Very Strange Grounding Issues on Mountain Aire

[ColoradoBnd]

I have been having numerous problems of late with grounds on my coach. As a first point: when I kill the chassis ground shutoff, I still have chassis power. I guess that is normal after talking to Spartan. I always thought this is where Newmar made their primary ground tie ins to the chassis, but maybe not. What I can say is there are lots of things on the coach that do not work when that shutoff switch is thrown.

Newmar was no help today, they said they do not provide electrical support. There is no way it is 12+ V when the switch is thrown because things work partially. Baggage doors won't actuate, but there is noise at the relay. Yesterday the stairs partially extended with the switch off and now it seems like the motor is done. I also lost the motor on the drivers side window. A month ago the baggage compartment locks quit and the shop ran a new ground and everything started working again. It is 13 years old, so maybe everything is just crapping out now, but it seems very coincidental.

Has anyone seen anything like this before? Could the switch be defective and not passing a full ground? Anything else?

["007"]

All your wiring and fusing you will find in this link with many links to your information.
The 12v link will lead you to the info.
You have a lot to digest on power, slides, motors and important links in link given to you plus the info from COM_NET for your coach.

[azSkier]

Our coaches are different models of the same year. They should be similar.

I am willing to try to help, but we need to clear up some misunderstandings.

1. Our coaches have two 12V systems; a chassis system and a house system.
The chassis system powers the engine, starter, steps, door locks... things that are typical for any vehicle.

The house system powers the 12v items in the house; slide motors, lights, water pump, toilet, etc.

The chassis batteries are 2 batteries wired together to give the starter enough power to crank the engine. The chassis fuses are located in the front compartment on the driver side.

The house batteries are 4 or 6 or 8 batteries connected together. The house fuses are usually located in the mid-bath area. There are additional 12V components located in the power bay. Way back behind a black, plastic panel.

2. There is no ground disconnect. Each system has a ground that is attached to the frame and also to the fuse block.

There is a house battery disconnect switch located above the driver's seat. Turning this on will provide power to the house. Turning this off will disconnect all 12V power to the house. The chassis power system is not affected by this disconnect switch. The switch itself is located behind the black panel in the power bay.

I am unaware of any chassis battery disconnect.

When you have any kind of 12V power problem, the first place to start is the battery terminals. Get some 200 grit sand paper and clean the battery terminal post and the inside of the battery cable terminal. It is a tedious job, but necessary... especially if you have standard lead-acid batteries.

The problematic items you listed are all on the chassis battery system. Find your chassis batteries and clean those terminals first. There is a black cable that runs from the chassis battery and connects to something; probably the frame somewhere. Try to find the end of that cable and clean that connection.

The chassis batteries will have multiple red cables that run to many different components. It is unlikely there is a problem there, so don't focus on those cables just yet.

[ColoradoBnd]

Thank you both. I cleaned up all grounds on battery terminals several months ago. I know that shutoff switch isolates many of the systems I am having trouble with. I wonder if I should clean those terminals? I wonder where Newmar pulls their grounds from off the chassis? Battery terminals or some other place?

Still don't understand how some voltage gets past that chassis switch when I know on my coach it does isolate some of the problem locations I am having.

[azSkier]

What are you calling a chassis disconnect switch?

["007"]

Ground cables go to chassis frame which is ground, this link explains more do not try to make it hard on yourself for simplicity..
You also may have a inverter supplying 110 off your batteries to other outlets off a different load center.

[ColoradoBnd]

I’m referring to the Spartan engine bay switch. I’m probably using the wrong name because I understand it doesn’t kill everything. But from trial and error I tend to know what it shuts off on my coach.

Here is another strange fact based on 007’s comment. When I try to check on frame parts like the bar that that disconnect switch is mounted to and check continuity to the battery ground - NONE. Thanks for the help help guys. This thing just defys most of my automotive experience.

["007"]

Wiring from that switch feeds to chassis ground and negative off your batteries.

[azSkier]

I am not familiar with this spartan switch. Would love to see a picture.

Trouble shooting a switch is pretty straightforward. Disconnect both cables from the chassis batteries.
Then use your multimeter to ohm out the switch in both the on and off positions. You should see 0 ohms when on and an open connection when off.

It does sound like this switch is bad and needs to be replaced. Spartan should have a replacement for you.

[ColoradoBnd]

Already ordered!

["007"]

The different BCO switch's in a coach.

PICTURES

A good thread for chasing down battery ground cables by Brucelica