Battery Disconnect Solenoid Fuse

[jdrocci]

2005 Holiday Rambler Ambassador 40PLQ

Under the driver seat on the outside is a compartment with a box that contains the battery disconnect solenoid. This solenoid has a nominal 5A fuse in the actuator circuit. Several times, I've lost all DC power to the house and found the cause to be this fuse. The last time it happened, I replaced the fuse with a 10A unit. Yesterday, with the MH parked in my driveway on shore power and the AC running, I locked up the unit and went inside my residence for the evening. This morning when I opened the MH for the day, I found all 12VDC circuits dead and the solenoid fuse blown again, This seems to have happened with no known stimulus.

Is this kind of failure well-known and if so, how/why does it happen?

Joe

[CA_Traveler]

I would expect a HR to use a mechanical latching solenoid. The above link draws 0.5A, heats up to 168F (from a poster) and is intended for a battery isolator type application.

However, owners make various modifications.

[enblethen]

That is correct, if electrically held relay will drop out.

[jdrocci]

I'll do a test tomorrow. I think pulling the fuse should have no affect if it's a latching solenoid. If pulling the fuse disables the 12V, then it's electrically held

[enblethen]

I would like to know what relay you have. Some use an electrical held.
This style is Electrically held

[Dusty_R]

But with a latching relay, when latched, even if the control circuit dies, the things controlled by the relay will continue to work.

Unless they are on the same circuit.

[jdrocci]

Thanks for all the insights guys. What's perplexing to me is that the fuse apparently blew during the night when there was no activity in the MH.
I guess it could have happened when I closed up...maybe I accidentally hit the salesman switch on the way out, which MAYBE caused a momentary short. I doubt that though.

It's a weird one. If I get to the bottom of it, I'll update this posting

[enblethen]

Here is link to a common latching relay used as a battery disconnect.

Intellitec latching relay

This style is used in some rigs
Big Boy
My first guess would be bad rocker switch.

[dougrainer]

The solenoid is called a "Latching" solenoid. It is called this because once closed or open, it draws NO POWER. So, the 12 volt 5 amp fuse should only blow when the Solenoid is activated or deactivated. If this is the case, the solenoid is probably bad and has a short in the Latching circuit. Another possible cause would be the wiring from the Disconnect switch has a short feeding the solenoid. Can you determine by trial and error if the fuse will blow if you try to Open and close a few times in a row? DO NOT INSTALL A LARGER THAN 5 AMP FUSE. There is a REASON it is on a 5 amp circuit. Is this fuse on the large Circuit Board, or is the fuse attached to the actual Solenoid. Monaco used both types. Doug

[enblethen]

The battery disconnect solenoid should be the only draw on the five amp fuse.
Power from fuse should go to switch and then return to the coil of the solenoid. I would check the wiring around the switch and solenoid for loose connection and damaged insulation.
Switch is normally a double pole double throw momentary switch.
Solenoid should draw somewhere around one amp so five amp fuse should be plenty.
Verify that previous owner has not connected other load.
Locate which solenoid your rig is equipped. There is some rigs that have an electrically held solenoid and not a latching type.
I am using solenoid , but I like to call they a relay!

[CA_Traveler]

Not common. If you're referring to the salesman switch then they use a latching solenoid (mechanically latched) and draw no power except when you push the button.

[ksg5000]

Might consider replaying the relay - there not that expensive. In my rig there are two solenoid/relays. One is a latching battery disconnect intellitec relay which has two fuses ... the other is std solenoid used to combine/disconnect chassis/coach batteries based on the position of the ignition key.