Joined: Jan 31, 2012 Posts: 197 Location: West Point, VA
Posted: Sat Mar 24, 2012 9:31 pm Post subject: Dash Light Box.
So I bought some parts today and two Dash Light box switches came with it. The guy said they may be burnt out but he wasn't sure. Is there a good way to check to see if they still work? I plan on taking them in to work and letting some avionics (helicopter electricians basically) guys look at them. Any way I can check this so they don't have to?
All you need is an ohm meter and patience and a copy of TM 9-1825E.
There are three basic type switches used through M38 production. Only the third type was used in M38A1 production.
The earl and mid switches were built by Bendix-Scintilla and were rebuildable and have a complete internal parts breakdown in the M38 ORD 9. The late switches were throw aways and although some makes could be opened, cleaned and closed again there were no replacement parts listed for them.
The switch pin-out below is all you really need to check operation of the switch.
For example you connect one test lead to the pin F which is power in to the switch. With the switch levers all off you should not get any continuity on any of the other pins. Now if you select service drive you should then have continuity between pin F and pins M, C, A & H. Also you should have continuity between pin K and pin C .
When checking the switch installed in the jeep this chart will help:
Pin Letters are raised in rubber disc. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jan 31, 2012 Posts: 197 Location: West Point, VA
Posted: Mon Mar 26, 2012 5:52 am Post subject:
Ok so out of the two I have, I think one is burnt out. The other one may be working as the avionics guy was getting readings on different pins depending on the setting. I figured it wouldn't hurt to try it out and see what happens once I get the jeep up and running. I guess the question is what do I do with the burnt out one? Big paperweight or just throw it out? Can anything be done to it to make is useable again?
Last edited by army_inc on Mon Mar 26, 2012 8:54 am; edited 1 time in total
Which model are the two switches? The two early model switches I posted above are serviceable. Those after that are throw aways. You can open some of the throw away types and try to clean up the switch contacts and lubricate them with the proper lube but most must be broken to open.
Quote:
The other one may be working as the avionics guys was getting readings on different pins depending on the setting.
Variations in Ohm readings is usually a result of burned and/or corroded switch contacts. That is probably why the switch is not currently installed in a jeep. That type of issue usually results in overheating of the switch and popping of the built in circuit breaker.
If you want long troublefree service get an early switch and refurb it or buy a NOS new production push button type which bolts in the same hole and uses the same plug.
Joined: Jan 31, 2012 Posts: 197 Location: West Point, VA
Posted: Mon Mar 26, 2012 8:50 am Post subject:
Well, I have the late switches that go into the A1 Both have screws in the back and look as if they were opened and possibly cleaned at one point in time. The guy I bought them from said he couldn't remember if they were burnt up or still serviceable.
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