Joined: Jun 17, 2012 Posts: 159 Location: Minnesota
Posted: Fri Jun 29, 2018 6:47 am Post subject: Light Switch Repair
I see there is a download for repair of the 24V light switch. Has anyone tried this? What are the difficulties? Within probability of the average home mechanic? I would like to keep my original switch if it can be repaired. Thoughts?
Thanks.
Dan _________________ Dan Schultz
MD20035 9/1952
MC70324 dod 6/52
GPW 14944 dod 4/10/42
K38 Linemans Trailer 4/43
M100 Trailer 01177488 dod 8/51
I'm investigating having some rotors made for the early repairable switch. Nothing to report yet. _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Joined: Jun 17, 2012 Posts: 159 Location: Minnesota
Posted: Fri Jun 29, 2018 7:56 am Post subject:
Good post to look thru. Is the rotor the typical problem. It seems mine rotates fine, but only has dead circuits. Thanks for the help. _________________ Dan Schultz
MD20035 9/1952
MC70324 dod 6/52
GPW 14944 dod 4/10/42
K38 Linemans Trailer 4/43
M100 Trailer 01177488 dod 8/51
Joined: Oct 02, 2014 Posts: 2059 Location: South Carolina, Dorchester County
Posted: Fri Jun 29, 2018 9:18 am Post subject:
Dan,
I don't know for sure if the rotor is a typical problem, but would tend to say yes. Not a lot of feedback or experience forthcoming from the forum members. The rotor is a vulnerable moving plastic part. One of two pieces of plastic in the entire switch (the other piece is solid and pretty much fool-proof). Of the 7 switches I have, 6 have broken rotors. It's easy to see why --- looks to me like the rotor breaks when the locking lever either isn't used or when it's not fully disengaged (ham-handed operators). Heck, it might have been purposely designed that way for all I know. Making new rotors out of practically unbreakable Delrin might inadvertently inject a different failure (even harder to fix than replacing a 25-cent rotor).
Only one switch I have has a burned (arc welded) contact. If what I have is typical, this tells me the majority of problems with the switch are mechanical not electrical. But I only have these and my limited exposure to go by. The switch is fairly simple and comes apart pretty easy. While it has some spring-loaded contacts and a ball-bearing, nothing will fly apart when you open it up. See for yourself.
One thing for certain, without a replacement rotor the switch is down hard. No way around it. I'm hoping I can get some made for a reasonable cost so at least some switches can be resurrected from the dead.
There doesn't seem to be old stock of any repair parts for these switches in the market. Other repair parts would also have to be scrounged or fabricated. _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Joined: Jun 17, 2012 Posts: 159 Location: Minnesota
Posted: Fri Jun 29, 2018 1:46 pm Post subject:
Thanks a bunch for the help. I hope you are successful with the rotor project, it seems like it would be a great help to the hobby. Keep me in mind if you are successful.
Dan _________________ Dan Schultz
MD20035 9/1952
MC70324 dod 6/52
GPW 14944 dod 4/10/42
K38 Linemans Trailer 4/43
M100 Trailer 01177488 dod 8/51
Dan, note the mention of the repairable early switches. Only the two Bendix style switches are covered by the TM 9-1825E I posted. All the 52 & up switches are not repairable and were always considered throw-aways.
Joined: Jun 17, 2012 Posts: 159 Location: Minnesota
Posted: Sat Jun 30, 2018 6:31 am Post subject:
Well, that makes a big difference. I definitely have the latest version. If I find it defective I will have to find a new one. I see that several of the vendors have them. Not too badly priced. Thanks for the help Wes.
Dan _________________ Dan Schultz
MD20035 9/1952
MC70324 dod 6/52
GPW 14944 dod 4/10/42
K38 Linemans Trailer 4/43
M100 Trailer 01177488 dod 8/51
A few of us over the years have tried repairing the newer units. As you can see their cases are joined in a way similar to instrument cases in that the edges are crimped and attempts to release the crimps and later recrimp always end up poor looking to say the least. Once inside you'll find the damage but you won't find any parts out there on the market. I decided several years ago that when & if my switches fail I'll probably replace them with the bolt in new style units that are push button types. Although a bit more expensive you run less risk of internal moving parts failure but these are also throw away units.
I have seen them much cheaper. Reliability issues are more applicable to earlier, pre 2005 issue units.
I would advise folks to shop carefully and use quality vendors.
Here's some links to more defined data:
Quote:
Push Button M-Series Light Switch
In April of 2002, TACOM and the Defense Supply Center in Columbus, Ohio began a retrofit program to replace the standard three lever light switch on American M-Series military vehicles with a new design based on electronic push buttons. The new switch was required due to maintenance problems with the old, mechanical switch plus the fact that it had no illumination at night.
Push Button M-series light Switch Assembly
M-Series push button replacement for the 3-lever light switch.
Replacing the M-Series 3-Lever Light Switch
The revised M-series light switch pushbutton design, pictured above, is a direct plug-in replacement that can be installed in any existing MV that used the 3-lever unit. The coupling on the back of the push button switch is the same MIL-C-28-51 connector as on the 3-lever switch.
Here is a photo of the new and old switches side by side:
Push Button M-series light Switch Assembly
The NSN and description for the push button switch is 5930-01-491-9893, Blackout Switch. The manufacturer is Advanced Input Devices (CAGE code 59666) P/N 9375-00117. In some documents the switch is not called "Blackout Switch" but rather is just "Switch Assembly".
There were reports that early production of the pushbutton switch had problems and those units were not reliable. Get a guarantee from any vendor that you will receive a unit from newer production. By 2005 those problems seemed to be solved.
Download the Pushbutton Light Switch Instruction Sheets
The switch comes packed with two pages of instructions and drawings. Click to download:
The Army provided a work around for the earliest Bendix two plug switch back in the late 50's by just moving the wires in the small plug to their appropriate pin position in the large plug so any of the M series light switches made by Bendix thru 55 and any post Bendix M series light switch is easily replaced by the newest push button switch. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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