies I decided to drive home with the lights on to see if I could make it all the way home without blowing my fuse. Nope. it blew within a few minutes.

So I get home, stick a new fuse in and the lights are working again.

After getting disgusted and coming in the house for a while, I had an idea and ran this simple test - go out to the garage, turn the headlights on, confirm the dash lights are on, then go back in the house to watch TV while the car sits there with the lights on. 20 minutes later I went out to the garage and the dash lights were out - the fuse had blown with the car just sitting there.

So what the heck does that mean?

Thanks,
Jeff

Edit 11-11-2006: If you wish to learn what the problem/solution is, you can skip directly to the answer here

Sky65

What size fuse are you using? From my diagram it looks like a 4 amp? Do you have a hand ammeter? I would remove the fuse and use the ammeter accross the fuse contacts. Turn the lights on and see how much current the lights draw. If it looks good maybe move the wiring around again and watch for fluctuations on the meter. Maybe you will catch a rise in the amp draw that is so quick it does not blow the fuse. Good luck.

62Jeff

It's a 4 amp fuse. Odd thing is the fuse blew after between 1 and 20 minutes of being on. After letting the car sit for a while, I put yet another new fuse in and turned the lights on. This time the fuse blew somewhere between 40 and 50 minutes later.

I'm wondering if I put the wrong bulb in one of the sockets and am drawing too much current. I got a bulb-kit from Lectic Limited but it was a bag-o-bulbs with markings that I could barely read so I easily could have grabbed a wrong bulb - as long as they all fit the same.

My car has A/C so I might also just unplug the separate wire for the A/C lights and then see if the fuse blows while the car sits there. That may tell me something about the amount of current.

I'll pull the fuse and check the Amps tomorrow with my multi-meter, but maybe tomorrow.

Donald #31176

Had a similar problem with the headlites on and blowing the dash lites. It was a defective headlite switch which shorted every so often.

62Jeff

Did you find this by wiggling the headlight switch ****?

Although the fuse blew today in under 20 minutes and over 40 minutes while sitting still in my garage, the fuse blew 3 times while on the road within minutes.

Donald #31176

When I turned on the headlites every so often the dash lite fuse would blow. The switch had a contact pole that broke loose.

babbah

Put the old headlght switch in temporarily and see if your problem countinues. IMO I dont think the instrument bulbs draw anywhere near 4amps.
Sounds like HL switch to me......

62Jeff

It's worth a shot. My dash lights didn't work at all before I replaced the wiring and headlight switch. I can pop the old switch in though to see what I find.

bweaver999

Did you get the head light switch from LL as well? I purchased my wiring and new switch from them in March time frame. Still have not figured out what is blowing my fuse yet either. Mine blows as soon as I turn on the lights. Unfortunately, the old switch is gone. Look forward to hearing about your fix!!

62Jeff

Nope, got the switch from Long Island Corvette Supply. I'll post whatever I find, and maybe I'll mess with it tomorrow. With factory A/C, it's not easy to swap out the headlight switch.

bweaver999

Just did a quick test, torned the inst lights off, replaced the fuse. It blew as soon as I turned on the cluster lights. Not a great test, probably need to disconnect the feed wire and jump it to bypass the switch. Looks like the DG wire supplys the cluster lamps.

62Jeff

That sounds like a direct short. I wonder, if you removed the fuse, then checked for a short between each fuse connector and ground, what would you find? If you found a short at one of the fuse connections would that indicate your headlight switch is bad? If you found a short at the other fuse connector would that mean one of your gray-wires is touching metal?

Helpful threads that have come up thus far on this topic...

JohnZ posted this in response to another's dash light problems
http://forums.corvetteforum.com/show...5&postcount=14

MagicV8 posted this in response to my original query when this problem first came up for me. At the time I installed a new fuse and my lights came on, so I thought my problem had been solved
http://forums.corvetteforum.com/show...43&postcount=5

bweaver999

Magic is the man!!!! I have 1 ohm measuring between the lamp side of the fuse and ground. I tore the cluster apart, figured pull the lamps one at a time and see when it went to 3.5 ohms. When checking lamps near the headlight switch, noticed a jump to 2.5 ohms. Believe it is something in the switch connector but can't figure out how to remove the switch, actually the ****. Wiggling the wires, I can get it to jump from 0.5 to 4 ohms. Shouldn't there be a "spring" coming out of the **** end to hold it on the shaft? Is it hidden inside the ****?

62Jeff

Pull the normal light switch **** out as far as it will go. Next, on the bottom of the switch is a little spring loaded button - push that in and hold it, then pull the light switch **** out the rest of the way.

With that out, you'll see a little nut in the front of the instrument cluster with 2 slots in it, where the headlight **** had been. Unscrew that special nut and then you can remove the switch from the cluster.

bweaver999

Thanks!!!!!!!!!!!!!! I am in the area now. Know it's not the switch, does not appear to be the connector either. Moving the bundle around makes the ohmmeter jump around. Probably take another look tomorrow night. Will post what I find.

Do I need to press the "button" to re-install the shaft or just push it in the switch?

62Jeff

Typically no, just push the **** shaft into the switch, you should hear a subtle click as it snaps back in place.

Dennis Beck

Jeff,
Have you tried your experiment by just turning on the lights to the parking light position without going all the way to full headlights?

62Jeff

No I have not, I'll give that a try when I get home from work this evening.

62Jeff

Dennis,
Tonight I tried your suggestion, turned the lights just to the parking light position. After 10 minutes the dash lights were still lit, so I left the garage to watch TV. After 50 minutes I checked on the car and the fuse had blown again. It must have blown relatively close to the 50 minute mark because the instrument cluster was still warm to the touch.

Jeff

magicv8

I=E*R (current equals voltage times resistance) or as Ohm would say (if he were alive today), when the alternator is turning E=14volts and the R due to the bulbs isn't changing, the I with the car running is larger than the I (current) with only the 12volt battery supplying the E (electromotive force).

Aside from a marginal circuit, the obvious possibilities are that the wiring is shorting somewhere occasionally, or the alternator is exceeding 14 volts - but that shouldn't be the case if the fuse will pop with the engine off.

Ohm's law says the system is marginal (effected by higher alternator voltage) and the higher alternator voltage is driving the current high enough to blow the fuse sooner than a 12volt battery.

NOTE: 9amps is the load limit of the 20 gauge wire that powers the bulb socket wire splice from the fuse holder. Stay under it.