92 Fleetwood Bounder only starts with aux boost

This is what mine looks like. I have one for chassis and one for coach batteries.
Battery disconnect

Just remember that having voltage does not equate to having full power. My power solenoid( activates when ignition is turned on, had pitted and worn contacts inside the case. They would read 12.xx but would not carry the amperage needed to start the engine. As stated, clean terminals first, then test and eliminate bad parts.

Get the battery load tested, most chain parts stores will do it for free. That can show a lot.

"solenoid" are many times called different things. Solenoids can be called relays or in this case battery disconnects.
The silver ones are normally electrically held relays(solenoids)

enblethen wrote:
I would suggest you have a helper operate the battery disconnect switch while you listen for their location.

I have done so and they are what I am calling solenoids under the control panel. Am I missing something?

I would suggest you have a helper operate the battery disconnect switch while you listen for their location.
I was guessing that your Bounder has same layout as my Pace Arrow. Batteries in front of radiator? Follow the main battery cable to disconnects?
Is there a wiring diagram on inside of cover?

enblethen wrote:
Yes the battery disconnects are the solenoids. The brown ones are the disconnects. the silver ones are the ignition and the charge relays.
No, you need to connect one lead (black) of meter to ground, connect the other (red) lead to a large terminal. Best to start with the lead going to battery. It should have the same voltage as battery. If it does go to the other large terminal. If solenoid contacts are closed you should have same voltage.
The brown relay are mechanically latching relays. The small terminals from the electronics have the 12 volt DC reversed to open and close.

I only have two silver ones under control panel. Have pictures but don’t know how to post them here.

Miked9606 wrote:

Correct understood. Put a charger on it and is at 100%

That means virtually nothing. A worn out battery typically WILL show fully charged like that but then not be able to produce any, or enough, useful current.

You need a voltmeter.....to check the battery with the ignition ON.
And as said, sometimes connections that look clean and tight really aren't. In that case, the voltage on the actual battery posts would be different from the voltage on the connectors attached to them.

Yes the battery disconnects are the solenoids. The brown ones are the disconnects. the silver ones are the ignition and the charge relays.
No, you need to connect one lead (black) of meter to ground, connect the other (red) lead to a large terminal. Best to start with the lead going to battery. It should have the same voltage as battery. If it does go to the other large terminal. If solenoid contacts are closed you should have same voltage.
The brown relay are mechanically latching relays. The small terminals from the electronics have the 12 volt DC reversed to open and close.

The Aux switches just parallels the Chassis and the Coach. it does not replace the Chassis.
Now you have to understand why a chassis battery will not start the engine, and yet when you parallel them it does.

gbopp wrote:
Make sure your battery terminals are clean amd tight. Our 96 Southwind will not start if there is a little corosion on the terminals.
Take them off and clean them, don't just look at the terminals to see if they're clean.

X2

And follow the battery cables and check the connection where it goes to the chassis and solenoid.