No lights ! ( M880 )

Hi guys,

I am having trouble with my lights cutting out on my M880, when they go out they ALL go out and then come back on their own ( usually about after 5- 20 seconds )

I can find no problems with the wiring and the civy headlight switch is new. it does not seem to be vibration induced, the lights will even blink out sitting in the driveway with the motor off. they usually go out after they have ben on for a while
( a hour or so )

I have no clue how the Blackout lights inter grate with the civilian wiring so I am here looking for help.

1) what is the most likely cause for this condition ? I have read post where others have had the switch itself fail on M35s. is there a more likely cause on the M880 ?

2) does the power for the lights go to the 3 lever switch first before going to the civilian headlight switch or does it come from the civilian switch and then go to the 3 lever switch ?

3) If I have to replace the switch... will any 3 lever switch work or is the switch on the m880 different because of a 12v system ?

4) is it possable to jump the plug for the 3 lever switch to get it to run in service mode without the switch itself ? If so what pins do I need to connect ?

I would really like to see a wiring diagram for this but cant find one on the net. I know I can't be the first person to have this problem, any help or advice is really appreciated......

Many Thanks

Not sure how it's wired but it almost seems as though a self-resetting circuit breaker is operating. It will cut-out, or open when the load on it is too much, then reset after the load is shed. Is the light circuit protected by a breaker or a fuse? If it's a breaker, it may be getting weak, or it's the wrong amperage rating. Just an idea.

There is a 15 amp breaker that is wired into the fuse box between the turn and emergency flashers, I cant figure out what it is for because I can not find it on the civilian wiering diagram. it is however wired with civilian wires, not the black, number tagged wires that go to the rest of the B.O. system....

I can find no fuses for the B.O. system.

Not sure what it's for either. Fifteen amps seems weak for a lighting circuit but there may be a relay in the mix as well. One way to find out if it's for the lights is to turn the lights on then pull the breaker and see what happens. Hopefully someone else with an M880 will chime in.

I pulled the breaker in question and the lights still worked,

where can I get a NOS 3 lever switch ? I cant find them on Saturns web site....

One thing to watch on the M880 is the wiring harness connector block between the firewall. The pins will break or carode causing all kinds of electrical gremlins. A M880 I worked on once did the same type of thing you are talking about and that was the problem. Also bad grounds everywhere but I am sure you know this because you own one.

The M880 I drive for our Museum does the same thing-usually when the turn signal adds draw on the system for too long, like exiting the freeway or waiting at a light. I've been told the breaker in question is up behind the dash and next to impossible to get to. All the other breakers have been replaced at least once, and it still continues. Luckily, we don't do much driving after dark, so I've learned to be patient, they'll be back on in about 8 seconds.

Edit:
I never use the 3 lever switch, if that makes a difference. Don't know if the blackouts even work!

Hi guys,

Well after pulling the whole dash and spending about 6 hrs tonight looking at wiring diagrams and testing things.... we have come to the conclusion that the problem lies on the Blackout light system, we can find nothing wrong on the civilian side of the truck. That being said we are a little perplexed as to why there is a breaker and a relay that only seems to effect the running lights. ( for trailer lights maybe ? )

we suspect that the relay inside of the B.O.light switch is week but cant find how the system grounds out to completely rule out a poor ground. we do know that the condition is more frequent with the greater of load that is put threw the B.O.system ( high beams, horn and especially the emergency flashers ) and that the system re-sets itself after a few seconds....

I need to know :

1) how does the Blackout light system ground.

2) how do you get the Blackout switch apart ? is the relay in there replaceable / can they be rebuilt ?

3) there is another relay mounted under the dash. when it is unplugged everything still works,the wires are hot but some are labeled to be grounds for magnetos ?.

they are numbered : 7- Battery ground including master switch if in this circuit....11- ignition switch feed or magneto ground ( LH ).....12- ignition switch to ignition coil or booster switch to booster coil.... 13- magneto ground ( RH ) 12 and 13 are wired together.

I have no clue what this relay is and it does not make any sense to me. am I looking at the wrong " M-series vehicle circuit numbers " chart ? does anybody have any experience with this relay ?

This is the chart that I have : http://www.olive-drab.com/od_mseries_circuits.php3


Many Thanks,

Back some years ago the Fire Dept I was on got an 880 from the DNR for a brush truck. None of the lights worked right {Even using the 3 lever switch correctly}. I did a bunch of hunting around including a stop off at the NG armory {back b4 9-11 when you could just walk in and wander around until you found what you were looking for}. My search for a wiring diagram ended with this response. The M880 program was such an off the shelf-throw togather program, the trucks were shipped from Dodge to the gov w/o the switch. When a quantity of trucks was shipped to the unit, a simular quantity of switches were shipped to the unit. It was up the the unit motor pool to put them in as they saw fit. So there really is no connector to connector interface between the switch and the truck, it is just spliced in were that perticular motor pool mechanic found to work the best for him {this sounds like a job for the rookie}. I imagine that there was some bullitin somewhere that say patch switch wire 23 into the blue wire, ect, ect, but not the normal whole truck wiring diagram like we are used to. Back 15 -20years ago when '70's Dodge trucks were all that I drove I could help you on the civi end, but that knowledge was evicted from my brain a long time ago.

N1265, any luck?
Does this happen with both the service lights and the blackout lights, if not which one?

Did you refer to Chapter 25 of TM 9 -2320-266-34?

The BO lights work, but we do not know if the the system will kick out if only running the BO lights...

we do know that when the lights go out you can hear and feel a click in the BO switch,
( in service drive ) and everything that is controled by the switch turns off : lights,flashers,turn signals and horn. nothing else is affected ( like the blower motor or windshield wipers ) you can also hear and feel a click in the relay just to the right of the fuse panel witch is suppose to be wired in to the parking lights, we suspect this relay is extra protection in case you have a lot of draw on trailer lights ( But not 100% sure at this Point )

we also know that when the lights turn off there is still power from the fuse box to the BO switch via wire #5 therefore we suspect the switch being bad but want to make sure the grounds are in order before ordering a new $75 switch.

I have just found the TM you suggested and I am waiting on my Lil brother to come up here and take a look at it. but so far everything I can see looks right ...

(except I don't think they wired the the panel side of the BO light switch up)

does anybody know if you can get these relays at radio shack ? being 30 years old and having the dash apart I would like to replace them now.....

Sounds like there is a relay, or circuit breaker inside the three lever switch as you thought. I guess the next step would be to see if the BO lights go out as well, but they may not draw enough current to do that. I don't think RS would have that heavy duty enough of a relay but an auto parts store should since the parking light relay is original equipment.
Chapter 10 in that same TM has the wiring diagram for the service lights and BO lights.
Also, I saw www.forjeepparts.com had a switch (MS51113-1) for $60.