"short" on patience

[sethkestenbaum]

Ah, smoking wires.... just what I wanted.

I went for a drive yesterday after having rewired parts of the car. Smoke appeared to be coming from two places. First, there was smoke from the wire that connects the junction box and starter. Second, there was smoke in the light switch housing (my poor new wiring harness has now officially been broken in).

1) I've just replaced the wire from the junction box to the starter and from the junction box to the cut out. I figured that they were fried. The wiring harness seems ok so I am leaving it alone. I do want to replace the switch housing which may be half repro and half original but has always given me problems. I am not replacing this today.

2) I opened up the junction box and cleaned/tighten all connections. I left the small wire to the starter from the junction box disconnected on the starter end. If I tap the wire to the connection on the starter there is no spark. It is my understanding that this is a way to check for a major short.

3) When I "test" the horn and headlights, the horns seems better than it was (which I figure is a function of the new wiring). With the engine off and the key off, I get -8 drain with the parking lights on and -20 drain (the ammeter pins itself) with the brights on. The ammeter pegging itself to -20 worries me. The ammeter is a repro. I have the 32/50 bulbs.

Any thoughts/insights? I don't want to test the wiring by driving. I do not have an inline fuse (but will be installing one soon).

[Brentwood Bob]

the replacement junction boxes can short to the firewall.

[sethkestenbaum]

Original junction box.... modified bullet connected headlights

[Brentwood Bob]

Read a recent post with brites and dims both lighting after installing a new harness. the bullet connections are questionable. I have replaced the new blunt ones with earlier ends.
I also thought you might look at the dash connections to see if there is contact with the gas tank. Bob

[sethkestenbaum]

I decided to check things "one by one". To do this I opened up both headlights from the front and removed all bulbs. With the car off and the battery connected, I figured that there would be a draw in amps ONLY if there was a short. The exception to this is that a draw will still occur from the rear light (when you have the brights or regular lights on the rear lights go on). At all settings, the ammeter did not peg. I am assuming NO SHORT. I then checked "bulb by bulb". The draw shown was larger than I expected but consistent. With headlights "on" but no bulbs = the draw was a rear light draw of 7 amps. With one bulb installed the draw was 18. With two bulbs the draw was 20 but if I hit the horn I could see the meter move more. With only the OTHER headlight bulb installed 18.

My thoughts now are that the repro ammeter is an exaggerator. This said, I am still hesitant to test the new wires. thoughts?

[Patrick L.]

Sponsored Links (Register now to hide all advertisements)

If you did not have the headlights on when you had the 'smoke', then I doubt the new bullet connectors are the problem. [Even though I don't like those connectors].
The problem could be in the switch itself.
Regarding the terminal box, it seems like there is power going to ground somewhere.

[ericr]

part of the problem with matching a lower repro light switch cover with an original upper cover, in my experience, has been that the little dimples on the repro lower cover really don't hold well into the upper cover. could your lower cover have slipped slightly and grounded out on the hot wire on the switch plate (the yellow wire)?

[sethkestenbaum]

Ericr, it is possible as well.

[Bob C]

You can get this from the English car parts houses.

Bob

[sethkestenbaum]

Bob C, that is funny. I'll take a full jug.

[Mike V. Florida]

Originally Posted by sethkestenbaum

Ah, smoking wires.... just what I wanted.

I went for a drive yesterday after having rewired parts of the car. Smoke appeared to be coming from two places. First, there was smoke from the wire that connects the junction box and starter. Second, there was smoke in the light switch housing (my poor new wiring harness has now officially been broken in).

1) I've just replaced the wire from the junction box to the starter and from the junction box to the cut out. I figured that they were fried. The wiring harness seems ok so I am leaving it alone. I do want to replace the switch housing which may be half repro and half original but has always given me problems. I am not replacing this today.

2) I opened up the junction box and cleaned/tighten all connections. I left the small wire to the starter from the junction box disconnected on the starter end. If I tap the wire to the connection on the starter there is no spark. It is my understanding that this is a way to check for a major short.

3) When I "test" the horn and headlights, the horns seems better than it was (which I figure is a function of the new wiring). With the engine off and the key off, I get -8 drain with the parking lights on and -20 drain (the ammeter pins itself) with the brights on. The ammeter pegging itself to -20 worries me. The ammeter is a repro. I have the 32/50 bulbs.

Any thoughts/insights? I don't want to test the wiring by driving. I do not have an inline fuse (but will be installing one soon).

Let's look at this a piece at a time;

" First, there was smoke from the wire that connects the junction box and starter."

That's the wire that a lot of owners install a fuse in line. Since the next place the wiring goes is the ammeter and you did not say the ammeter wire was burned, I'm going to guess like other that the terminal box screw is the problem and it shorted to the frame. A mod for the box is to replace the two screws with ones made from brass. File the head so a screwdriver just fits in the slot. Tighten the nut in the box then fill the recess where the head is located with epoxy.

You also mention "...and from the junction box to the cut out. I figured that they were fried." That one would only burn only if there were a short to ground at the cutout, (if the wire from the cutout to the light switch was still good.)

Now lets look at the lights," -8 drain with the parking lights on and -20 drain (the ammeter pins itself) with the brights on". is way too much for stock bulbs. Which filament is turning on for the parking and are both turning on for Brights?

[Tom Wesenberg]

"My thoughts now are that the repro ammeter is an exaggerator"

You could be right, as the taillight should NOT draw 7 amps.
Any chance the brake light is on at the same time?

[ronn]

"short" on patience

could always hit a hospital............................!

[MrTube]

Doesn't the "A" ammeter have a shunt resistor on the back of it?
Is the resistor there? Is it good?

An open or missing shunt resistor would peg the ammeter with almost no current draw.

[Tom Wesenberg]

The Model A doesn't have a shunt resistor. It's built so all the current through it flows through the curved brass bar inside the meter. This sets up the magnetic field to deflect the needle, which is otherwise held in the center position by the C shaped magnet.

[sethkestenbaum]

I took a few minutes today to try to see if I could find the short. With all hooked up but the starter to junction box connection (and with the ignition off), I tested for shorts again at each setting.... and got a spark between the starter and junction box when turning the headlights one click counter clockwise. I opened the light switch housing and started to fiddle and the brass ring fell right out. My attempt to fix it didn't work and just bent the ring. OK, I now NEED a new light switch. Berts reported that they were out. Who makes a "GOOD" replacement?

[Mitch//pa]

nobody..
find a good used assy

[ericr]

don't give up the ship....

PM being sent

[Quigley1930]

I just went through this. NO ONE has the switch. I finally found an original and all is well.

Sewall

[Tom Wesenberg]

I see original light switches quite often at swap meets, and at Model A national meets. Someone must have one for sale.