The Ford Barn

The Ford Barn (
-   Model A (1928-31) (
-   -   Is There An Electrician In The House? (

joeypoconos 09-04-2012 06:02 PM

Is There An Electrician In The House?

Some weeks back I posted a thread regarding my 1929 Sport Coupe titled ďWhere Did All My Lights GoĒ. In short, when I turned on my dims to leave a cruise night, about a mile down the road, my dims became very bright and burned out. Switched to my bright lights, a few seconds later same results. Ditto for my cowl lights. LED brake and tail lights remained working.
To date, Iíve performed voltage and continuity tests , all appears normal.
Fiddled with my repro headlights and sockets thinking thereís a short somewhere in the circuitry.
I bought new bulbs and turned on the lights without problem. Ran the car at a fast idle, no problem. Took her out for a 5 or so mile jaunt, no problem. Back in the garage, turned the car off, ran the light switch through the three positions, no lights. Started the car, bingo, lights. Revved the motor, lights got very bright, pop goes the light bulbs. LED brake and tail lights not affected.
I went through the continuity tests and voltage tests again, same results, all appears normal. This time around I removed the wiring harness from the bottom of the steering column and ran some tests with a probe light. The three dimples controlling the dim, bright and cowl lights showed a very low glow on the test light. The battery dimples lit up bright, the brake and tail lights had no affect on the test light.
I ran a jumper between the ďLIVEĒ dimples and the dim, high and cowl dimples. All lights lit up and looked normal.
Next I REMOVED THE FUSE from atop the starter and checked the three (dim/bright/cowl) dimples with same result Ė a very low glowing of the test light. I touched the test light to various parts of the car (head light buckets, starter housing, generator housing, coil housing, radiator shell etc.) the test light glowed very dim.
My knowledge of electricity is along the lines Ė If I stick my finger in a light socket, itís going to hurt like heck. Iím stumped as to why the test light is glowing when the circuit is no longer fused and really stumped as to exactly how to find the short or whatever else could be causing this problem. Any help would be greatly appreciated, thank you.

BRENT in 10-uh-C 09-04-2012 06:34 PM

Re: Is There An Electrician In The House?

Since I picked up where you said you touched the test light to the generator housing, I am going to assume it does have a generator and not an alternator but none the less, I am thinking you still have poor ground(s) creating your issues.

P.S. 09-04-2012 06:45 PM

Re: Is There An Electrician In The House?

Since you apparently have a generator (not an alternator), you have a poor connection between the generator and the battery. The generator isn't "seeing" the battery voltage and ramping up intermittently. From what I can tell, there isn't anything limiting the voltage from the generator without a load on it.

The LEDs will withstand a lot of abuse. Since LEDs are likely current limited internally, you wouldn;t blow them out until the genrator voltage went WAY up.

The way to test this is do exactly as you did before, but put a voltmeter right across the headlamp socket. You should see around 7-8 volts (on a 6 volt system) with the car running and engine revved. If you see more than that, there's a problem between generator and battery.

Bruce Adams 09-04-2012 07:10 PM

Re: Is There An Electrician In The House?

If your lights are picking up voltage with the fuse out, I sense a SHORT TO GROUND where the bulbs are working in reverse, picking up their limited voltage from a ground connection, yet getting more voltage through the wires when the system is complete, yet still having THAT GROUND to want to escape to.
SO, now you have this HANGING SHORT TO GROUND, giving the system and the bulbs maybe five volts, but still being a GROUND SOURCE that the 30 volt juice wants to flow to, all THIRTY VOLTS, THROUGH the bulb, kabam !
This Short to ground is what your generator sees as a MEGA DEMAND and rushes to meet it, putting thirty volts or so to the lights (and ground) causing them to act like an exploding star.
Get an ohm meter from Harbor Freight FOR FREE or maybe eight dollars with no coupon, attach one end to say a head bolt, and go probing the head lamp connections to see where your SHORT TO GROUND is.
(It will be a similar number as when you touch the two leads -Infinity or therabouts) (BIG NUMBER of ohms)
Its FUN!
But then I used to do this kind of stuff for computers ,communication systems, and such.

Bruce Adams 09-04-2012 07:15 PM

Re: Is There An Electrician In The House?

CHECK where the negative lead goes to the starter for a short to ground where it passes through the firewall first.
Then go hunting from the headlamps to where a hot wire independent of the fused wire can short to ground intermittently.

BILL WILLIAMSON 09-04-2012 07:58 PM

Re: Is There An Electrician In The House?

Does your horn work? Twice, while dusting my car, bumped the horn wire conduit, hot wire came off inside horn cover, jiggled around at times causing an intermittant short. Bill W.

Bob C 09-04-2012 08:03 PM

Re: Is There An Electrician In The House?

