I keep burning out headlight bulbs...

[transalpian]

Greetings!

I keep burning out headlight bulbs.

I am running IPF E code conversion lamps on a SMS direct to battery harness (with relay). I run a GM 12si 78A alternator with an oversized (8 gauge) wire to the battery (to the starter solenoid actually).

I keep burning out headlight bulbs. I get maybe a month out a set of H4 bulbs. I've tried high wattage, low wattage, extended life, and the cheapo models. I get maybe a month out of any of them.

My gut tells me I am getting high voltage to the bulbs, but my battery reads 14V when the truck is NOT running.

Where should I be looking?

EDITED TO ADD:

My mistake, the battery reads 14V when not running. At idle (or at higher revs), the battery reads 17V. This feels like my problem?

AND when I move the sense wire coming off the alternator, the voltage when running drops to 14V.

Loose sense wire. Now to tighten it up so I don't keep blowing headlights bulbs, or worse...

[transalpian]

And one more question for the electrical genius-es (genii?) of the board:

What would happen if I put 24V rated bulbs in my circuit?

[o2batsea]

I would have the alternator tested. That voltage seems hiah and the VR may be bad in that alternator. Alternators are all or nothing. That means when they charge the charge with all they got. Your voltage and therefore wattage is prolly what's killing the bulbs and everything else.
If you put 24 volt bulbs in a 12v system they will burn half as bright.

[superstator]

Definitely sounds like you solved it - just from the headline I would have assumed some kind of regulator problem. Your battery should read 12.6v when not running, though. A higher reading would mean it was significantly over cooked by the high voltage, and may be damaged.

24v bulbs running on a 12v system would be quite dim.

[yorker]

At idle (or at higher revs), the battery reads 17V. This feels like my problem?

Yeah overdriving the bulbs causes an exponential decrease in their lifespan. Fix your alternator.

[SafeAirOne]

One thing to note--If your battery was getting overcharged as a result of the bad voltage regulation for a while (long enough to go through several headlamps?) the performance/lifespan of the battery likely has been negatively impacted.

[mearstrae]

A GM alternator should read 13.8 to 14.2 volts. So, as is said, an internal regulator problem. Have the battery checked out for overcharge damage.

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