problem with all lights

[gsxrinthe9s]

76 dodge ambulance having problem with all lights going off then back on after about 30 sec then back on and off again. not sure where to start looking

 

[Flyingvan911]

Find the ground points and clean them. Check the fuse block for loose wires and contacts.

 

[N1265]

If equipped with blackout lights, the switch has an internal thermal circuit breaker. Something is causing it to trip and as posted above cleaning the grounds is a good place to start.

Also check to see if the factory wiring has been hacked into, sometimes the factory turn signal switch goes bad and people will start hacking into the wiring to get lights to the back of the truck.

This condition can be fixed, but depending on how bad the problem is it may cost some time and money.

 

[gsxrinthe9s]

yes it does have the black out switch. and theres been another devolpment it seems if i dont disconnect the battery when the truck isnt being used for say a week or two the battery goes bad and cannot be recharged

 

[NDT]

My guess is a weak circuit breaker inside the 3 lever light switch.

 

[gsxrinthe9s]

thanks for all the sugestions i will start on this the next semi warm day. but i have been thinking im not sure the circuit breaker being bad would make the battery discharge when not in use would it ? but what ever is overloading the circuit breaker could be whats causeing the battery issue. whats you guys thoughts

 

[N1265]

i have been thinking im not sure the circuit breaker being bad would make the battery discharge when not in use would it ? but what ever is overloading the circuit breaker could be whats causeing the battery issue. whats you guys thoughts

This is true, to a point. These issues may or may not be related. The circuit breaker may be being tripped simply because of its age. A "weak" circuit breaker by itself should not cause the battery to go dead, but it will cause all the lights to keep going off and on by itself like you described.

However, if there is a short somewhere inside the blackout switch itself, it could cause the battery to go dead.

Power comes from the bottom side of the fuse panel and goes to the main blackout light switch, then it is distributed from there. The power for EVERY light bulb on the truck and also the horn runs threw that switch FIRST. Also, there is no circuit protection between the fuse panel and the internal circuit breaker inside the blackout light switch . (This only applies if the truck is wired as it is suppose to be, many of times this wiring may have been altered and hacked into by a previous owner trying to get the lights to work )


Keep up posted and good luck .

 

[Bob H]

A M886 I had would drain the battery after a few days, never did figure that out.
(Although I never really tried) I just always disconnected the battery.

Need to check connections, power wire rubbing on metal with bad insulation is a possibility.
I have several of these trucks and found over 90% of electrical issues are ground related. I did have a 3 lever switch go bad on my plow truck.

 

[citizensoldier]

This problem could also be the firewall connections. Pull that apart and inspect for corrosion and broken pins. It will make all kinds of ghosts appear in your truck..

 

[Bob H]

Thanks Lane, I missed that one. There is a thread on here somewhere about that firewall connection, complete with pics and all. Unfortunately I have zero search luck here.

 

[Camofuel]

I have had Similar lite problems on 2 M880s and ended up being bad Blackout lite switches.

 

[citizensoldier]

I had that problem with one truck here and the Museum truck had a real bad problem with that. You would be driving down the road and the truck turned into a Christmas tree.