Dash switches - indication light

[jaykay]

How frequent is it that the indicator light or LED fails in our dash switches?

How would one test the indication lamp or LED without cooking the LED, anyway, in the process....

I am troubling shooting and conforming a bad switch would save a heap work back tracking on wiring.

I am working with a defrost switch...

[particlewave]

Test the LED with a multimeter set to diode check.

FYI: the LED working or not does not affect the function of the switch. It's also highly unlikely that the switch itself has failed. The contacts are quite beefy.

[jaykay]

Thanks man....I should look at my multimeter more carefully

... so just sequence through the terminals until a valid test set up signal is presented on a pair and then look for the led to light...

[particlewave]

If I remember correctly, the outermost terminals are the LEDs on the defrost switches, but it's really best to pop the switch apart and test them directly.
The notched side of the LED is negative.




Diode check is usually marked on the meter with a diode symbol, like this:



The diode check will illuminate the diode, though dimly. Again, best to remove the switch top to best ter see/test. It pops right off with little rocker tabs on each side.

[jaykay]

Thank you this is great information. I will have to get hold of just such a multimeter when I can. I was able to put 9 V to the switch and get the LED to function.....using a battery

I had to go brute force not having the proper tools. Hopefully I have not damaged the LED

Originally Posted by particlewave

If I remember correctly, the outermost terminals are the LEDs on the defrost switches, but it's really best to pop the switch apart and test them directly.
The notched side of the LED is negative.




Diode check is usually marked on the meter with a diode symbol, like this:



The diode check will illuminate the diode, though dimly. Again, best to remove the switch top to best ter see/test. It pops right off with little rocker tabs on each side.

[particlewave]

I'm sorry. I should have mention that the switch is wired for 12 volts (the LEDs have resistors wired in series). Your 9 volt method will/did work fine and won't damage the LEDs.

[jaykay]

No worries I believe I have found the problem. Yeah it's counter intuitive to have momentary contact switches on the dash with 12V umpf. If they had fixed throw capability(I hope I have the right treminology) you could wire light loads directly.