12 v dash light bulb part number needed

Mike_B · Post by **Mike_B** » Wed Oct 20, 2021 4:04 pm

Can someone tell me what the part number is for the dash lights when converting to 12v in my '53 M38A1. I tried #89 and they are to tall and hit the red glass lens...

Thanks,

Mike B

RonD2 · Post by **RonD2** » Wed Oct 20, 2021 5:06 pm

Hi Mike,
Without taking mine apart, memory tells me it's a #67.

Edit: I just looked online and it seems both 89 and 67 are the same height, so maybe not. I can pop my gauge plate tomorrow and take a look. Might be in my notes...

Mike_B · Post by **Mike_B** » Wed Oct 20, 2021 10:32 pm

Ron,

The one original #1251 24v bulb I have is 1.3" tall and the 12v #67 and #89 are 1.44" tall making them hit the glass.

I think I might have stumbled onto a bulb that will work, it's a "THHC 00059", 12v, 7 watt (the 1251 is 6.4 watt) and it's 1.3" tall.

https://www.lightbulbs.com/product/thhc-lighting-00059

Mike B

Post by **wesk** » Thu Oct 21, 2021 12:02 am

It helps to know which light sockets your cluster has. The M38 and the early M38A1 used the same lamp # 1251 and it was 1 7/16" tall. It was 3 candle power. The 12V 67 was 1 7/16" tall and 4 candle power.

#1251 Miniature Bulb Ba15S Base - 28 Volt 0.23 Amp 6.44 Watt G6 Single Contact Bayonet (Ba15S) Base, 3.0 MSCP, 2C-6 Series Filament Design. 2,000 Average Rated Hours, 1.44" (36.58mm) Maximum Overall Length (M.O.L.), 0.75" (19.05mm) Maximum Outer Diameter (M.O.D.), 0.75" (19.05mm) Light Center Length (L.C.L.).

#67 Miniature Bulb Ba15S Base - 13.5 Volt .59 Amp 7.965 Watt G-6 Single Contact (SC) Bayonet (BA15S) Base, C-2R Filament Design, 4.0 MSCP. 1.44" (36.58mm) Maximum Overall Length (M.O.L.), 0.75" (19.05mm) Maximum Outer Diameter (M.O.D.), 0.75" (19.05mm) Light Center Length (L.C.L.). 5,000 Average Rated Hours.

The late M38A1 (60's) and M170 used the M151 style instrument cluster which used an 24V 1829 which was 1 3/16" tall and 1 candle power.

Technical Data | NSN 6240-00-266-9940
Characteristic Specifications
BASE STYLE A18A MINIATURE BAYONET
BULB STYLE B25 T
BULB DESIGNATOR T-3 1/4
OVERALL LENGTH 1.188 INCHES MAXIMUM
BULB LIGHT TRANSMISSION CHARACTERISTIC TRANSPARENT
EMITTED LIGHT CHARACTERISTIC COLORLESS
FILAMENT DESIGNATION C-2F
WATTAGE RATING 1.960 WATTS
VOLTAGE RATING 28.000 VOLTS NOMINAL
CURRENT RATING FOR WHICH DESIGNED 0.070 AMPERES NOMINAL
LIGHT OUTPUT RATING 1.000 SPHERICAL CANDLEPOWER NOMINAL SINGLE RATING
RATED AVERAGE LIFE HOURS
AVERAGE LIFE RATING IN HOURS 1000.0
BURNING POSITION ANY ACCEPTABLE
FILAMENT HEAVY DUTY SERVICE RATING NOT RATED
LIGHT CENTER LENGTH 0.625 INCHES NOMINAL
III END ITEM IDENTIFICATION COMMUNICATIONS TERMINAL, SATELLITE AN/GSC-39(V)1; AIRCRAFT, (AC-130H
MANUFACTURERS CODE 96906
DEFINITIVE GOVERNMENT SPEC/STD REFERENCE MS25231-1829
MANUFACTURERS CODE 81348
NON-DEFINITIVE GOVERNMENT SPEC/STD REFERENCE W-L-00111/57

The # 89 lamp specs:

#89 Miniature Bulb Ba15S Base - 13.0 Volt .58 Amp 7.54 Watt G6 Single Contact Bayonet (Ba15S) Base, 6.0 MSCP C-6 Filament Design. 750 Average Rated Hours. 1.44" (36.58mm) Maximum Overall Length (M.O.L.), 0.75" (19.05mm) Maximum Outer Diameter (M.O.D.), 0.75" (19.05mm) Light Center Length (L.C.L.).

Another helpful Pub is Spence's handbook on Military Parts:

Trip · Post by **Trip** » Thu Oct 21, 2021 6:17 am

Wes,

Your depth of knowledge and your ability to answer (so quickly) and guide us newbies never ceases to amaze me.

