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Picked up a pair of T3 headlamps and need to bench test before offering them up on the FS page. One has two prongs and the other 3 prongs, I'm assuming high beam and low beam. But how to bench test? I have a useable 12v battery.
Sorry, I have to call you out on this. A running car will throw 13.8 - 14.5 volts at those headlights without burning them out. A fully charged 12 volt battery is at 12.6 - 12.7 volts. If that burns out the bulb it was junk to begin with!
bench test with ground wire on the left terminal.
Left as you are sitting in the car. The 2 terminal bulbs are high beam only. The 3 terminal bulbs are high and low.
I would agree. One of the "common' upgrades is to use relays on the headlights to give them a full voltage rather than the sometimes significantly dropped voltage seen through the headlight switch. ( And less amp draw through the old switch as another bonus)
That said, if you're working on 50 year old T3 bulbs, chances are they are on the edge of burning out pretty quickly regardless of them getting 10 or 13.8 volts
M
The outside lamp is duel element, the inside lamp is a single element.
Using the wiring in your car just unplug both your lamps from either L or R sides and plug the lamps your testing in.
No need to mount them as they are grounded through the connector(s)
If not here is a diagram I made on how they are wired.
Testing them with a fully charged 12 volt battery power should not hurt them. A lower voltage may cause them to pull slightly more current and this might hurt the element more.
To be sure of the prongs you can simply pull one of them off the Corvette and measure them.
Like mentioned above one of the best things you can do to your C3 is to ensure that your headlights get full battery voltage when running. I have seen many Corvettes that have 10 volts getting to their headlights while running and this reduces the amount of light the bulb produces by a fairly large margin.
Bench Test T3 Headlamps
