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Old 06-27-2013, 06:27 PM   #1
Mercman53
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Default Electrical Problem

Hello Gents,
I've just rewired a 1931 Model A with original wiring harnesses, main lighting, dash and engine, purchased from Sacramento Vintage Ford. Everything went swell until I connected the Battery. Seems Ive got a short in the system. Ive narrowed it down to the Ammeter. But being a novice in the electrical area my question is: Can a bad ammeter cause a short as in when I try to connect the battery the saftey fuse blows immediately? I only get the sparks when the black and yellow wire is connected to the ammeter or gen cutout. If I disconnect it from either end then I get no spark when I connect the battery cable but then again nothing works either. I sure hope this makes sense and someone can help.

Thanks,
Mercman53.
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Old 06-27-2013, 06:58 PM   #2
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Default Re: Electrical Problem

Good luck, it will be interesting to read all the different cures. Bob
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Old 06-27-2013, 07:14 PM   #3
Mitch//pa
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Default Re: Electrical Problem

are you connecting your battery properly. the original system has positive ground so the plus goes to the frame and the negative to the cable that goes to the starter
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Old 06-27-2013, 07:27 PM   #4
Bob C
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Default Re: Electrical Problem

I would disconnect the wires going to the horn and light switch from the cut out and see
what happens.

Bob
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Old 06-27-2013, 07:29 PM   #5
zzlegend
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Default Re: Electrical Problem

Does this help. Just a thought.

http://www.fordgarage.com/pages/awiringdiagram.htm
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Old 06-27-2013, 07:44 PM   #6
Mitch//pa
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as bob said remove the yellow wire on the cut out, its very common for shorts in the headlight circuit especially at the pig tails to the headlight housings
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Old 06-27-2013, 07:58 PM   #7
Mike V. Florida
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Default Re: Electrical Problem

Here it is without the link,

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Old 06-27-2013, 08:18 PM   #8
Mercman53
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Default Re: Electrical Problem

Thank you for all your fast replies. Here are the answers to your suggestions:
1. Yes I connected the battery correctly with the starter cable going to the Negative post and the Positive post cable going to ground.

2. I did disconnect the horn and light wires from the cutout and left only the ammeter yellow wire and poof the fuse still blew.

3. the Diagram shared with me here is what I used as well. But thank you for posting it for me.

Anything else I can do? Or could it just be a bad ammeter?

Thanks again.
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Old 06-27-2013, 08:25 PM   #9
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Default Re: Electrical Problem

If you disconnect the yellow/ black from the cut out and it doesn't blow then
the points in the cut out are probably stuck closed.

Bob
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Old 06-27-2013, 10:00 PM   #10
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Default Re: Electrical Problem

is this an original ammeter or a repro? if its repro ive heard they are of "hit or miss" quality and could be shorting one of the ammeter studs to its case (thus frame of the car) and popping your fuse that way.

just an idea i haven't heard yet.

do you know your way around an ohm meter or test light? (ohm meter better)
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Old 06-27-2013, 10:13 PM   #11
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Default Re: Electrical Problem

Could be a short to ground in the light switch. We had this problem with an aftermarket switch
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Old 06-27-2013, 10:19 PM   #12
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Default Re: Electrical Problem

Instead of blowing fuses, just leave it out and make a quick jump with a short wire and see if you have sparks. Or you could connect a test light to the fuse contacts. When you find and fix the short, the test light will go out.

If the fuse doesn't blow when you remove the terminal box wire from the cutout, then the ammeter must be OK, and the problem is in the cutout. The insulator might be missing, or the screw might be too long and shorting inside the case.
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Old 06-27-2013, 11:53 PM   #13
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Default Re: Electrical Problem

As suggested in an earlier post.. if you have/can use a volt ohm meter to troubleshoot it is best. You have a short somewhere that is creating a load big enough to blow the fuse....If you're not good at the meter eliminate some items... dash light ( remove wire from generator and leave safely disconnected so as not to short.... check terminal connections at terminal box and instrument panel. While at the terminal box and with power applied till fuse blows see if the terminal studs are warm... if so they may be shorting out against the firewall if it's a repro box with screw studs. The originals are better. The repros come loose and must be tightened before installation, I then fill the back side with epoxy on the screws before installing so they can never short or back out. You may also have a short in the distributor or ignition cable but potentially they won't always blow a fuse so quick. if you know how to use a meter start unloading things and check for a short to ground.. as I said your main areas to look are instrument panel, terminal box. Also, make sure your connection at the starter switch is good. wiggle the battery cable.. .if it moves at all remove the top nut, both cable and wire, and tighten the lower nut first, then re-install bat cable and yellow wire and retighten (doing all this with battery disconnected of course).

I feel a real need for volt/ohm meter instructionals... Next spring at the MARC Membership national I'll be doing a seminar on "how to" use a meter and troubleshooting along with some hands on time for all.

Drop us a note and let us know what it is.
Thanks,
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Old 06-28-2013, 12:12 AM   #14
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Default Re: Electrical Problem

Are you using the insulated nuts on the amp meter wire posts?
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Old 06-28-2013, 02:28 AM   #15
Mike V. Florida
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Default Re: Electrical Problem

Unfortunately blowing the fuse when you hook up the wires to the ammeter tells you only that the wire from the battery is good and the problem could be any where else in the system.

If it were me I would take the advice already given and remove the wires from the cutout and see what happens. By removing the wires from the cut out you have removed the lighting and horn from the circuit. If you still have a problem it is in the ignition circuit. If you dont have a problem connect the wires that were on the cut out but don't connect them to the cut out and see what happens. If everything works then the problem is the cut out.

Use the drawing, remove branches from the circuit and keep at it. You will find it.
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Old 06-28-2013, 04:32 AM   #16
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Default Re: Electrical Problem

"2. I did disconnect the horn and light wires from the cutout and left only the ammeter yellow wire and poof the fuse still blew."

This is what tells me the problem is in the cutout, since you said in post #1 that when you disconnect the yellow/black wire from the cutout you don't have sparks. See my post #12. If you have a spare cutout, you could also just swap them, if it's a good cutout.

The cutout has a thin and thick insulator. The thin one goes on the generator side and the thick one on the output side. Be sure the screws going through each insulator aren't too long.
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Old 06-28-2013, 05:05 AM   #17
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Default Re: Electrical Problem

do not overlook the junction box for a short.
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