Thank you and the others for all you do.

Trip

Post by **wesk** » Thu Oct 21, 2021 9:22 am

You are welcome Trip.

It has been the goal of this site since it's beginnings in the mid 90's to provide all the data we can possibly obtain for free to our members to help them with their projects.

It has always been a personal goal for me to encourage the use of all this free data and to try to always introduce the true story before all the guessing replies start.

aslanperro · Post by **aslanperro** » Thu Oct 21, 2021 9:26 am

Agreed how vast of info and data Wes can pull up on different topics.

I was looking for dash bulbs (all were missing) for mine few months ago and I measured the socket (the late style) as best as I can. Research on Internet of various base and bulb type to find out BA9S base and T3-1/4 to fit. Glad to know it matches with specs above. I ended up to get some LED equivalent on amazon.

Mike, I came across this vendor but I haven't used them. They have all kind of bulb types. #1251 is $0.47 each. #89 $0.39 I believe shipping is only 5.99
https://www.bulbtown.com/1251_Miniature ... ec1251.htm
https://www.bulbtown.com/89_Miniature_B ... _p/b89.htm

For those looking for 1829, pack of 10 for $3 https://www.bulbtown.com/1829_Miniature ... 1829bt.htm

Mike_B · Post by **Mike_B** » Thu Oct 21, 2021 9:02 pm

Wes, I have the early lamp holders that look just like my M38's.

The 1251 24v bulb I took out of the Hi-Beam socket measures 1.3" tall (1-5/16") and the chart you provided lists it at 1.44" (1-7/16') as does BulbTown.com. Did they change the spec on this lamp or is my lamp a weird anomaly at 1.3"?

I've tried both the #67 and #89 which are to tall at 1.44" (they hit the glass and don't fit). Anyone have a 1251 laying around they can measure? It might confirm if the literature is right or wrong...

I had no idea this topic was taking me off the deep end...lol! I figured this was an easy question as lots of M-Jeeps have been converted to 12v...

Mike B

Post by **wesk** » Thu Oct 21, 2021 9:38 pm

And the three 1251 lamps in your M38 measure ?

aslanperro · Post by **aslanperro** » Fri Oct 22, 2021 8:13 am

any photo of bulbs took out? what are their diameter?

RonD2 · Post by **RonD2** » Fri Oct 22, 2021 11:03 am

Hey Mike,
http://willysmjeeps.com/v2/modules.php? ... ht&start=0

At the risk of "guessing", the post link above has this photo of a disassembled light that shows where the base of the red lens sits on a rather thick rubber gasket-grommet.
It seems to me that if your gasket-grommet is rotted or missing it could cause the bulb to hit the top of the red lens? Just a thought (and a guess).
Looking through the red lens, can you actually see the top of the bulb hitting the lens?

The 12V #67 bulb works fine in my 12V converted M38 lights. I lucked out and got NOS fixtures so the gasket-grommets in mine are like new, which does mean that mating the bayonet (not the bulb bayonet, the fixture bayonet) is pretty tight to make. I used a little silicone lube on the rubber to help. Guessing again, I suppose that's why they made the red lens so thick and robust --- so it won't shatter easily under the pressure.

While I'm guessing, and assuming that you have good gasket-grommets, might there be a chance that you're mistaking the tight pressure needed to mate the fixture bayonet assembly for the bulb hitting the red lens instead? That big spring in the base is pretty stiff to overcome in order to get the bayonet to lock. At least it is on mine.

Good luck!

Mike_B · Post by **Mike_B** » Sat Oct 23, 2021 1:19 pm

Sometimes I feel like such an idiot...I took Wes's suggestion and pulled a bulb out of my M38 which has also been converted to 12v by the PO and found #67 bulbs.

I remesured what I have...

#67 = 1.369". This fits.

#89 = 1.413". This does not fit.

#1251 = 1.362 This fits, but is 24v.

I assumed the #67 wouldn't fit based on the specs which says it's 1.44", but the ones in my M38 do fit at 1.369".

Next time I'm at the parts house I'll buy new 67's and confirm they fit.

Mike B

Mike_B · Post by **Mike_B** » Thu Nov 04, 2021 5:14 pm

Just to close this thread out I picked up 4 new #67 bulbs at my FLAPS and they all measured 1.41". They all fit, but I believe they are right at touching the glass.

Moving on to the next thing...

Mike B

Post by **wesk** » Thu Nov 04, 2021 11:52 pm

Mike, Did you ever reply to Ron's question on the thickness of your lens gasket?

Mike_B · Post by **Mike_B** » Fri Nov 05, 2021 9:24 pm

No Wes, I must have missed that question...

The rubber gasket/seals were all pressed into the lamp housing/shell and I really don't want to try and remove them to measure them. Is that important to know at this point?

Mike B