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Old 09-21-2005, 10:49 AM
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Keeps Blowing Fuse

I've been here for a while but never posted. This has been a great site and helped me many times! I'm having a problem with my dads 1946 Chevy coupe blowing a fuse. Here's the problem, I went to pull it into our shop the other night and it almost died then the gauge lights stopped working along with the dome light, park lights, tail lights, and brake lights. The head lights and turn signals still work. I found the blown fuse (It has glass fuses if this matters) and replaced it. The dome light worked fine until I turned on the park lights, then the fuse blew almost instantly. I looked for bare wires or something that didn't look right but nothing caught my attention. This is the first time the car has ever did anything like this in the 4 years we have had the car. So what should I look for? Thanks for the help.

hotrod48

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Old 09-21-2005, 11:17 AM
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Check the bulb sockets....chances are one of them is shorted out.
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Old 09-21-2005, 12:56 PM
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Okay, thanks.

hotrod48
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Old 09-21-2005, 01:30 PM
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A way of finding the problem is to remove the light bulbs that are easy to get to replace the blown fuse,Then switch the lights on and fit the bulbs back in one buy one until the fuse blows then you have found the area where the fault is or the wires are at fault
good luck stuart
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Old 09-21-2005, 05:21 PM
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First off I found out the radio doesn't work. Thought that was my culprit. It had the power wire pinched by the cowl vent mechanism. Unplugged, still didn't fix it. So I took all of the gauge light bulbs out, tried it, still blew a fuse. So I started looking at the headlight switch. On the plug that goes to it, was melted by one wire. I found a wiring diagram and found this wire to be "Dimmer power". The "Dimmer power" prong is also loose (I'm able to wiggle it). It has a later model Gm tilt column. So would my problem be in the headlight switch or the dimmer switch or neither? Thank you for your help once again, it is slowly helping me track down my problem. Thank you.

hotrod48
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Old 09-21-2005, 06:53 PM
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HotRod 48 tell us more about the vehicle.

You say 46 chevy coupe and tilt column. So we dont know if its a original car with a tilt column or one with a total rewire and 12 volt updates.
V8? What kind of wiring? 12 volt? etc, etc.

By the way a loose connection will cause heat and the melting you refer too. So all connections must be tight. The more current the device draws the more critical.


Where is the fuse? In a panel or feedline?

Rich
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Old 09-21-2005, 07:10 PM
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It has been hotroded. It has a 4.3 liter V-6. I don't know the year or model of the tilt column. All of the wiring was done by the previous owner and it looks like a homemade job. It is a 12 volt car. If it were up me, a total rewire would be in plan, but it is my dad's car.

I know a loose connection will cause heat, but with a factory connector is it possible (I know anything is possible, but theoretically).

The fuse is in the panel. The fuse panel is for glass fuses (One reason I want to rewire it).

If any more info is needed let me know. Thanks again for the help.

hotrod48
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Old 09-22-2005, 02:22 AM
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Fuse

Doc here,

Pull the dome light and fuse or disconnect the lamp socket..

Replace the Tail light / Instrument fuse and see if it stays lit without blowing the fuse..

If so you have an interaction between the lighting system and The courtesy lamp..and need to track that down..

The Dome runs off a switched ground..( Dome light post switches) The tails and Instruments run off a switched power..If the two were to be crossed up, through an unlit or dim dome filament to ground, (loaded Ground) the resistance would be almost nothing...and blow the fuse for the tails out...

If it can't be found in the wires, then look to the dome on switch, At the headlight switch, and the lights on function for an internal short...

Doc
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Old 09-22-2005, 01:08 PM
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I unplugged the headlight switch and put a new fuse in (last one) and I had brake lights. I then plugged it back in, everything fine. Then turned on park/head lights, fuse blows. Now tell me if I am wrong but is my head light switch bad. As I said before, the "Dimmer power" prong is loose (probably causing a short) on the switch and on the plug around this wire was also melted a little. I am going to try and dig up another fuse and pull the head light switch from my truck (I know it is good) and see what happens. Thanks again for the help.

