When the lights go out ...

sunsetoutpost2 · Post by **sunsetoutpost2** » Tue Jun 09, 2009 10:16 am

My lights (headlights and dash) go out for about 30 seconds intermittantly. I thought the circuit breaker might be at fault and jumpered it with no luck. Is there a circuit breaker built into the light switch?

GregL · Post by **GregL** » Tue Jun 09, 2009 1:19 pm

I've had the light switch assembly apart before, there's no breaker in there. BUT, I didn't have any dash lights when I bought the truck, turned out to be dirty connections inside the light switch. According to the M37 wiring diagram, there is nothing common between the dash lights and the headlights other than the switch itself. I know this sounds obvious, but have you tried repeatedly exercising the switch levers? If you have, maybe your light switch is bad, or what feeds the light switch. Do the rest of your lights go out too? You might also double check the ground connections at both the headlights and dash lights, even though they are not common.

Juan · Post by **Juan** » Tue Jun 09, 2009 2:44 pm

Do you hear a ticking sound every time the lights goes off/on?
If you hear it, then a circuit breaker is doing it's job, you are probably trying the wrong breaker.

sunsetoutpost2 · Post by **sunsetoutpost2** » Thu Jun 11, 2009 5:42 pm

Must have been a bad connection in the light switch or power to the swithc because both the dash and headlights would go out. Has not happened for several days now. Road vibration helps, the more driving the better!

knattrass · Post by **knattrass** » Fri Jun 12, 2009 7:56 am

We had a flicker in the headlights come/go - found that the connection to the dimmer switch was loose. Did not notice the i/p lights thou.

sunsetoutpost2 · Post by **sunsetoutpost2** » Thu Jul 02, 2009 12:05 pm

Found the problem. Waited till the lights went out, turned off the engine, heard a click when they came back on, felt a vibration in the light swithc. Took the light switch apart and there was a circuit breaker. Must be some have and some don't. That explains my 37s only having one external circuit breaker and the wiring diagram showing four. I soldered a wire across the internal breaker, added the external and problem solved.

MSeriesRebuild · Post by **MSeriesRebuild** » Fri Jul 03, 2009 5:22 am

sunsetoutpost2 wrote:Found the problem. Waited till the lights went out, turned off the engine, heard a click when they came back on, felt a vibration in the light swithc. Took the light switch apart and there was a circuit breaker. Must be some have and some don't. That explains my 37s only having one external circuit breaker and the wiring diagram showing four. I soldered a wire across the internal breaker, added the external and problem solved.

All the older light switches that could be disassembled had an internal breaker originally. The later sealed switches also have one, however when it malfunctions, the only fix is a switch replacement since it's a sealed unit.

So, evidently on Greg's some one had been in there prior & removed the breaker from his switch. There is just no telling what you may find when you start exploring around a truck.