Monaco Dynasty cranks then all goes dark

[Brad247]

My money is on a bad relay that energies the chassis

[YC1]

I'm with those suggesting a large cutoff switch has failed.

You voltage of 13.1 is useless without a load on the system and there is no way on earth it would be that while cranking the engine.

What sound are you hearing? It sounds like? With a helper you may be able to chase that but it could easily be an effect and not a cause.

Are you losing power to the dash etc after turning the key? I mean do they go away and then come back a short time later?

If you are losing a main power lead do to a bad switch for example the voltage may creep back through enough to engage a solenoid, thus your clunking noise sounding like a reset.

Sometimes it takes 20 questions to sort these symptoms out.

[handyt]

Originally Posted by YC1

I'm with those suggesting a large cutoff switch has failed.

You voltage of 13.1 is useless without a load on the system and there is no way on earth it would be that while cranking the engine.

What sound are you hearing? It sounds like? With a helper you may be able to chase that but it could easily be an effect and not a cause.

Are you losing power to the dash etc after turning the key? I mean do they go away and then come back a short time later?

If you are losing a main power lead do to a bad switch for example the voltage may creep back through enough to engage a solenoid, thus your clunking noise sounding like a reset.

Sometimes it takes 20 questions to sort these symptoms out.

The coach cranks for a short time then there is a single click and the starter stops and the dash goes dark. Then, after about 5 seconds or so, there is another click, likely from one of the automatic circuit breakers and everything powers back up again. Until I try starting it again when the cycle repeats.

[YC1]

Originally Posted by handyt

The coach cranks for a short time then there is a single click and the starter stops and the dash goes dark. Then, after about 5 seconds or so, there is another click, likely from one of the automatic circuit breakers and everything powers back up again. Until I try starting it again when the cycle repeats.

The coach cranking, assuming it is a good strong crank and can be repeated in a few minutes indicates the batteries are likely fine.

Losing power to the dash could be a breaker resetting. But as suggested, you still need to get some voltage measurements while cranking.

The batteries parallel several paths and the one to the battery would not likely go through any breaker. Starters draw hundreds of amps and a breaker would be an absolute monster.

A breaker feeding the coach dash would be much smaller. But large in a normal 12 volt world such as 150 amps.

You would not normally hear one reset but you could easily hear a large relay.


Are you connected to shoreline while doing this? If so that adds another dimension to the equation.

[Podivin]

Originally Posted by handyt

The cable connections are all very clean. I was very careful to clean all the corrosion and neutralize the acid on them before installing the new battery. The little crimp terminals were corroded and were replaced on clean wire.

Forgive me for belaboring a point, but did you do this to both ends of the cables or just the battery end? If only the battery end then it would still be worth double checking the other ends.

[handyt]

Originally Posted by Podivin

Forgive me for belaboring a point, but did you do this to both ends of the cables or just the battery end? If only the battery end then it would still be worth double-checking the other ends.

So I figured out what it was.
The rear power bay, there is a feed through stud that takes the output of the chassis switch and feeds it through the wall from the outside to the inside of the rear power bay.

Turns out that the cable hooked to the outside of the passthrough stud was loose. This caused a high current situation due to the loose connection which caused the voltage to drop which in turn de-energized the 12v relay coil that feeds the chassis power to the front power panel (outside on the driver's side). This caused the dash to go dark and since there was no longer any power through the key switch, the starter relay de-energized and craking stopped. After the power demand ended, the voltage went back to normal which re-energized the front chassis circuit and the dash lit back up. When it did, the key switch had power again and I was able to crank again until it all happened again.

Tightening that one connection fixed it. I also replaced all the continuous duty relays that run (hot) all the time as they begin to fail after a while too.

Aren't RVs fun??

[ElvistheKing]

Just seen you have fixed the 12v problem, what jumped out at me was 10s of cranking, not sure my engine(s) has ever needed close to that to start! Normally I'd say check the glow plugs but I understand the Cummins in mine, for instance, has heater grids on the intake.