T-3 headlight date codes

[David L.]

I just found four T-3 headlights (2 high beam and 2 low beam WITHOUT the lines in the triangle) in my collection that I got from junk yard cars back in the 1980's. Unfortunately I cleaned two of them too much as I can only read the date codes on the two low beam headlights. The codes are as follows:
L
4001
22 4 28
12V

L
4001
72 2 16
12V

From what I found in searching through the archives they would be decoded as follows:
22 4 28 = February, 2nd line, 1964, 28th day of the month or February 28, 1964
72 2 16 = July, 2nd line, 1962, 16th day of the month or July 16, 1962

Is my decoding the dates correct?

Dave

[John F.]

Re: T-3 headlight date codes

David, Do you have an extra with the 3 prongs? I need one for a 62 without DOT markings.
John F

[Michael H.]

Re: T-3 headlight date codes

What I'd like to know is... is there a way to tell the difference between a 58-63 lamp and the new 64-68 lamp? (other than the date on the back side) Is there some ID on the front side? Or are they all exactly the same?

[David L.]

Re: T-3 headlight date codes

John,

My plan is to save four working T-3 headlights for my 1966 as I am currently using aftermarket headlights. I believe that I have more T-3 headlights somewhere in my collection. I will check to see what I have in the next few days. I remember testing some of my T-3 headlight back in the early 1990's and some of them had a very short life while others turned white. I even tested some NOS T-3 headlights with the same results. Old headlights are very sensitive. The best thing is to never turn them on.

Dave

[David L.]

Re: T-3 headlight date codes

Michael,

My 1963 Chevrolet Parts Catalog (Oct. 62) lists GM # 5948501 (single filament) and 5948502 (double filament) for 58-63 models in Gr. 2.726.
My 1964 Chevrolet Parts Catalog (Oct. 63) lists GM # 5956001 (single filament) and 5956002 (double filament) for 1964 models.

My July 16, 1962 T-3 4001 headlight looks identical to my Feb. 28, 1964 T-3 4001 headlight except for numbers and letters molded into the glass.
On the front of the July 16, 1962 headlight is a molded "1" over an "A" (10 o'clock position) and a molded "S 4" over a "A 3" (2 o'clock position). The back side has an anchor over the number "40".
The Feb. 28, 1964 headlight is as follows:
"1" over an "A" (10 o'clock position)
"S 5" over an "A 0" (2 o'clock position)
Anchor over "3A" on the back
These numbers and letters might just be mold numbers.

Basically the 1962 and 1964 T-3 headlights are the same as far I can tell.

Dave

On the

[Henry S.]

Re: T-3 headlight date codes

I just found four T-3 headlights (2 high beam and 2 low beam WITHOUT the lines in the triangle) in my collection that I got from junk yard cars back in the 1980's. Unfortunately I cleaned two of them too much as I can only read the date codes on the two low beam headlights. The codes are as follows:
L
4001
22 4 28
12V

L
4001
72 2 16
12V

From what I found in searching through the archives they would be decoded as follows:
22 4 28 = February, 2nd line, 1964, 28th day of the month or February 28, 1964
72 2 16 = July, 2nd line, 1962, 16th day of the month or July 16, 1962

Is my decoding the dates correct?

Dave

Dave,
I believe your decoding is correct.

Michael,
Have you checked Lectric Limited's chart? I don't know if it is exact or not but it appears to be close if not. According to LL the 58-59 bulb has the word "GUIDE" directly above the center T-3 in the triangle. The 60-67 T-3 has "GUIDE" at the bottom of the lens. The 58-67 triangle have no verticle lines within the triangle. The 68-71 T-3 has the "GUIDE" at the bottom of the lens also but has verticle lines within the triangle. I believe those are the only differences.

[Michael H.]

Re: T-3 headlight date codes

Michael,

Basically the 1962 and 1964 T-3 headlights are the same as far I can tell.

Dave

Ok, thanks David. I just wondered if there was a way to tell the difference between 58-63 and 64-68 from the front side. It doesn't sound like there is though. Sixty four was the year for the new brighter headlamps.

On used T3's, I've had lots of experience with used ones. You can test to make sure they work, then store them for the next ten years. During that time, what often occurs is a slight leak in the glass which allows the vacuum to deplete over time. When the lamp is tested again ten years later, the filament burns within just a few seconds.

[Henry S.]

Re: T-3 headlight date codes

Ok, thanks David. I just wondered if there was a way to tell the difference between 58-63 and 64-68 from the front side. It doesn't sound like there is though. Sixty four was the year for the new brighter headlamps.

On used T3's, I've had lots of experience with used ones. You can test to make sure they work, then store them for the next ten years. During that time, what often occurs is a slight leak in the glass which allows the vacuum to deplete over time. When the lamp is tested again ten years later, the filament burns within just a few seconds.

There was thread awhile back about using silicone sealer to keep them from leaking. Don't know if it will work but you're only out some time and a little caulk or epoxy. Seems like most all the T-3's work when you get them home from the junk yard even after sitting for decades, it's the shelf life that does them in.

[Robert K.]

Re: T-3 headlight date codes

I hadn't heard that they leak on the shelf. That is disappointing since 20+ years ago I collected over 50 T3s and have stored them ever since. I even had a few of the 56-57. Sounds like another box or 2 needs cleaning out.

[David L.]

Re: T-3 headlight date codes

David, Do you have an extra with the 3 prongs? I need one for a 62 without DOT markings.
John F

John,

I finally found my other T-3 headlights that have been in storage since May 1982. I sent you a PM.

Dave

[David L.]

Re: T-3 headlight date codes

Ok, thanks David. I just wondered if there was a way to tell the difference between 58-63 and 64-68 from the front side. It doesn't sound like there is though. Sixty four was the year for the new brighter headlamps.

Michael,

I just compared a 4001 T-3 bulb dated June 29, 1963, with a 4001 T-3 bulb dated May 16, 1964, and I see no difference other then some numbers and letters molded into the glass which probably designate with mold that the bulbs were made in. The difference must be internal.

Dave

[Michael H.]

Re: T-3 headlight date codes

Michael,

I just compared a 4001 T-3 bulb dated June 29, 1963, with a 4001 T-3 bulb dated May 16, 1964, and I see no difference other then some numbers and letters molded into the glass which probably designate with mold that the bulbs were made in. The difference must be internal.

Dave

The headlamp bulbs/lamps for 58-63 were different than the lamps for 64 and later. The difference was the candle power/brightness. For the new 64 model, almost all bulbs were a new design, which also required several new changes to the entire electrical system, including new design wiring harnesses.
I know of no physical difference in the appearance of the head lamps between 63 and 64.

[Chuck G.]

Re: T-3 headlight date codes

I "pirated" this picture/chart from someone, so I'd like to give that individual credit.

Hope this helps the discussion.

Chuck

[David L.]

Re: T-3 headlight date codes

Thanks Chuck,

This confirms what I have found about the date codes.

Dave

[Jim D.]

Re: T-3 headlight date codes

There was thread awhile back about using silicone sealer to keep them from leaking. Don't know if it will work but you're only out some time and a little caulk or epoxy. Seems like most all the T-3's work when you get them home from the junk yard even after sitting for decades, it's the shelf life that does them in.

My 65 still has its original lights so I sealed them with silicone. Can't say if it helps or not but it certainly can't hurt.