M38 gauges and speedo, emitting light or not

MajBen · Post by **MajBen** » Thu Jun 16, 2005 3:20 pm

Hi, I am trying to determine if the 4 gauges and the speedo on an early M38 used phosphor to emit light.

If one checksPage 221 (Fib 83) of 8012 and Paage 174 (Fig 70) of 804, they appear to be clear, not having luminescence. Actually 804 is more applicable for my Serial No. 22797 than 8012 but 8012 is a better picture.

I have several old ones for the gauges and speedo. All of these except one is luminescence which goes counter to how the pictures look. Does anyone have any literature or other reference that might spell our the answer to this question. I will appreciate your help. Semper Fi Ben
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Semper Fi Ben

Post by **wesk** » Fri Jun 17, 2005 9:19 am

Ben,
I cannot discern with any accuracy weather the gages have luminescent coatings or not from the artwork in the TM's. This is artwork and not actual photos in the TM's. Actual photos were the basis for many of the illustrations but they were touched up by the illustrators. I would assume that thru the early 50's most if not all military gages came with luminescent dials of some sort. Mostly radium. These were attrited out of the system in the late 50's on when they were identified as hazardous material. Based on that I would say an accurate factory resto will have luminescent dials. I would also say an accurate motor pool resto for the period 1950 thru 56 would have luminescent dials.

Keep in mind that these dials were found to be hazardous to folks that handled hundreds of them a week like manufacturers and repair shops. You weren't going to be made sterile and mutated by sitting in your jeep looking at them. So there would not be a blood letting in 1956 making all of them instantly disappear.

Rick_L · Post by **Rick_L** » Fri Jun 17, 2005 10:04 am

For what its worth, the needles on my speedometer, temperature and fuel guage glow after being exposed to light in a dark garage. But its only the needles that glow.

MajBen · Post by **MajBen** » Fri Jun 17, 2005 11:28 am

Hi Wes and Rick for your come back. Rick can you be a tad more specific on 'guage glow after being exposed to light in a dark garage'?

Wes, You have a really good grasp of what was happening in the 50s and 60s with motor vehicles and I respect it- and appreciate getting an insight--if I decied to have mine redone, and it is a very expensive deal, I will have the luocent applied. Mine have it now but it has disiipated as far as glow is concerned and those places where it was originally appplied have turned brown---but otherwise they look good. Thanks guys. Wes I am writing you more directly

Rick_L · Post by **Rick_L** » Fri Jun 17, 2005 11:40 am

Sure. If I shine a flashlight on the guages for a minute or so at night, and turn out the garage lights, the needles glow in the dark, kinda a luminesence greenish glow. The panel I have has a circuit breaker on the back of it on the left side, don't know if that helps date it. The insturments look like they have been it for a long time.

MajBen · Post by **MajBen** » Fri Jun 17, 2005 11:55 am

Hi Rick, well I'll have to try that approach, thanks for sharing. You apparently have an early M38; I am not quiet sure when they changed but I have the circuit breaker there also and mine is 22797 Jun 51. There is also bracket on the other side to secure two connectors. Semper Fi Ben

Post by **Ryan_Miller** » Fri Jun 17, 2005 9:18 pm

Ben,

The circuit breaker behind the dash was eliminated late in M38 production (1952). Look at that list that is at the back of the document I sent you back in January.

I would either have the lumeniscent redone or not have the dial faces repainted at all and just have the insides checked out.

Post by **wesk** » Fri Jun 17, 2005 10:48 pm

The three 95 Ohm resistors were deleted at serial MC17856 abot MAR?APR 51. The Circuit breaker on the instrument cluster was deleted at MC65043 APR 52.

Post by **Ryan_Miller** » Sat Jun 18, 2005 7:10 am

Wes,

since I am at work and do not have the info handy, I think you meant that the three circuit breakers on the cowl battery box side were deleted from factory production in 52, not 51.

Post by **wesk** » Sat Jun 18, 2005 7:26 am

No. I meant the three 95 ohm resistors that attach to the oil press, water temp and fuel gages. The 3 cb's have nothing to do with the dash instruments. I don't want the two to be confused with each other which is why I didn't bother to mention them with the instruments posting. Again for everyone the 3 CB's on the battery box have nothing to do with this discusion on gages and the instrument cluster.

MajBen · Post by **MajBen** » Sat Jun 18, 2005 2:33 pm

Hi Wes and Ryan, I still want to kick this dog some more (excuse me Ryan). Monitor me and see if I have it right:

1) There are 3 circuit breakers that attach to the battery box. They have nothing to do with the gauges and are still there for the entire M38 production.

