Electrical issues?

[arefftx]

I can't get the lighting or horn switches to work even after replacing the lighting harness today. The starter works and the horn works when directly wired to the battery, there is a fuse next to the starter which I also replaced.n...any suggestions?

[Ordsgt]

There was an issue with some wiring harness that did not fit well into the switch not allowing proper contact. I also came across a switch (new) that was assembled wrong.

[arefftx]

The harness just came from Snyder's, how might I make sure the contact is being made ok?

[larrys40]

I install these all the time and I have yet to have one wired incorrectly.
Make sure the switch is turning. Do you know how to use a multimeter?
If so it’s easily to check out. With switch on low beam or high beam you should have a short between the yellow lead and the red or green respectively for low or high.
Check your voltages, make sure your fuse holder is good and proper voltage in both sides .
Model A wiring is pretty simple . The yellow lead at the horn is hot all the time, blue is your ground connection when the horn button is depressed.

I’d you have a meter use it and start looking at some of the points above.
I’m confident you will find the issue and learn something in the process.
Larry Shepard

[nkaminar]

As Larry said, use a multimeter to check voltages. Just trace the voltage from the post on the starter switch to where you find the fault. You can insert a needle into the wire to check voltage along the way. Use a pair of pliers to insert the needle. I found a fault that way at the holder for the fuse. I had to clean it up and use some electrical grease.

A good discussion on the wiring can be found here: https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

[rotorwrench]

Sponsored Links (Register now to hide all advertisements)

A multi-meter also has an Ohms meter setting where it puts a very small amount of current through a conductor to make sure it doesn't have an open circuit. This way a person can check through each wire or an entire circuit to see if it has continuity or not. A person can also check a circuit to ground to see it it has a short somewhere that it touching a part of the body or frame that it should not be.

Multi meters can check voltage and amperage as well hence the name "multi-meter".
They are not all that expensive in this day and age and are well worth the modest investment as a tool in electrical troubleshooting. A test light will work but the system circuit has to be powered up so a short to ground will just keep blowing fuses or burning wires in absence of fuse or circuit breaker protection.

[arefftx]

Ok Latest is the dash light works, fuse was blown on bypass but nothing on the light or horn work, think there might be a problem with the connection of the light switch it is extremely hard to attach the wire holder at the end of the switch.

[rotorwrench]

The two power wires for the horn and lighting are both connected to the generator (or alternator as applicable). The horn button grounds the circuit for its function.

The light switch spider and spring can be a bear to compress when trying to insert the little C-clip that retains the switch control rod. Most folks fabricate a tool to help apply pressure while still having enough room to get the clip in. The switch body & plate is held by the wire bale but it's generally fairly easy to pull into place. Everything has to be properly aligned before the switch body will seat all the way down onto the spider.

This is a good link for the model A electrical system. https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

[Y-Blockhead]

Originally Posted by arefftx

Ok Latest is the dash light works, fuse was blown on bypass but nothing on the light or horn work, think there might be a problem with the connection of the light switch it is extremely hard to attach the wire holder at the end of the switch.

Your problem may be that the light switch disk is too thick, as outlined in these instructions from Bratton's.

https://www.brattons.com/PDFs/20360%...%20FITMENT.pdf

[arefftx]

Thanks to those of you for the feedback & suggestions I'll try these ideas to see if I can isolate my problem. Thanks again!

[baba]

This is deja vu for me. I am still not out of the woods....

[arefftx]

My instrument panel light works, there is a spark on the distributor points so I am getting power there my problem is that I am immediately blowing the fuse near the starter even after I upped the fuse to 30amp...where might I locate the problem?

[flybob08]

Try the coil resistor - it may be shorting

[Bill G]

Originally Posted by arefftx

My instrument panel light works, there is a spark on the distributor points so I am getting power there my problem is that I am immediately blowing the fuse near the starter even after I upped the fuse to 30amp...where might I locate the problem?

Look to the connectors at the base of the headlight buckets. Those can be problematic if you have the original style connectors at the ends of the conduits. To isolate, unhook the connectors and turn on the light switch and see if it holds. That will tell you if it is at the headlight bucket connectors. The sockets on repop connectors tend to have wider than original pads on them on the female side of the connector. That would be my starting point.

It's been many years since I have been to Friday Harbor. Great place!

[arefftx]

I'm not sure what the be coil resistor in is?

[Bill G]

Originally Posted by arefftx

I'm not sure what the be coil resistor in is?

If you have a standard 6-volt system, your coil won't have an external resistor. You also said you were getting spark and the system blows fuses when you turn on the lights, so the lighting circuit is the culprit. The instrument light on the panel is a separate circuit than the headlights, so that's why it works when the headlights don't.

[nkaminar]

As Bill G said, disconnect the lights and see if the fuse blows. Or use the ohm setting on your multimeter and see if you have eliminated the short to ground. You could try disconnecting the horn too. If the short is not eliminated continue to use the ohm setting on the multimeter to find the short after disconnecting wires one at a time. You do not have a ballast (coil) resistor as they are rare on Model A's and if you have one and it is shorted to ground you should be able to find it with the ohm setting on your multimeter.

Read this: https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

[rotorwrench]

A 12-volt conversion may need a ballast if it has an original type 1.5 OHM primary coil. A 6-volt system with a 1.5 OHM primary coil needs no ballast to function correctly. Ford didn't start using a ballast till the V8 came out with the front mount distributor with integral coil. These coil designs required a ballast. When Ford went back to the can type coil in 1948 with the 8BA engine, the ballast was again deleted.

If it blows the fuse when the lights are turned on then the wiring to each lamp needs to be isolated and tested for a short to ground. As mentioned previously, the OHMs meter function is best for this type of test.