Where's the Short? Help Needed!

[smurph]

I'm out at sea when it comes to the electrics. Here's what happened:
1) Lost the only key to my ' 29 Standard Coupe;
2) Pulled repro pop out switch free from dash to look for key numbers;
3) Got a replacement key;
4) Replacement key works but is not smooth as the original-- have to jiggle it to make it turn;
5) Fuse blows, and keeps blowing when replaced; battery goes dead;
6) Process of elimination ( horn and lights OK) leads to pop out switch or ammeter;
7) Ammeter OK, nuts tight;
8) Discover terminal post on pop out is loose and tighten it up;
9) Fuse can now be replaced without blowing;
10) Battery will not charge when connected to starter;
11) Disconnect battery from starter and try to charge battery again;
12) Battery holds charge;
13) Car starts in normal way and is warmed up;
14) Go for a test drive and make it about 30 feet when car goes dead;
15) Fuse has blown again;
16) Leaving ignition switch on, replace fuse, blows again;
17) Turn ignition off and remove key, replace fuse and it does not blow;
18) Car starts but I'm not sure what 's going on so I return to garage.

So where is the short?
A) Inside the pop out switch itself as a result of the balky key or screw post tightening?
B) In the wiring behind the dash which seems to be original, is in pretty rough shape, and which has been pushed around some by removing the dash and pop out ?
C) At the distributor due to pulling the wires inside the armored cable ?
D) Other?

Thanks in advance for your thoughts/help.
Smurph

[Gary WA]

Wire under dizzy shorting out,Switch shorting to dash-battery positive ground-switch can short out inside armored cable.troubleshooting tips.

[Joe K]

One of the techniques for problem solving of ANY problem is to "look for what has changed."

It worked before - you've obviously done something in your pop-out improvements which is taking the system down.

The repop pop-outs are notorious for developing shorts. Suggest you eliminate the pop-out first and try bridging the circuit between.

Check out the wiring diagram at http://www.webjunk.com/modela/wp-con...amcolor2sm.jpg

You can bridge from the red wire and go directly to the metal contact in the distributor using a jumper wire bought at Harbor Freight (or RadioShack - but they're more expensive.)

Then try your battery charge test, engine start, road test again.

Let us know what you find.

Joe K

[H. L. Chauvin]

Hi Smurph,

I have no idea what you are working with electrically; however, if I would arrived at your location tomorrow to resolve your problem with the entirely unknown wiring system that you have, (new or old), I would totally ignore all guessing, & what coulda or shoulda happened with this or that, before or after any electrical or non-electrical events.

I would have an analog volt multi-meter and begin at the main "Source"; i.e., an unconnected charged battery whereby I would measure the volts between positive & negative battery posts.

Remember electricity is very simple --- it travels in insulated wires very similarly to water traveling in pipes .... when the electrical insulation is damaged, the electricity leaks ... just like when a pipe is cracked, or not connected properly, water leaks.

Next I would carefully connect only one (1) electrical thing or wiring harness at a time, in sequence, until I would find the real problem.

Just me ....... I just never have time to jump around & tinker ....... I try to do everything once, move forward & try to avoid retrograde movements ... & never want to be stranded on the highway or have an engine die on a well traveled highway.

When finished as such, you will have enough peace of mind to travel to Alaska from NY.

Hope this helps.

[Bob C]

The ignition switch is connected to the ground side of the system
so a short there would cause the engine to quit but wouldn't blow the fuse.

Bob

[Growley bear]

Sponsored Links (Register now to hide all advertisements)

What Joe said, starting with the very first sentence.

Chet

Originally Posted by Joe K

One of the techniques for problem solving of ANY problem is to "look for what has changed."

It worked before - you've obviously done something in your pop-out improvements which is taking the system down.

The repop pop-outs are notorious for developing shorts. Suggest you eliminate the pop-out first and try bridging the circuit between.

Check out the wiring diagram at http://www.webjunk.com/modela/wp-con...amcolor2sm.jpg

You can bridge from the red wire and go directly to the metal contact in the distributor using a jumper wire bought at Harbor Freight (or RadioShack - but they're more expensive.)

Then try your battery charge test, engine start, road test again.

Let us know what you find.

Joe K

[jmeckel]

Assuming the only area you touched was the dash area, then the only items there that can blow a fuse (if it is still wired like orgnial, with a replacement switch), is the dash light or the amp gauge. Or the wires going to them. Take a look at those items by taking the dash back off and make sure nothing is shorting out. If that is not the problem, start at the battery and work out, following the wiring diagram, and use a good meter.

