48 Ford Super Deluxe - Lighting Problem

[Cora1948]

This just started. The only lights that work are the headlights. No instrument panel lights, no parking lights, no tail lights and no break lights.

I traced the circuit chart and used the voltmeter and the only circuit on the “left side of the chart” working is the headlights (and high beams).

Both circuit breakers (above instruments under dash) are getting power (both posts of each breaker are getting 6v) and I’m getting power to both battery connections to the light switch. Assumed is was the switch - just replaced it and that’s not it.

What else? Am I missing another breaker? There is (I think) another breaker on the firewall near the power top switch (convertible) that doesn’t appear to be getting power, but power Top works - didn’t test while running the power top, so might be that that circuit is only hot while running.

[ravedodger]

Interesting. I’m having a similar problem, except all my lights work but my headlights. I put an ohm meter on my headlight switch and found I wasn’t getting power from the forward battery post to the headlights when the switch was in the headlight position.

[TJ]

Originally Posted by Cora1948

This just started. The only lights that work are the headlights. No instrument panel lights, no parking lights, no tail lights and no break lights.

I traced the circuit chart and used the voltmeter and the only circuit on the “left side of the chart” working is the headlights (and high beams).

Both circuit breakers (above instruments under dash) are getting power (both posts of each breaker are getting 6v) and I’m getting power to both battery connections to the light switch. Assumed is was the switch - just replaced it and that’s not it.

What else? Am I missing another breaker? There is (I think) another breaker on the firewall near the power top switch (convertible) that doesn’t appear to be getting power, but power Top works - didn’t test while running the power top, so might be that that circuit is only hot while running.

I saw your question on the V-8 club website also and left you an answer. I believe you have a grounding problem. I have found that post war Fords(I have owned 3) need to have good clean grounds to the tail lamps etc.

[rotorwrench]

It could be the way the light switch was connected or there could be an internal problem with the switch. Generally if there is a ground problem, it won't affect all of the minor light circuits at once. The circuit breaker actually has two breakers in one. The H terminal on the breaker is for the power to the headlamps. The A terminal on the breaker is for all the other lights. It there is a short in the running lights, brake lights, or other associated connections to that breaker terminal then the breaker will kick open. It should reset after the short is repaired. It could also be a faulty breaker and especially if it won't reset.

http://www.vanpeltsales.com/FH_web/F...1946-48car.jpg

[fordor41]

"IF" I remember correctly my '41 had 2 power connections on the h.l. sw. 1 for headlights and one for the rest. '48 may be the same.

[Cora1948]

Sponsored Links (Register now to hide all advertisements)

The light switch does have 2 power in terminals from the battery. Both are getting power in (true for the prior switch too). I might hot wire one of the terminals directly to see if it is the switch.

I will check the brake switch today to see if there is any power there. My guess is no.

I’m thinking its a circuit breaker. I see the two attached to the dash. With the light switch off, they are all hot. When the light switch is on headlights, the post of the CB nearest to the passenger side doesn’t get power. Could that be the issue?

[rotorwrench]

It sounds like a short in the system. It could be either wire to the tail light housings or it could be the wire to the front park lamps.

A person can disconnect one wire at a time to see if the short can be found. You can start at the breaker where the three wires connect on the A terminal. If that doesn't help then go on to the light switch. The wires really should be isolated from each other and tested with an Ohm meter for continuity and short to ground. A person can also go the other way around and check the long wires from the tail lights first then work it to the two switches.

What kind of shape are the wires in on this car?

[Cora1948]

Wires are in great shape - for 75 year old wires. Car has been in the family since new, all original, 67k miles, always garage stored.

I think I need some help understanding the breakers and the posts. There apart to be two breakers under the dash (mounted above the instruments on the back side) side by side. I can take a picture.

There is another breaker on the firewall by the power top pump.

I have a volt meter and circuit tester, so I could poke through some of the wires to check for current.

On the on switch, I could take the out wires off and attach them one at a time and narrow down the particular circuits.

[TJ]

Frankly I would not trust 75 year old wires.