Community Forums

TexasBounder · 03-24-2015, 08:10 PM

My Aux battery switch that let's the coach batteries fill in for the dead chassis battery is not working. Can anyone tell me your experience with this and what things I should check first. Is there a solenoid that switches the batteries? Any help to steer me in the right direction would be appreciated

2004 Bounder w / workhorse chassis

Thanks, Bill

mahon1993 · 03-24-2015, 08:31 PM

A few things, usually the switch must be held down constantly to work. It is only a temporary emergency type of operation. So you hold the switch down while you crank the engine. There is usually a solenoid that the switch operates. It could be bad. And finally, the solenoid might have a fuse associated with it.

**Lt Dan** · 03-25-2015, 09:14 AM

Yes, there is a solenoid that connects the house batteries to the chassis battery for boost starting. You should be able to hear an audible click when you press the switch. Even if you hear the click, the solenoid contacts can be burned or corroded to the point they won't make contact, mine were. The solenoid is a large metal "can" with battery leads attached and should be located somewhere near your batteries. It may look like the below photo, lower right center. The Trik-L-Start was added to charge the chassis battery when on shore power.

If there is no sound from the solenoid when the switch is pressed, check for 12v power on the small actuator connector while pressing the switch. The solenoid should have two large connectors for the battery leads and one or two small connectors for the switch power. Some solenoids ground through the case and will have only one small connector. Others have two small connectors, one for power the second for ground.

Cobra1 · 03-25-2015, 09:17 AM

I had to have my wife push the switch on and off while I touched the solenoid. I could then feel the operation. A multimeter can be used to check voltage on the two little wise that are on the side of the solenoid to determine if it is being commanded to turn on.

Waiter21 · 03-25-2015, 11:14 AM

On mine, the Isolator solenoid is powered by the chassis battery. If the chassis battery is real low (dead) the solenoid will not pull in.

I added another relay that I use for charging the chassis battery from the coach, its powered from the coach side.

TexasBounder · 03-25-2015, 11:48 AM

Thanks for all the input. I found a blown 3 amp fuse labeled Aux battery switch. I replaced the fuse. It did not blow but the switch still does not work. No sound or feel of the solenoid pulling in. The solenoid on the 04 Bounder/workhorse is in the fuse bx / battery terminal box drivers side engine compartment. The solenoid looks like an old ford starter solenoid the sat on the fender well. ( easy to hot wire) ha .I think I am on the right path now.More than likely a stuck soleniod, that would explain the blown fuse. thanks again for the help. I will keep ya posted.

Scarab0088 · 03-25-2015, 11:56 AM

Just one add'l comment. The Aux Start switch/system can sometimes be working, but still not allow the engine to crank - IF - the chassis battery is too dead.

This is because a very dead chassis battery can be like an "empty hole" for juice and only a direct jump-start can overcome the dead battery (personal experience).

Of course if this is the case, a battery replacement is needed in short order. Running the engine on alternator power only works but is not great for the system.

Best luck

mel s · 03-25-2015, 12:04 PM

Quote:

Originally Posted by TexasBounder

My Aux battery switch that let's the coach batteries fill in for the dead chassis battery is not working. Can anyone tell me your experience with this and what things I should check first. Is there a solenoid that switches the batteries? Any help to steer me in the right direction would be appreciated
2004 Bounder w / workhorse chassis
Thanks, Bill

Bill
On some, (most?), coaches the Aux battery switch uses chassis battery voltage to activate the "boost solenoid".
If Your chassis battery is "flat" the boost will not/can not work.
Mel
'96 Safari

Waiter21 · 03-25-2015, 12:36 PM

Bill, That solenoid looks like an old Ford starter solenoid, but it is not.

This is an isolator solenoid, the coil is designed to stay energized for long periods of time (days, months).

On the starter solenoid the coil is designed to pull in hard and only be energized for a short period (seconds)

ALSO - Sounds like you already know this, but for the benefit of others, When the coil is first energized, it will draw a lot of current until the armature pulls in. If the armature doesn't pull in, maybe its jammed or dirty and hanging up, or the voltage is just to low and it cant pull in, the coil will draw a lot more current and possibly blow the fuse.

Replace the fuse, If it blows again, and you can determine that the coach and chassis batteries are ok, you might want to replace the isolator solenoid as it may be jamming up.

mel s · 03-25-2015, 04:02 PM

Quote:

Originally Posted by Waiter21

Bill, That solenoid looks like an old Ford starter solenoid, but it is not.

This is an isolator solenoid, the coil is designed to stay energized for long periods of time (days, months).

On the starter solenoid the coil is designed to pull in hard and only be energized for a short period (seconds)

ALSO - Sounds like you already know this, but for the benefit of others, When the coil is first energized, it will draw a lot of current until the armature pulls in. If the armature doesn't pull in, maybe its jammed or dirty and hanging up, or the voltage is just to low and it cant pull in, the coil will draw a lot more current and possibly blow the fuse.

Replace the fuse, If it blows again, and you can determine that the coach and chassis batteries are ok, you might want to replace the isolator solenoid as it may be jamming up.

Waiter21
Correct

That would be a "contentious duty" solenoid...usually in stock at any auto part, (or RV parts) store:

Del City - Search Results: continuous duty solenoid

Mel
'98 Safari

TexasBounder · 03-25-2015, 04:38 PM

The chassis battery checked out at 9.8 VDC . would that be enough to pull in the armature ? This is a new chassis battery and I should mention that the coach was plugged into a 20 amp 120 power source when this happened. The coach batteries showed to be fully charged when I tried the Aux battery Switch.

mel s · 03-25-2015, 05:09 PM

Quote:

Originally Posted by TexasBounder

The chassis battery checked out at 9.8 VDC . would that be enough to pull in the armature ? This is a new chassis battery and I should mention that the coach was plugged into a 20 amp 120 power source when this happened. The coach batteries showed to be fully charged when I tried the Aux battery Switch.

If your Aux switch uses chassis battery voltage to trigger the solenoid only 9.8 volts may not be enough.
Mel
'96 Safari

nothermark · 03-25-2015, 05:27 PM

I get the problem. In my case I would be tempted to pull out my jumper cables and use one to jumper the relay. That is big terminal to big terminal. That big a voltage difference will result in high current and probably sparks.

A better answer would be to connect something like an old fashioned headlight bulb across the relay to limit current flow and let the low battery charge over time. Check the voltage after a half hour. Once you get it up to around 12 it will probably have enough power to pull in the relay. Once that happens it will be held in by the power coming from the other batteries as long as the button is down.

Best case would be to plug a regular battery charger into the AC in the coach and use it to charge the battery. ;-)

TexasBounder · 03-25-2015, 06:20 PM

I may be missing something here. If the Aux battery switch is used to let the coach batteries start the coach in case of a dead chassis battery. what good is the switch if it requires a fully charged chassis battery??