Just a couple of questions that may or may not have any bearing on your problem. Does your test light
have a 6 or 12 volt bulb and where are you getting the power for your test light ( battery, starter, coil)
If your lights are getting bright and blowing out I also think you have a ground issue.
You are getting a dim test light when you test the dimples because you have the test light and the
bulb in the head light wired in series.


Tom Wesenberg 09-04-2012 08:58 PM

Re: Is There An Electrician In The House?

To check for a poor ground just connect the volt meter to the generator case and a good ground such as a head nut or starter case. Put the meter on the lowest volts DC and you should have NO reading. If you show any voltage, then you have a poor connection at that point (generator mounting bolt connection). Do the same by connecting the volt meter to the battery ground post and a good ground, such as the starter case. Again, NO voltage should be showing. Test the ammeter and terminal box posts by connection the volt meter to the two terminal box wing nuts. Again no, or almost no voltage should show. If you show more than about .1 volts, then you have a poor connection at the ammeter or terminal box posts. These are 3 easy to check likely spots for a poor connection. Since it cranks over just fine, I'd guess the battery posts and ground strap are OK, but that would still leave the generator mounting bolt connection, and the terminal box/ammeter connection, and the wires between the generator and starter switch.

For those wondering how the lights got power with a blown fuse, the generator is supplying the voltage as long as the engine is running. Remember, the lights pick up the power right at the cutout.

Popeye31 09-04-2012 11:51 PM

Re: Is There An Electrician In The House?

I have a quicker way to do this it will require two people. disconnect the positive wire on the battery. have your helper attach the aligator clip of your test light to the disconected pos wire. touch the point of your test light to the posative post on the battery. now if you have a short the light should be lit. now have your helper stay there wile you go to the driver side of the car open the hood and there are a few butt connectors on the wire harness right by the radiator for your lights and horn. disconnect them one at a time when the light goes out on the test light you have found the wire or cuircut with the short. as you disconnect them if the light dosen't go out plug them back in. if light doesn't go out for the lights,or horn go to the next component the genorator . disconnect the wire from the cutout switch. if light dosen't go out move to the distribution box on the fire wall. you should be able to find the short quickly using this method.

Tom Wesenberg 09-05-2012 01:19 AM

Re: Is There An Electrician In The House?

Popeye31, All true what you just posted for SHORTS, but the high voltage output that burns out light bulbs is cause by an unregulated generator having an OPEN. Generators with an EVR won't put out high voltage and burn out bulbs, even if the battery is taken out of the circuit. I do this often to show guys one of the benefits of an electronic voltage regulator.

joeypoconos 09-05-2012 08:03 AM

Re: Is There An Electrician In The House?

Bob C - test light uses AA battery. The test light is rated for use at 6 or 12 volts.

Tom W and Popeye - Good advice, I'm waiting for my helper to show up. Will run the tests you suggested.

Tom W - With the fuse removed and car off I still don't understand how I'm getting current (dim test light) to the dimples and the other areas I probed (i.e. buckets, starter body, generator body, etc). Is it possible current is getting past the fuse holder even though the fuse is removed?

Tom W- Mitch//pa also recommended an EVR, I plan to install one after I resolve this issue. At this point, I'm concerned an EVR will just mask a serious underlying problem that could result in a fire or some other not so nice condition.

Many thanks to all, I appreciate the feedback and will post an update, hopefully, in the near future.

joeypoconos 09-05-2012 08:47 AM

Re: Is There An Electrician In The House?

Popeye31 - performed first of the tests (positive cable to positive post). Test light DID NOT come on. Does this eliminate a short anywhere in the system and point to an un-regulated generator ??

Richard Wilson 09-05-2012 08:59 AM

Re: Is There An Electrician In The House?

I worked on a friend's Model A that had current across the safety fuse holder even with the fuse removed. The fuse posts were shorted out and I was able to fix.

Tom Wesenberg 09-05-2012 09:04 AM

Re: Is There An Electrician In The House?


Originally Posted by joeypoconos (Post 493153)
Popeye31 - performed first of the tests (positive cable to positive post). Test light DID NOT come on. Does this eliminate a short anywhere in the system and point to an un-regulated generator ??

:confused: The test light is used to check for battery voltage. If you probe the + battery post and + cable end on that post you are just checking for voltage drop. For this you need a DC volt meter with a low voltage reading. You also need current flow to measure voltage drop, so you crank the engine over while doing this test. You shouldn't be able to measure any voltage. If you measure voltage, the the clamp must be loose or dirty.

A test light is handy to locate where the voltage is or isn't. On the Model A the horn and coil should always have 6 volts and operate when a ground is sent by the horn button and by the points. The lights have power up to the point of the switches, so the headlights have power to the light switch on the bottom of the steering column and the brake light has power up to the brake light switch.

