HELP - No 12 Volt House Current

[Don White]

Good Morning, 

All of the multplex switches in the coach have stopped working.  I attempted to turn on one of the 12-volt house lights this morning and heard a click from one of the Intellitec boxes and all the 12 volt switches went dead.  There is no power to any of the intellitec boxes. 

All of the 110 circuits are working fine, outlets, tv, etc.  When I turn the ignition key to the on position all the dash lights come on and buzzers sound.

The inverter appears to be working fine, the status light blinks green every 5 seconds and batteries are charging.  I checked the fuses in both front and back run box and they are fine.  I am getting current to both run boxes, 12+ volts.

Any suggestions on where to start tracking this down?

Thanks,

Don

[Fred Cook]

Check your house battery disconnect switch next to the batteries. Mine went bad and caused the same problems.

[Steve Huber Co-Admin]

Don,
There is a Multiplex CPU fuse in the Multiplex control box. It is F9 in my unit.
Steve

[Fred Brooks]

  Did you accidently turn off the battery switch at the entry when you tried to turn on the lights?

[Don White]

Hi Steve,

Is the multiplex control box the same as the PMC Central Processing Unit or something different?  If there the same I checked the 10 and 5 amp fuses and both are good.

Fred, the light switch I turned on and Coach Power switch are in different rooms so no luck there.

[Fred Brooks]

 There is an excellant trouble shooting guide in "coach assist" under multiplexing systems. Fred

[Don White]

Thanks for pointing me to Coach Assist...should have gone there first.

Thanks again.

[Don White]

Fred,

I have been able to determine there is no power getting to the power bus that feeds the CPU model and all the other modules in cabinet with the CPU model.  I have included a picture of the power bus below.  The large cable snakes up the back of the cabinet it is in into the roof.

Do you know where the 12 volt power to the power bus is coming from?  Is it one of the run boxes or somewhere else?  I have checked the wiring diagrams I have for the coach and haven't seen any diagrams that indicate where.

Thanks.

[Scott Shearer]

Don,

The domestic power buss is fed from the rear run box.

There are several large lugs at the bottom of the RRB. Looking from left to right,
Lug #3 is the input feed from the house battery bank.
Lug #7 is the output feed to the domestic power buss.

The path is; lug #3 to the right-hand terminal of the big boy, to the high-amp circuit breaker, to the number 1 ‘salesman’ solenoid, to the #7 lug

See image below.

-Scott

[Don White]

Problem solved. 

I tracked the lack of power to the multiplex to the rear run box and the coach power solenoid in it.  It supplies dc power to a distribution bus which is what the multiplex system runs off. The 5 amp fuse on the coach power solenoid had blown so no power.

Replaced the fuse and all is good.   Not sure why turning on a light in the bathroom at 3 am would cause it to blow, keep my eye on it.

Thanks to the 2 Fred’s, Scott, and Steve.

Don

[Joel Ashley]

Wouldn’t such a fuse (I don’t see one on our solenoid diagram) protect only the small gauge circuit through the “salesmen’s” switch at the door?  As problematic as those switches can be, perhaps the blown fuse is due to a short in it, or perhaps in the solenoid itself.

Joel

[Don White]

Hi Joel,

The fuse is located at the right top of the solenoid.  Please see the attached picture.  Regarding the rest I don't know.  This project has been a learning experience for me.  I have noticed that the solenoid is beginning to hum which it didn't before I started having the problem of losing 12 volt power.
 
It happened again twice of Thursday, but no blown fuse.  Pulling the fuse and reinstalling it seemed to “reset” the solenoid.  It has not happened again. 
Iam going to pick up a spare solenoid to have available in case it does finally go south.

Thanks!

[Don White]

Hi Joel, Sorry, the fuse is not on the right side of the solenoid but is on the left side.  Pretty embarrassing.  Of course shortly after posting my previous post the 12 volt went out.  Fuse was fine.  Banged on the solenoid with a wrench which appears to have got it working again...for now!

On to searching for a solenoid sooner rather than later.

Don

[Joel Ashley]

Well, reckon that pretty much zeroes in the need to replace a bad solenoid. 😉

Internal contacts are likely burned/corroded and offer too much resistance.