hotrod48
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Old 09-22-2005, 01:50 PM
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If the plug is melted then it is/was probably a bad connection and it probably now internally shorted. This could be checked with a volt meter or an OHM meter. If you disconnect the battery you can still check for shorts and not keep burning through fuses. The other thing that sometimes can make troubleshooting electrical issues easier is to replace the fuse with a resetable circuit breaker. Make sure you replace both the switch and the connector if either is burnt.
Once you replace the obviously defective parts you can continue troubleshooting if still needed.
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Old 09-22-2005, 03:48 PM
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Thanks for the advice. How would I check it? How can I check for shorts with the battery disconnected? I will try to get a resettable circuit breaker. I don't know much about electrical stuff but I catch on quick and have a feeling I going to learn quite a bit here. Thanks again.

hotrod48
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Old 09-22-2005, 04:56 PM
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Quote:
Originally Posted by hotrod48
I unplugged the headlight switch and put a new fuse in (last one) and I had brake lights. I then plugged it back in, everything fine. Then turned on park/head lights, fuse blows. Now tell me if I am wrong but is my head light switch bad. As I said before, the "Dimmer power" prong is loose (probably causing a short) on the switch and on the plug around this wire was also melted a little. I am going to try and dig up another fuse and pull the head light switch from my truck (I know it is good) and see what happens. Thanks again for the help.

hotrod48
Doc here,

Quote:
Doc here,

Pull the dome light and fuse or disconnect the lamp socket..

Replace the Tail light / Instrument fuse and see if it stays lit without blowing the fuse..

If so you have an interaction between the lighting system and The courtesy lamp..and need to track that down..

The Dome runs off a switched ground..( Dome light post switches) The tails and Instruments run off a switched power..If the two were to be crossed up, through an unlit or dim dome filament to ground, (loaded Ground) the resistance would be almost nothing...and blow the fuse for the tails out...

If it can't be found in the wires, then look to the dome on switch, At the headlight switch, and the lights on function for an internal short...
Of course your not going to blow a fuse IF you unplug the Switch, you have just severed the power to the system...Like saying if I pull the battery cable, it stops blowing fuses...

Loose wires in connectors will cause intermittent's and need addressing AFTER you find the source of your short...provided they haven't melted through the connector and physically touching the next circuit...and then at that, everything at that switch is ON power...no ground runs through it...So at best you'd get another circuit lit or on when activated by another...The exception to the rule is if the wire was physically touching the switch body (ground)

Pull the Dome light socket..and lamp, replenish the tail fuse, and test it again...If it blows you most likely have a short at the switch rheostat / dome switch to ground,

To verify the wire to the dome light is good, with the dome socket still removed, measure with a DMM or ohm meter on an R x 1 Scale or Auto range at the switch the dome light wire coming out of the switch...

It should read infinite..If it reads 000, go to the LEFT door post switch and pull the wire (s) from the center terminal (should be only one terminal) measure again..should be infinite, If not you have a short ON that wire between that switch and the headlight switch...

If it is infinite, go to the terminal on the headlight switch and ground and set the switch for "Dome" if it shows 000, to ground you have a bad switch..If it shows infinite, pull the headlights "On", if it shows 000 when you go to on..to ground, you still have a bad switch...If it remains infinite your switch is fine..look farther into the dome/tail circuit..

Do this testing with the dome and tail light fuses removed or better disconnect the battery so you don't accidentally burn out your DMM hitting power on an Ohms scale...

Doc
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Old 09-23-2005, 10:46 AM
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Quote:
Originally Posted by hotrod48
Thanks for the advice. How would I check it? How can I check for shorts with the battery disconnected? I will try to get a resettable circuit breaker. I don't know much about electrical stuff but I catch on quick and have a feeling I going to learn quite a bit here. Thanks again.

hotrod48
If you have a diagram for the connector. You can check from any wire that carries power to any of the lights to ground with an ohm meter. If you find one with a dead short then you have a place to start looking. Note: that all may show some resistance unless you pull all the bulbs out.
I personally would replace the connector for the headlight switch and the switch before you go any further. It is aparent that they have both been hot and need to be replaced. The light switch could be shorted internally to the case. The plastic plug that is melted could also become conductive if it carbonizes.(sp)
I generally am not a parts replacer but when you an obviouly burn/damaged part, that is where you need to start
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Old 09-23-2005, 08:17 PM
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is your problem solved?
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Old 09-24-2005, 03:07 PM
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I did get it fixed. Thanks guys for all of the help. It turned out that the tag light wires had got pinched and were shorting out (It's a billet aluminum tag frame recessed in the trunk lid). Now that I got that fixed the car won't start. I probably unplugged something on accident and didn't know it, but this should be easier to find. Thanks again for the help and it helped me track down my problem.

hotrod48
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