Warning about dash LED bulbs

[jclotz]

I searched on this topic and couldn't find anything, so apologize if already covered.

I recently replaced my dash bulb lights with Superbright LED's. Took it out for a drive and noticed no charging was happening - the red alternator light wasn't going out and my volt gage was only showing 12V, not the standard 13.5. Killed my battery.

Long story short, I replaced the alternator bulb back to standard and all good now. Guess because current from the blue wire from the alternator passes through the bulb, it's not happy with the LED.

Anyway, just an FYI.

[911T1969]

Yes, the alternator needs the resistance from your dash light bulb to activate your charging circuit. That's one bulb that I didn't change to LED. You could add a resistor to the circuit though and make it work. That was too much work for me. Haha.

[Irhmsd]

I put the LED bulbs in my dash quite some time ago. 1974 model. No problems.

[HarryD]

Originally Posted by 911T1969

Yes, the alternator needs the resistance from your dash light bulb to activate your charging circuit. That's one bulb that I didn't change to LED. You could add a resistor to the circuit though and make it work. That was too much work for me. Haha.

Exactly. This web site may be informative: Understanding Alternators : How-To Library : The MG Experience

[wildthing]

I got LEDs from another Pelican. No issues since 2013.

[somoney311]

Only a few months but my 89 is a daily driver and no issues here.

[sugarwood]

"No issues" is not the point of this thread. Are you saying your alternator light works? You tested it?
OP is saying you will not know your alternator light isn't working until you're on the phone with AAA.

[wildthing]

He said red alt light wasn't going out which I took to mean it was on, and battery was in use. No?