Lost all power please help

I am having a strange problem with my 98 Bounder RV .
About 40% of the time when I  Try to  start the RV When I turn the key I find I have no power . No power to anything on The dash, back up camera, radio and most other auxiliary items.  Then after a while sometimes everything will turn back on. However sometimes I have to turn the battery disconnect off and on several times before it will turn back on . I am not sure if Turning the battery disconnect on and off is what is making everything turn back on. everything seems random. Has anything like this happen to anyone else? Does anybody have any advice on what to check? Any help Would-be greatly appreciated. 

The next time you turn on the battery disconnect and you don't have power, take a reading from each of the terminals to a good ground. You should read battery voltage on your meter on both. If not, you have a bad disconnect. If you do have power on both to ground, post back and we can go from there.

Check all your battery cable connections on both ends too. Make sure they're clean and tight.

All connection are clean and tight. The battery disconnect switch in the cab above the door are reading with the correct voltage

Sound very much like the chassis (engine) battery is not being charged or is at its end of useful life as all the things you mention are powered by that battery... The battery disconnect does not usually affect the chassis battery. But first things first,  follow the suggestions from kdbgoat and then, if necessary, replace the battery.

Your 98 Bounder should charge both sets of batteries if plugged in, or with the engine running but if not....

I was thinking the battery 2as dead but then when the power does come back on everything works and starts fine. It's like the battery is turned off then randomly turns on.

It sounds like a problem my friend once had with his Bounder. Finally tracked his problem
down to a loose power connection to his starter (at the starter). You might check that.

Would that cause all power everywhere else go out.

Is there  a way to bypass the battery disconnect solenoid

That solenoid does not affect the engine battery (in theory) if you are talking about the NORMAL battery switch. By-passing it would only make the switch ineffective for the COACH or House batteries. Some units may have a disconnect for the engine battery too but most don't unless one was installed by a previous owner.

What you will have to do is track down the voltage loss using a meter. Double check the ground connection (- side) for that battery, usually found on the engine block or frame. Disconnect, clean and reconnect.

Could you bypass the battery disconnect solenoid? Sure... Simply disconnect the heavy wires on each side of it and join them together or place a heavy jumper wire between the two terminals.

My motorhome, all my friends and relatives motorhomes have both chassis and house battery disconnects. Didn't realize we were a minority. Anyway, had the same problem once and it was the old nemesis, bad ground. Engine would start with the emergency button, or you could leave key on and wait 10 minutes or so and everything would light up. I theorized the bad ground would warm up a little and make connection. The bad ground was right at the battery post. Found it with infrared temp gun when everything was running.

Ok all batteries are fully charged i think battery disconnect it working right. Could the ignition cause a loss of power

Has happened to me ,many times.. I( will list the causess

1st time: When they built this Motor home they used the wrong type of connector on the battery Positive, the result, Corrosion.. Cleaned it and all was good

2nd time: Same as the first, a little bit faster and corrosion a little bit wose.

3rd or 4th time, Bad battery.. I also replaced the terminal connector with the CORRECT metal (lead)

Last time: It was the other end of the Negative cable, also replaced

Both bad connmectionds and bad batteries can do that.  I have a dual-meter load tester from Horrible, er, harbor freight.

This unit has two meters (Volts and amps) and a knob, supposed to be abl;e to adjust the load from just a few amps up to 500, only hit 450 on my best day.

It's very useful.. When the lug went bad at the engine end I hooked to the battery.. Dialed in 3x the battery capacity, and it passed.

Moved the negative terminal (I had disconnected the positive on the battery for testing, NORMALLY I disconnect the negative but I'd done that a couple days eariler)

Moved the meter's negative to the chassis.. NO VOLTAGE, and NO CURRENT

Moved to a Starter mounting bolt  Same result

Followed the battery negative to the engine, Wiggled and the meters jumped, It passed test again

DIAGNOSTIC (Bad connection, cable to engine)

Take the ground cable off the engine to the frame and clean them both. The engine is mounted with rubber mounts, so it has to have a good clean ground. Then fallow the ground from the battery to the frame and remove and clean it. If it is a GM the ground will be on the drivers side on the rear of the engine.

GM also has trouble with the ignition switch contacts. It is located low on the steering column, right side. Real easy to change and can be bought at any O'Reillys or Auto Zone. Here is what one looks like.
https://www.oreillyauto.com/detail/dorman-oe-solutions-3387/lighting---electrical-16777/ignition-switch-11887/ignition-switch/924872/4260948/1998/chevrolet/p30?q=igni

Uh, on my 8.1 Vortec the ground is on the passanger side.. Just so you know.

HOWEVER if you follow the big black wire... You get there No options. 

A Battery Disconnect for the Chassis battery used to be common and most all 90's vintage Fleetwood coaches had them. Newer ones usually do not. Diesel coaches usually have an "engine off" switch in the engine compartment to prevent it from starting, but it may not remove all chassis battery loads.

Assuming this Bounder does indeed have a Chassis Battery disconnect, that would indeed cause a total loss of power if it was flaky and made/lost contact internally. It can also drop out if the power source for the solenoid is intermittent or perhaps the voltage too low.  The solenoid usually can be bypassed by putting jumper cables on the big terminals that connect the battery cables. The smaller terminals are for the power that operates the solenoid.

Do not confuse the battery isolation solenoid with the disconnect solenoid. They often look the same and may even be side by side.

The '98 Bounder most definitely does have a battery disconnect solenoid.  It is located in the BCC (Battery Control Center).  The BCC is located on the drivers side of the firewall behind the front hood.  The solenoids are located behind the circuit board.  These solenoids are magnetically/mechanically latched, but can fail to make electrical contact internally like any other solenoid.  They are also susceptible to failure to latch (or remain latched).

Your symptoms could indicate a failing solenoid.  If the disconnect solenoid fails to make internal contact, when activated, the ignition signal will not be sent on from the BCC to the engine circuits.

A review of ALL your symptoms would help to isolate the problem to the solenoid or a possible battery connection problem.

The next time the problem occurs, check to see if you have headlights while the condition exists. 
If no headlights, then you have a connection problem closer to the battery.

If the lights still work, but the engine won't start and the dash doesn't light up, you probably have a solenoid problem.  You could bypass (jumper around) the disconnect or replace it with a new one.

Just for information, the disconnect solenoids and the isolator solenoid will look NOTHING alike in your Bounder.  Your disconnects will be black square units (photo #1) and the isolator will be the usual small cylindrical shaped unit (usually described as a Ford starter solenoid - photo #2)

Just wondering if you tried the battery boost switch to ty in your auxiliary batteries when you try to start and get nothing?
Bill