2) FUEL, OIL PRESSURE AND TEMPERATURE gauges of the early M38 had a resistor that attached to theoutside of the gauge. Page 175 of 804 and Ryan's reference manual Page 84 have good pictures of this type of gauge. (For reference for others who might be interested in this subject)

3) I am curious as to the documentation which SPECIFICALLY eliminated these gauges with the outside resistorsat at serial no. 17855.

Ord 9 1955 shows SPECIFICALLY that the WATER temperature gauge has a different Ord and Manu Number #17855. (However, cautiously I point out that there is no specific mention this change elimiationed the outside resistor---although it think it can be logically assumed that this was the reson for the change.)

4) The FUEL and OIL PRESSURE gauges listings in Ord 9 1955 have no mention of the serial no. where the new Ord and Manu #s were made for these instruments; it follows that there is no specific mention of the elimination of the outside resistor.

5) I question then why there is no specific showing for the serial no. change in Ord 9 1955 for the FUEL and OIL PRESSRE gauges simiilar to the FUEL gauge; throughout Ord 9 1955 listing are found with these detailed changes for similar items.

6) Do either of you know of any other documentation in this regard? This has been very confusing to me and I have had to really push the envelope trying to make some consistent sense out all of these numbers.

I am extremely happy that Wes made his posting and that Ryan made his as it made me take another look at these 3 gauges. Until these posting were made, I have been searching for a FUEL gauge with an AC No. of 1517270 as that is the number shown in Ord 9 1951 and when it is repeated in Ord 9 1955 I thought it still pertained to the early M38s with no consideration of the where the resistord was and that the top number 1517561 shown was for the later M38s. Likewise for the OIL PRESSURE gauge, I have been searching for an AC No. 1507491 and not AC No. 1507680.

If I have all of this straight, I am elated to learn that I have the correct gauges on hand and that the numbers I have been searching for had the outside resistors. Dumb me, probably, but you already knew that, but I think that Ord 9 is really confusing in this regard. As it seems, you two have had this already figured out but do you have any concrete documentation other than assumptions?

Thanks for your patience and help. Semper Fi Ben

Post by **Ryan_Miller** » Sat Jun 18, 2005 3:05 pm

Wes,

Sorry, I misunderstood the circuit breaker vs resistor terminology.

Ben,

The is also a listing for a change in the gauges at page 149 of the SNL G740 for :
Case, gage resistor, w/TERMIINAL and RESISTOR, assy (used on vehicles through serial No. 17855) AC-1507502 WO-118922

Also on page 153 (ORD 9 SNL G740 1955) the resitors are listed as being deleted at the same vehcile serial number.

Although it does not list a specific gage, this in relation to the 2 temperature gage listings and the presence of NOS 1951 dated gages without the resistor (that have the correct ORD 9 part number painted on the gage face and douglass metal connectors) make me believe that these references are to all three gages.

Again, further research with what little factory records exist could possibly spell it out more clearly.

Factory record research is not easy to come by and sources are limited. It all takes time and money.

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Post by **Ryan_Miller** » Sat Jun 18, 2005 4:11 pm

Ben,

I forgot to mention that on the listings for the resistor deletions has a quanity listed.

The quanity of resistor cases and resistors deleted was 3. The number of gages that had an external resistor is 3.

That also leads me to believe that only the very early M38 had the external resistors mounted.

MajBen · Post by **MajBen** » Sat Jun 18, 2005 4:15 pm

Hi Ryan, thanks for your reply. You have me completely stumped with the reference to the case---I had not noticed it before. What is that critter? I'm looking at your picture on page 84??? From the picture of what you have labeled 'External resistor removed from the housing,'as a side, it appears that the Douglas is a male connector whereas the one installed on the gauge appears to be female but both may be male.

Back to the main issue, if this 'CASE' is something related to the outside resistor type gauges, then I think you have it nailed as it apparently has no usage on M38s after 17885 and it calls for 3 of them. I hope this is the case and I can put this subject to rest.

I have learned a lot today, teach me some more.

Semper Fi Ben

Post by **Ryan_Miller** » Sat Jun 18, 2005 4:19 pm

Ben,

I hope I did not sound irritated at you as I am definitely not!

I had researched this subject 6 or more months ago and had apparently not written them down clearly and you have brought that to my attention.

I think that is fairly definite proof for me anyway.

Anyone else is welcome to jump in with any thoughts on the matter.