Testing T-3 Headlights

[Bob B.]

Hi all,

I am trying to decide which of a pile of T-3s that I will use for my car. I got to wondering whether there is some relationship between electrical resistance of the filaments and how long they may be expected to last after installation. Any ideas?

Thanks,

Bob

[Clem Z.]

do not use a full 12 volts to test them because

thay do not see a full 12 volts when installed in the car.

[Bob B.]

Re: do not use a full 12 volts to test them becaus

Clem,

I was thinking about using a meter to test the resistance. This is the standard meter that tests AC/DC, volts, amps, and ohms and uses four AA batteries. Any idea of the resistance (ohms) of good vs. bad bulbs?

Thanks,

Bob

[Dave K.]

Re: do not use a full 12 volts to test them becaus

I would think that a bad or burned out bulb would show an open circuit.

Dave K.

[John D.]

Re: Testing T-3 Headlights

Bob, I used to buy and sell a lot of T3's. Found out the best way to test them was with a 9 volt battery. Learned this from Bill Gilbert of our Pittsburgh Chapter. Bill just carried around a little 9 volt when walking the junk yards, etc. Never use a battery charger for sure as you will probably cook the bulb. They are delicate old bulbs. A while back on this board someone talked about putting a sealant around the contacts to help prevent leakage. Think it was Joe L that said that. Those low beams are hard to find. Recently put a NOS one in my 63 and was afraid to turn it on. My old one lite up real nice but the judges didn't like it cause it was black on top so I lost one point.

[Joe C.]

Re: do not use a full 12 volts to test them becaus

Bob,

If the seal for the electrodes has gone away, then the inside of the beam contains oxygen. This will immediately cause the filament to melt when it is energized.
If the beam tests OK, with no white smoke, and the glass does not look milky white, and without a black patina near the top, then it is worth buying. At this point I advise you to protect your investment by sealing the electrode interfaces with a good, high temp silicone sealant, like RTV red.
Good, working, SEALED original T3 low/high (#2) beams are becoming very hard to find. High beams (#1) are still relatively easy to find.

Joe