M38 Headlight Problem

KHH37435 · Post by **KHH37435** » Sun Jun 30, 2013 9:47 am

The headlights on my M38 abruptly quit working. Tail lights, brake lights, and black out lights all still work fine, and the headlight grounds are good. There is no power out at the headlights. Before I remove the dimmer ditch or light switch to test them, does anyone have any suggestions on what the culprit might be? The repair manual states there is a circuit breaker for the light circuit behind the instrument panel, but the wiring diagram doesn't seem to show one - maybe I've missed it. Location of the circuit breaker if there is one? Thanks.

Post by **wesk** » Sun Jun 30, 2013 10:27 am

All depends on what serial number M38 you have and even if an early serial which came with a separate CB on the inboard side of the cowl battery box it may have been updated by the service or a civvy owner to no separate CB's.

Older units use the early Bendix-scintilla light switches. These did not have a breaker inside the switch but utilized one of the three breakers on the inboard side of the cowl battery box. There was an additional breaker on the instrument cluster. Later M38's dropped the four circuit breakers and only have one breaker inside the later style switches.

These are all automatic breakers. That means as soon as the overload goes away or the CB cools down it will reset.

The problem you describe indicates no power to either hi or lo beams at the headlights no matter what position the switch is in. It would help with troubleshooting if you tell us which wiring and switch you have.

Early

Late

These are the three style switches used. Left is the early switch with a separate plug feeding the trailer receptacle on the rear quarter. The middle was the transition unit still a Bendix-Scintilla unit that was used with mid serial that still had the 4 CB's and the left one is the generic late model switch made by several companies which was a throw away unit (not rebuildable). Any switch will work in any date M38 but you should always use the switch with built in CB on M38's without the 4 separate CB's.

KHH37435 · Post by **KHH37435** » Sun Jun 30, 2013 11:53 am

Thanks Wes. My light switch is the one on the far right with a single feed coming straight out of the back. My serial number is GB122870, dated 4/52 on the serial plate and the patent plate number is identical. So what is a "GB" vehicle? It certainly doesn't seem to be an M38 with a GB in the serial. It's a 24 volt waterproof ignition / system and everything else to me seems to be an M38.

Post by **wesk** » Sun Jun 30, 2013 12:02 pm

Those numbers are not M38. You don't have your location listed in your profile. Let me know where you are located. Post or email me photos of your jeep all four sides, the dash, the engine compartment. Or if you like you can load photos of your jeep here on our photo album page in your own album:
http://www.willysmjeeps.com/v2/modules. ... _album.php

KHH37435 · Post by **KHH37435** » Sun Jun 30, 2013 12:57 pm

Wes:

I'm located in Salina, KS (67401). I just posted some photos of the jeep. Thanks for your help.

Post by **wesk** » Sun Jun 30, 2013 1:44 pm

Well you definately have a M38. That patent plate is an aftermarket blank that was stamped by a previous civvy owner or state DMV. The dash plates were probably a surplus set often found at various surplus vendors and they were unstamped. My guess is a previous civvy owner had the vehicled titled as "Assembled from spare Parts" or "Owner Built" and that DMV assigned that VIN number. Or many DMV's used to use the engine number on titles and someone may have got the new tags to list the engine serial. What is your engine's serial number on the small flat above the water pump?

Do you have circuit breakers mounted on the back side of the instyrument cluster and the inboard side of the cowl battery box?

KHH37435 · Post by **KHH37435** » Sun Jun 30, 2013 2:05 pm

The engine serial number is 3J175783 and the block casting is 908758, which is obviously not an M38 block. The dash serial plates all have the same rivets and look like they are original to the vehicle but they may have been installed many, many years ago.

I don't see any circuit breakers anywhere near the cowl battery box but I haven't removed the instrument cluster to see if their are CB's there. I assume that's the next step I should take?

Xamon · Post by **Xamon** » Sun Jun 30, 2013 3:36 pm

I believe these are the circuit breakers, right on the side of the battery box.

Post by **wesk** » Sun Jun 30, 2013 6:44 pm

Those data plates are riveted to a screw on plate. That screw on plate takes 1 minute to remove and replace. Those data plates are assuredly not original to that M38. As I said earlier in the 70's and 80's those data plate sets that were ordnance spare sets were surplussed out by the hundreds and many military jeep wannabe's used to buy them and stamp their numbers on them and try to pass the CJ as an M38. If the number on your two plates match the number on your registration and title then my money says a prior civvy owner bought the jeep with no plates and made an application to the state DMV for a title using a state assigned VIN.