Bob C 09-05-2012 11:16 AM

Re: Is There An Electrician In The House?

Never had a test light with a battery, is it just a continuity tester or will it light up if you hook
one side to POS and other to NEG?

Marco Tahtaras 09-05-2012 12:26 PM

Re: Is There An Electrician In The House?

If I have this straight you are using a battery powered test light to check for continuity. If you have the clip hooked to ground and probe the switch contacts on the harness then the test light should come on showing continuity to ground as long as you have good light bulbs in place. The light will dim some as the bulbs act as a resister.

Whenever I've encountered the problem you describe in someone's car it has been a loose connection at either the terminal box or ammeter post. I've also heard via the forums that some fuse blocks fail due to loose rivets which would cause enough resistance to cause similar results.

joeypoconos 09-05-2012 02:19 PM

Re: Is There An Electrician In The House?

Bob C Ė The test light is just a simple device that has a bulb, AA battery and an alligator clip at the end of a wire and a pointy metal probe. The alligator clip goes to a good ground and the probe is placed on a connector (i.e. generator terminal). If electricity is present, the bulb lights up, no electric no lit bulb.

Marco Ė Iíve used the test light to probe every connection in the system. At all points the bulb lights. Iíve also used a multi-meter to check continuity throughout all circuits, all is in order. I checked amperage via the amp meter. With lights off and car off meter shows 0. With cowl lights on and car off meter shows slight discharge. With dims or brights on and car off meter shows -10 amps discharge. With car at normal idle and nothing on meter shows 0 amps. Car at idle and cowl lights on meter shows slight discharge. Car at idle and dim or brights on meter shows -6 discharge. Car at high idle or when revving engine with dims or brights on meter goes to +7-8 amp charge. With this latest iteration, the bulbs did not blow out.
Okay, now itís on to the voltage test using my multi-meter. Previously, my voltage tests showed 10 volts at the headlights with car at idle or high idle. I adjusted the generator third brush to +4 amps at high idle in hopes this would bring the generator voltage down. Today I re-tested the voltage throughout the system with the car running at high idle. Iím getting a consistent 10 volt reading everywhere.
Do these tests indicate that the system is free of a short(s) and that Iím dealing with a generator thatís not quite right? If so, will an EVR remedy this situation or should I have the generator checked/rebuilt then install an EVR.
My apologies for the long winded posts, just a novice trying to get to the bottom of all this before I decide to convert this thing to the largest, and only, 1929 Model A Sport Coupe pedal car.

Keith True 09-05-2012 03:06 PM

Re: Is There An Electrician In The House?

I've been reading all this,and come to the same answer.You have a bad connection.The battery is the regulator,and if the generator can't read it,it will make up to 40 volts.You should NOT be putting out 10 volts.The third brush regulates amps,not volts.Next,you are using a continuity tester,not a test light.A test light doesn't have a battery,a continuity tester does.When you stated you were getting power to things with the fuse out,I knew you were feeding the system yourself.I'm not buying that you have a short,a short won't partially feed a system,it will go bang,and melt something until it burns up and becomes an open.You need to start at the battery,connections,clean,bright and tight.Both inside and out.Cables rot inside the terminals too.Ground to frame,and from there to the transmission.Too much rust,paint and grease to depend on grounding through the mechanical parts.They're pretty simple,you just need the right tools and a little pointing in the right direction.

BILL WILLIAMSON 09-05-2012 04:05 PM

Re: Is There An Electrician In The House?

Make SURE every connection from cut out to battery is TIGHT & CLEAN.
Start at battery terminal at cut out, follow that wire on to junction box, on to ammeter, out of other side of ammeter on to the other side of junction box, and on to battery cable on starter switch. Check the nuts that secure the ammeter posts to the ammeter case for tightness. Remove wires, at junction box, one side at a time & tighten both sets of nuts in both sides of junction box. You will OVERCOME! Bill W.

Marco Tahtaras 09-05-2012 04:43 PM

Re: Is There An Electrician In The House?

There is a common misconception that a "bad or loose connection" means total failure. That is NOT necessarily the case. It can lead it intermittent failure (temporary loss of continuity) during vibrations, etc. Additionally, a bad or loose connection can have perfect continuity but cause resistance and not be able to deliver the required load. The best way I can describe it is like having your garden hose wide open and delivering 10 gallons per minute. If someone steps on the hose and partially flattens it the delivery is dramatically reduced.

It's worth mentioning that excessive resistance also creates heat at and near the point of the cause. While I've never tried it, I suspect if you drove the car for awhile (daytime, lights off) with the generator showing a charge, you would probably have a warm ammeter or wires at the terminal box.

I'll be VERY surprised if it isn't one of the three places I suggested.

All times are GMT -5. The time now is 11:41 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.