Hi folks...need your help.
Took the wife out for a "spirited" ride in the 64 Fri night. After a rather hard departure from a stop light, all my dash lights went out. Apparently the tail lights went out too. Courtesy lights and brake lights still function. I found a blown fuse so replaced it and it immediately blew. Did this three more times. I watched it blow the second time and the third time while pushing the fuse into the clips. Drove home with no fuse and certainly don't want a fire so need your thoughts please? If you've ever seen this before or even something like it (red wire issue or bad /corroded fuse panel ?) I'm all ears. Thanks in advance!

 

My guess is that it is in the tail lights. With the lights turned off does the fuse blow?

Dom

 

Yes, fuse blew again with lights off.

 

Sounds like a short to ground in whatever circuit is protected by that fuse. Which fuse was it? I believe the taillamps and dash lights are protected by different fuses. Brake and courtesy lights are fused together on yet another circuit. The fuse panel identifies the circuits.

 

If I remember GM had the dash lights and tail lights on the same circuit so if you lost dash lights you know that you do not have tail lights.
So fuse blew with lights off, not as easy. this points to the dash lights, if the do share the same circuit? Possible light switch?

Dom

 

I will test it all again tonight and verify the fuse location.

 

I do not believe this is true. The tail lights have a separate fuse and when you turn them on power is sent to the tail lights and then to a separate fuse in the panel and then to the dash lights.
So if you have no dash lights you can still have tail lights but if you have no tail lights you can not have dash lights, providing all the bulbs are not burnt out.
What fuse is blowing and does it blow if you do not have the light switch pulled out?

 

A couple of half correct points on the tail/instrument lights. The tail light fuse (10 amp) covers both the tail lights and the instrument lights. If the tail light fuse blows, the instrument lights will go out as well. The instrument light fuse (3 amp) covers only the instrument lights, but it gets power through the tail light fuse. Both circuits get power from the headlight switch. It's not likely to be "the red wire." Thats on the engine harness side of the fuse block connector.

Fuse blowing with all lights off? You may have something bad in the fuse block itself. The tail light circuit is supposed to be cold when all lights are off.

 

That answer wasn't very helpful. Try this along with whatever else you try. The rear body harness connector is somewhere in the vicinity of the driver side kick panel. Worst cae, pull that panel to expose the connector. Disconnect it and try a replacement tail light fuse. I'm betting nothing happens. You may find the power wire to the tail lights is shorted to ground somewhere along the way to the light sockets themselves. Check it from the connector with a test light or ohmmeter. It's an 18 gauge brown wire. If that circuit shows open, then go back to the switch. If the tail light circuit is shorted, then start pulling tail light bulbs. If the circuit still shows a short, then reach behind the valance panel and start pulling the tail light pigtails out. They just twist a quarter turn or so. Make sure the contact buttons aren't touching anything and try the circuit test again. Pull the license plate light as well because it''s on the same circuit. If you still show a short circuit, then the trouble is in the harness itself. Could be pinched or broken insulation, more likely than not between the tail lights and where the harness exits the interior - on convertibles its behind the driver side deck lid spring, under the carpet

You can also try pulling the instrument light fuse to see if the problem is in that circuit. It may be possible to blow the tail light fuse and not the instrument fuse. Unlikely but possible.

 

Thanks for all the replies. Didn't get the chance to look at her again last night but have some direction at this point. Will definitely post back what I come up with .
Cheers,
-Phillip

 

I don't understand it...I just replaced the fuse again (2nd fuse from the bottom). Didn't blow this time (with lights on or off). Brake/parking/headlights still work. Dash and courtesy lights work (courtesy lights never quit). Going to have to take her for a drive and see if that makes any difference again (blew initially while I was driving then two more while parked). Since it really did happen and there's no logical (to me) reason to now work, I expect I will still be testing wires. Will keep an update.
Cheers,
-Phillip

 

Long shot, but if the car has a radio, there are capacitors on the ammeter, brake switch, and other devices, not sure about the headlight switch. I had one deteriorated and the lead came out of the cap and was shorting to ground. Maybe some of the others with the right schematic can tell you where they are located.
You don't need the capacitors if you are running an aftermarket radio or don't listen to AM or have resistor plugs and wires.
Long shot, but might be worth a look.

 

Interesting you say that R66. Looked behind the instrument cluster and there doesn't seem to be any capacitors. Car does have an aftermarket radio, etc. However... when I press the brakes the radio produces nothing more than static until I let off.

