LED dash lamps won't dim

Cougar Community
1

Hello.
'67 standard Cougar. I recently replaced all of the dash lamps with this LED kit. The dash lamps are no longer dimable. I also have a set of AutoMeter gauges on the same circuit and their back lights also no longer dim. I wrote a review about this at WCCC and they said the LED lamps should dim and suggested I write here to see if anyone can help. TIA.

Spud

2

LEDs use so little current that the rheostat (variable resistor) in the light switch becomes useless. What you need to do is increase current flow in the dash light circuit. Easiest way is to add one normal light globe, say to the radio, then the circuit should work.

Also be careful, don’t add a LED to the brake warning light. This electrical circuit is a two way circuit and will not work correctly. LEDs are a diode which allows current flow in one direction only.

3

The more current the lighting draws, the more likely the rheostat is to be useful. For the two cars I’ve switched to LED IP lights, I’ve used the highest output set I could find. The result has been enough light to need to dim them, and a functional rheostat so I could dim them. That’s 2 for 2. Your results may vary.

4

Thanks, yearby. I’ll have to review the schematics about the parking break lamp. The LED kit only mentioned not to use an LED for the charging system.

I’ll have to add a separate lamp instead of using the radio, since I replaced it with a AutoSound unit years ago so I could get FM.

5

Thanks, PonyCarMan. What rating of rheostat did you use and how/where did you mount it?

6

The only thing I did was replace the incandescent bulbs with the brightest kit of LEDs. The rheostat is just another word for the dimmer in the headlamp switch. Both the cars have their original 50+ year old headlamp switch/dimmer assemblies.

It was an easy change.

How well did your original lights dim? You may need to clean the dimmer winding and wiper. If those are making poor contact the problems will be much worse with LEDs than with incandescent bulbs.

7

Spud,
I think you are confusing the brake fail warning light (loss of brake fluid) with the parking brake still on warning light circuit.

The brake fail light I was referring to shows when there is brake fluid loss. It should come on when first turning the key on (which is a test to see if circuit is working correctly), then stay off once engine is running. The light only stays on if there is a brake fluid loss.