[Gunmetal blue2]

You my have a bad wire that is inside the cable that goes from the switch to the distributor.

[smurph]

Thanks to all for your thoughtful replies. Now a follow-up question:

What is the probability that the short is in the pop out itself rather than in the map light , ammeter, wires to the former behind the dash, or in the wires inside the armored cable?

Thanks again in advance,
Smurph

[Tom Wesenberg]

A bad popout switch might ground the points side of the coil, but it shouldn't make the fuse blow. Check the hot wires for shorts, such as the ammeter, and instrument light wire or socket.

[Joe K]

Originally Posted by smurph

Thanks to all for your thoughtful replies. Now a follow-up question:

What is the probability that the short is in the pop out itself rather than in the map light , ammeter, wires to the former behind the dash, or in the wires inside the armored cable?

Thanks again in advance,
Smurph

Hard to say. We don't know what condition your wires are in - or how much diddling you did with the fabric covering as you moved everything around.

You can take the wiring diagram given earlier, and "de-land" each wire separately at both ends. Then put a volt-ohm meter (or continuity tester) connected to the frame/battery clamp on one side and see if it makes the tester light up or the meter move. You could start at the terminal block on the half dozen wires that land there.

And in the process you'll not only find the short - but also learn a lot about your Model A.

As I said earlier, I'd try taking out the repop pop-out and see if that solves your problem.

Joe K

[jmeckel]

If the switch is wired as it should be, between the coil and the points, it will not blow the fuse, same if the armored cable was bad. If it did, every time the points closed the fuse would blow.

[tbirdtbird]

if the insulation on the instrument panel wires is as bad as you say then it is time for a re-wire. cheaper than a fire

[rocket1]

it sounds like a problem with the armored cable,Brattons makes a ign. jumper that would confirm the problem,or if you have a junk cable you could make your own,part# 16360

[smurph]

Electric woes continue!

Since the last posts, I have replaced the wiring behind the dash ( and boy did it need replacement!) and repaired a worn wiper wire. Put in new fuse which has not blown since. Bought and installed a new battery.

After hooking up the new battery, the car started right up. AHA, problem solved! But NOT SO FAST! Next morning the new battery is dead. I recharged it and conducted voltage and leakage tests on both POS and NEG terminals. I'm getting 6 volts, but am showing NO DRAIN on either pole. Yet the battery is discharging somehow?

Any ideas what's going on? How can the battery go dead without showing a drain when tested ? I have a few amateur ideas such as : short behind the junction box; short behind dash panel against the gas tank; "pigtail" short at distributor; short in armored cable; car not wired properly; etc.

Is there a method of isolating each element of the electric system so it can be tested for shorts one by one?

[Bob C]

How are you testing for drain? You need a test light, buzzer, or ammeter in series
to check for drain.

Bob

[Patrick L.]

How are going about checking for the draw ? Does the ammeter show a discharge ?

To check for a draw just remove a battery terminal, either one will do. Stick either your test light or volt meter between the bare battery post and the removed cable end. If the light comes on or you have a voltage reading then you have a draw somewhere. Just keep disconnecting things until the draw stops, thats your problem.

[smurph]

Using a Multi Meter I did the following:
Meter on V (volts) tested battery voltage, get a reading of 6 volts;
Meter on A (amps) disconnected + side and ran probes from battery + terminal to disconnected + ground strap-- got no reading;
Meter on A (amps) disconnected - side and ran probes from battery - terminal to disconnected - cable-- got no reading.

That's why I'm so puzzled. How can the battery be discharging when I'm showing no discharge on the Multi Meter?

[Mitch//pa]

you might be using the meter wrong. do some reading and try creating your own draw by turning on the lights or such

http://www.batterystuff.com/kb/artic...itic-load.html

[smurph]

Thanks to all for your patience on this thread. Some progress has been made , but I'm still not at the finish line.

When we last left off, the ammeter was reading backwards no matter how it was wired . That problem is now solved . To make a long story short, I rewired the car according to Les Andrews and that solved the ammeter problem. (As an aside, there's a lot of confusion and contradictory advice out there with the various wiring diagrams available).

As to the short, the problem persists. With all wires connected, including the red wire from ignition switch to coil, the battery will discharge overnight. With the red wire detached from the ignition switch, the battery will not discharge. Putting a multimeter on the red wire shows a discharge of 4.5 amps when connected to the ignition switch or to ground. So what 's causing the draw on the red wire ?

Best guess is a short in the ignition switch itself or in the wire in the armored cable to the distributor. But I can't figure out the mechanism by which this is happening!

Advice still needed. Thanks in advance.
Smurph