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byronpete21 06-16-2017 11:22 AM
Is this normal
 
Finally took the car out for a night drive. Noticed that my dimmer switch for the dash lights got quite hot after a few minutes. I know that rheostats heat up a bit, but is it normal for it to be painfully hot to the touch?

Thanks,
Byron

patrickt 06-16-2017 11:53 AM
Quote:
Originally Posted by byronpete21 (Post 1423997)
Finally took the car out for a night drive. Noticed that my dimmer switch for the dash lights got quite hot after a few minutes. I know that rheostats heat up a bit, but is it normal for it to be painfully hot to the touch?

Thanks,
Byron
No, it's not normal for it to be "painfully hot." You might want to take a quick voltage reading on your system and make sure you're within specs (around 14v, engine running above 2000rpm) and not somewhere too high. If the voltage is normal, then you can either replace the rheostat or add an in-line high-wattage resistor to lower the resistance you dial in on the knob, and thus lower the heat.

keezling 06-16-2017 12:58 PM
Had same problem found light switch had rivited buss bar connections with high resistance at the rivits. Flooded the connections with solder using a high wattage soldering iron and heating issue was gone. It would trip the internal circuit breaker for the headlamps shutting them off! Some warmth in switch is normal, not what you describe. Took me a while to figure that one out. Pushing 60k with no repeats.

strictlypersonl 06-16-2017 04:41 PM
My usual recommendation when dealing with the dash-light dimmer switch is to connect both the wires to the same terminal side. (Most of the switches we've got have two tabs on each side.) You'll get full brightness (usually not a problem) all the time. For the last 10 years we've had to scrape up NOS switches, and their quality leaves a lot to be desired. Unfortunately, the original Lucas switches haven't been made in well over a decade, and when we can find them at all, their price is ridiculous. To add insult to injury, I test them all and reject about 1/4 of them out of the box.

patrickt 06-16-2017 05:19 PM
Quote:
Originally Posted by strictlypersonl (Post 1424020)
For the last 10 years we've had to scrape up NOS switches, and their quality leaves a lot to be desired. Unfortunately, the original Lucas switches haven't been made in well over a decade...
That's the benefit of having a >10 year old ERA.:cool:

byronpete21 06-16-2017 06:57 PM
Thanks for the advice, I will take out my trusty voltmeter and start tackling the problem.

Byron

Gaz64 06-16-2017 11:28 PM
Also consider the total wattage of your gauge illumination bulbs.

The rheostat might not be up to the task.

It shouldn't get hot whether you are using the dimmer or not.

Are you using the dimmer?

Blas 06-19-2017 02:28 PM
Look to see if you have a clean tight grounds. A bad ground can cause high resistance which causes heat.

G-Pete 06-27-2017 09:58 AM
Lukas?

CHANMADD 06-27-2017 11:41 AM
I tried a few dimmers before I found one that was substantial enough.

strictlypersonl 06-27-2017 03:36 PM
Quote:
Originally Posted by Gaz64 (Post 1424043)
Also consider the total wattage of your gauge illumination bulbs.

The rheostat might not be up to the task.

It shouldn't get hot whether you are using the dimmer or not.

Are you using the dimmer?
Actually, the dimmer works by running the current through resistance wiring. By "definition" there will be heat generated, possibly the equivalent sum of all the lights in the circuit.

Gaz64 06-27-2017 04:50 PM
Quote:
Originally Posted by strictlypersonl (Post 1424676)
Actually, the dimmer works by running the current through resistance wiring. By "definition" there will be heat generated, possibly the equivalent sum of all the lights in the circuit.
I know how a dimmer rheostat works.

The owner has not stated whether he is using the dimmer resistance, and more importantly what total wattage is in the instrument lighting.

Dwight 06-27-2017 06:27 PM
headlight switch
 
I always use two relays for my head lights.
One for low beam & one for high beam controlled by the light switch. This take the amp load off the switch. The amount of amps to turn the relay on is very small compared to the amount needed for the headlight.

Dwight

byronpete21 06-27-2017 08:01 PM
Thanks again for all the good advice. Have been out of the country for a few weeks so out of contact with the internet and my car for awhile. Hopefully will get to it this weekend and have some more info to share.

Best Regards,
Byron


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