The Ford Barn

Smofo · 02-16-2014, 10:10 AM

I have a 1928 Model A and had to replace unction box. The car has a 12v system and also has a petronix electronic ignition inside distributor. After replacing the harness to ignition switch and harness to starter and alt. I am getting a short from the yellow/black ammeter wire. I keep on referring to wiring diagram and all is correct(I hope). Also forgot to mention I replaced the ammeter too. The one in the car before the repairs was a little melted in rear of meter.

Can anyone offer any suggestions?

Tom Wesenberg · 02-16-2014, 11:44 AM

What ignition switch are you using and how is it wired to the system?

It's my understanding you can't use an original popout, which connects the ground side of the coil to the points.

P.S. · 02-16-2014, 11:47 AM

Quote:

Originally Posted by Tom Wesenberg

It's my understanding you can't use an original popout, which connects the round side of the coil to the points.

He means "ground" side of the coil.

MikeK · 02-16-2014, 12:55 PM

You said you replaced the junction box. Some of the reproduction boxes are known to have issues with the brass studs shorting through the back side of the box to the firewall.

Smofo · 02-16-2014, 01:44 PM

I thought of the screws in back shorting against the firewall and will definitely do that fix. However since I was trying to rule that out before, I wedged cardboard behind the screws to make sure hat was not the issue.
Can the wrong ammeter or bad one cause the short?

Its real funny, I reversed wire on ammeter and the problem is always the yellow/ black wire. As long as I leave that wire off the J box no short. Did I mention I installed new harness and looked at new wire to make sure its not chaffed again.

Smofo · 02-16-2014, 02:15 PM

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I also noticed that the yellow/black wire turns on lights and horn. so now I suspect a short in the lighting system

. I will replace the switch housing at the end of steering column and see if the short was starting from in there. Here comes some trial and error!!

Smofo · 02-16-2014, 02:17 PM

give me a pointer on where to start with meter. I have now narrowed it down to the lights and horn. Not very experienced with electrical.

AL in NY · 02-16-2014, 02:44 PM

Smofo, check the headlights first. Disconnect the headlights one at a time. Your problem may be on the headlight side of that connector.

Tom Wesenberg · 02-16-2014, 03:26 PM

Does the horn work OK? If not then start there by removing the rear cover, and see if the power lead is shorted. This is unlikely the problem because it shouldn't change by turning on the lights, and would likely be a full time short that would smoke the fuse or wires. I think the headlight sockets are the problem.

Smofo · 02-16-2014, 04:35 PM

Man if you can believe it, I traced it to the brake light switch. originally I disconnected one side of the switch and it was still shorting. Then I disconnected the other side of the switch and the short was gone. It was the brake light switch all along!!

Thanks for the tips.

By the way the after market junction boxes suck!! Need to upgrade another as posted in another thread.

02-16-2014, 10:10 AM	#1
Smofo Junior Member Join Date: Apr 2012 Posts: 6	12v electronic ignition-junction box problem I have a 1928 Model A and had to replace unction box. The car has a 12v system and also has a petronix electronic ignition inside distributor. After replacing the harness to ignition switch and harness to starter and alt. I am getting a short from the yellow/black ammeter wire. I keep on referring to wiring diagram and all is correct(I hope). Also forgot to mention I replaced the ammeter too. The one in the car before the repairs was a little melted in rear of meter. Can anyone offer any suggestions?

02-16-2014, 11:44 AM	#2
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: 12v electronic ignition-junction box problem What ignition switch are you using and how is it wired to the system? It's my understanding you can't use an original popout, which connects the ground side of the coil to the points. Last edited by Tom Wesenberg; 02-16-2014 at 12:17 PM. Reason: gee, i dropped my g

02-16-2014, 12:55 PM	#4
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: 12v electronic ignition-junction box problem You said you replaced the junction box. Some of the reproduction boxes are known to have issues with the brass studs shorting through the back side of the box to the firewall.

02-16-2014, 01:44 PM	#5
Smofo Junior Member Join Date: Apr 2012 Posts: 6	Re: 12v electronic ignition-junction box problem I thought of the screws in back shorting against the firewall and will definitely do that fix. However since I was trying to rule that out before, I wedged cardboard behind the screws to make sure hat was not the issue. Can the wrong ammeter or bad one cause the short? Its real funny, I reversed wire on ammeter and the problem is always the yellow/ black wire. As long as I leave that wire off the J box no short. Did I mention I installed new harness and looked at new wire to make sure its not chaffed again.

02-16-2014, 02:15 PM	#6
Smofo Junior Member Join Date: Apr 2012 Posts: 6	Re: 12v electronic ignition-junction box problem Sponsored Links (Register now to hide all advertisements) I also noticed that the yellow/black wire turns on lights and horn. so now I suspect a short in the lighting system . I will replace the switch housing at the end of steering column and see if the short was starting from in there. Here comes some trial and error!!

02-16-2014, 02:17 PM	#7
Smofo Junior Member Join Date: Apr 2012 Posts: 6	Re: 12v electronic ignition-junction box problem give me a pointer on where to start with meter. I have now narrowed it down to the lights and horn. Not very experienced with electrical.

02-16-2014, 02:44 PM	#8
AL in NY Senior Member Join Date: May 2010 Location: Southern Upstate New York Posts: 1,160	Re: 12v electronic ignition-junction box problem Smofo, check the headlights first. Disconnect the headlights one at a time. Your problem may be on the headlight side of that connector. __________________ AL in NY

02-16-2014, 03:26 PM	#9
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: 12v electronic ignition-junction box problem Does the horn work OK? If not then start there by removing the rear cover, and see if the power lead is shorted. This is unlikely the problem because it shouldn't change by turning on the lights, and would likely be a full time short that would smoke the fuse or wires. I think the headlight sockets are the problem.

02-16-2014, 04:35 PM	#10
Smofo Junior Member Join Date: Apr 2012 Posts: 6	Re: 12v electronic ignition-junction box problem Man if you can believe it, I traced it to the brake light switch. originally I disconnected one side of the switch and it was still shorting. Then I disconnected the other side of the switch and the short was gone. It was the brake light switch all along!! Thanks for the tips. By the way the after market junction boxes suck!! Need to upgrade another as posted in another thread.