 

Possible short in brake light switch . . disconnect the brake light switch and see if your problem goes away.

 

Though not the blown fuse problem, I switched out taillight bulbs in case they were somehow shorting (from LED back to incandescent 1157's). Still have taillights and brake lights. For grins, turned on radio and radio static went away. All the sockets and bulbs were good so doesn't appear to be a short back there but the LEDs must be providing some sort of radio interference. Anyway, still looking for a short or something before she blows a fuse again. Since I was getting on it hard when she initially blew, I'm leaning to some kind of short but don't know where. The short must've still been present when I pulled over a few blocks later and tried to reinstall a fuse, causing them to repeatedly blow (pretty sure the light switch was on but may have been off). Then on the subsequent drive home, the suspect short cleared itself and thus now she's no longer blowing the fuse. Seem logical? It would seem to me the rear harness is the likely culprit but may be a corroded fuse block or even something in the wiring behind the dash?
- Phillip

 

LEDs react differently than incandescent bulbs and are difficult to use in the same circuit. I put in infused LED tail/stop lights and then added a third LED brake light on the circuit off of the brake switch in parallel circuits. I found I lost the brake lights in the tail/stop LEDs after adding the third LED light. I am going to try the third brake light in series.
Also, the LEDs are polarity sensitive. Maybe one of the electrical engineers on the forum can explain the reason, but it could be the LEDs are contributing to your blown fuse. Did the problem start after changes to the electrical system, e.g., changing bulbs, adding radio, etc.?

 

I agree with R66 . . could be the LED change is your problem . . some LEDs can short internally and may not be designed for our cars.

 

Also some of the cheaper LEDs can have loose solder joints which can cause intermittent problems.

 

She had the radio when I got her. I added the LED 1157's. Reason was, the 2nd owner had done a 6-taillight modification in the late 60's and apparently was blowing the 10amp fuse. He told me he "thought" the extra wattage overloaded the fuse so he had a 15amp in there. Apparently this worked fine for the limited miles and whatever style of driving he did the next 40 odd years. This concerned me due to the age of the wiring so I tried to simplistically lower the amps by putting LEDs in and having less draw. All seemed to be just fine until last weekend when the fuse blew. But...when it did blow the 10 I had back in there, I only had an assortment kit box of fuses with me. I put another 10 in and it blew right off the bat on the side of the road. I put a 20 right behind it (because that was all I had next) in and it also blew. This was the scary part as I had doubled the size of the fuse and it also blew so I removed the fuse altogether and drove home with only brake lights (no dash lights either). Now, all seems to be working fine and that is also the strange/scary part as I have done nothing from a "find/fix/repair" perspective. Dash lights all work, exterior lights all work, 3 interior lights and glove box light all work. Clock and clock light(s) do not work ...probably the bulb and clock is shot. As told, corvette america installed the radio years ago at a show. Interestingly, radio (digital am/fm/cassette) totally resets each time the car is off/locked. Learned this the hard way by shutting the car down once in the garage and leaving the ignition off but not locked only to have the battery eventually go dead on me. Don't wand to add more to the mix here. That's probably another to do item, just thought I'd share. Focus at the moment is the blowing fuse. Electrical gremlins be damned!

 

Blowing a 20 amp fuse, I would be surprised if there is not some sort of arc chard insulation on the wiring or arc to ground some where. A good visual inspection of all wiring in the circuit may find your problem.
If you disconnect the body connector at the drivers side kick panel and remove all bulbs, then use your VOM ohm meter with an extension jumper wire to test each wire going to the rear panel, you may find which one is shorted to ground if in the rear body harness. Pull and shake the wiring where it is free see if it grounds.
With the harness disconnected, you could then use the VOM or a test light to determine the current flow across the fuse or try another fuse to see if it blows.
Then study the schematic and trace the wiring to the light switch and back to the fuse box. Test the wiring with the VOM with the battery disconnected or fuse removed to see if there is a ground.
An intermittent short indicates a switch problem to me, I would remove the light switch and look for visual heating evidence of the switch and connector and test the switch with a VOM and / or test light.
I have to plead guilty of ignorance when it comes to LED bulbs, but my guess is you should be able to check each with the VOM to an open circuit, and a short between the two filaments.
Hopefully one of the electrical engineer will correct me if I am wrong and provide you with better guidance.