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Discussion Starter · #1 ·
Hi there, I have a 1961 impala.
The ignition harness that comes out of the fire wall on the driver side has an issue.

There is a line from the battery that goes into the ignition harness to the horn regulator. There is an in-line bus fuse before it reaches the regulator there’s another line from the horn regulator to the alternator.

When I turn the car on and then turn it off, the bus fuse, blows.

Previously, I fried that same line when I connected the battery, so I replaced it with a new power line with an in-line buss fuse that goes to this horn

I originally thought it was a short in my alternator, so I replaced the alternator but I still have the problem.
When this buss fuse blows, I can no longer turn the car on everything is dead.

I ordered a new ignition harness, but I have not put it on yet because I was scared that I would burn the wire in someway.

The harness is completely taped off on all the ends, so it cannot short, so the only thing connected is the alternator and the line from the battery.

Does anyone have any ideas of why this blows?
 

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Discussion Starter · #2 ·
The main power line is the red one that I replaced coming from the battery is the one that fried. The other line coming off the horn regulator goes to the alternator. I added the bus fuse because there was one there previously that burnt. I’m wondering if the horn regulator is the problem.

Motor vehicle Automotive tire Electrical wiring Tread Gas
 

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Try this, disconnect the alternator from the switch & temporarily connect something else that you know works fine to provide a load like your electric radiator fan if you have one or horn or something, if it still blows it can only be the switch. There only needs to be a short for a fraction of a second to blow the fuse, if the short was after the switch you'd expect the fuse to blow from a cold wire to a hot wire, but yours is happening hot to cold.
 

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Also, not sure about the U.S. but here there's no warranty on electrical parts they're non-returnable, although yours still essentially works so maybe you could demonstrate the fault to your supplier & try and have them replace it, certainly worth a try. But if they won't and you don't want to pay for another switch you could simply add a manually resettable circuit breaker into your power wire instead of the fuse you currently have, which would also conveniently serve as an anti-theft device. I wouldn't use an automatically resettable circuit breaker as it would also reset itself if you ever had an issue with something else going to ground when going from cold to hot.
 

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Discussion Starter · #9 ·
Try this, disconnect the alternator from the switch & temporarily connect something else that you know works fine to provide a load like your electric radiator fan if you have one or horn or something, if it still blows it can only be the switch. There only needs to be a short for a fraction of a second to blow the fuse, if the short was after the switch you'd expect the fuse to blow from a cold wire to a hot wire, but yours is happening hot to cold.
Hi there thank you for the detailed information. Are you saying my ignition switch could be blowing the fuse? If so, I have not yet replaced that I have only replaced my light switch. I miss spoke, so maybe my ignition switch has some sort of short?
 

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Sorry, long night & even longer day & I think i've probably got a short too, what i've said was based on- "so the only thing connected is the alternator and the line from the battery".
Somehow in my brain after I read that I was able to move your fuse from before the horn relay to before the ignition switch. As i'm sure you know the fuse protects the wiring to what is powered after it "the load" so a faulty ignition switch won't blow that particular fuse. I think the best thing is to have a look at this website & d/l all of it or just the electrical info & start using a multimeter to do some tests. I looked quickly & there are tests for the horn relay & just about everything else, have a good read & systematically go through it, there's even info on servicing the regulator internally.
 

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Discussion Starter · #11 ·
Sorry, long night & even longer day & I think i've probably got a short too, what i've said was based on- "so the only thing connected is the alternator and the line from the battery".
Somehow in my brain after I read that I was able to move your fuse from before the horn relay to before the ignition switch. As i'm sure you know the fuse protects the wiring to what is powered after it "the load" so a faulty ignition switch won't blow that particular fuse. I think the best thing is to have a look at this website & d/l all of it or just the electrical info & start using a multimeter to do some tests. I looked quickly & there are tests for the horn relay & just about everything else, have a good read & systematically go through it, there's even info on servicing the regulator internally.
Awesome thank you very much. I will look into it and check the horn relay. First the regulator is built into the alternator I was told.
 

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interesting that the light switch is powered through this same relay and you replaced it. The horn and lights work even when the car is off. to do this they have the same contact point hot off the battery. By the picture i think the horns are not currently connected. I would remove the light switch contact. Also the Generator light wire. I believe you have a wire touching ground somewhere and that makes the short blowing the fuse. Also think this way; the switch is off - fuse OK. Switch moves to accessory - fuse OK. Switch move to run - fuse OK. Switch move to start - fuse OK and back to run - fuse OK. Now back to accessory and fuse blows? Then off. keep talking and test the circuits that are activated. i had a horn wire pinched in my radiator and when the car stopped hard it was enough to cause a short in my alternator fuse. my fuse is 50 amp.
 
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