Auxiliary Start Solenoid Replacement

This is relay is the style of many relays used.
The metal case dissipates heat.

Load test both battery banks and make sure they are OK as you could have a shorted cell.

A bad wire connection (ie including lug to wire) can overheat.

Measure the voltage across the terminals, it should be just a few tenths. If OK measure wire to wire. Beg, borrow or steal a DC clamp on ammeter and measure the amps, if both batteries are charged or not charged it should be much less than 100A.

Actually buy a clamp on ammeter, just be sure it will measure DC and AC.

Of course the new relay could be bad...:(

The relay may get warm but should not get hot!
Is this the same style of relay that was removed?

The solenoid coil is an electromagnet and the heat generated is a byproduct of the magnetic field creation process which is normal when in use.

If you have a BIRD and are plugged in then it is doing its job by keeping both the chassis battery and the house batteries charged.

That is the same solenoid I I use in my 2006 Tioga and it has worked fine.

The only time I tested my AUX switch to see if it worked was to place a dead chassis battery then try it to start it,just unhooking it I got nothing.

The solenoid I am using is a White Rodgers 120-105851
I tried to upload a picture but was unsuccessful.
Thank you for your comments.

Endlesssummer wrote:
A while back I needed to use the auxiliary start switch under the dash. The chassis battery was failing. I looked at the old solenoid in the battery compartment and it was hot to touch.
So I replaced it. The new solenoid also is HOT to touch.
Is this normal ?
Also, how can I test to see if this switch is working and will start the MH using the house batteries.
Thank you
Endlesssummer
2006 Fleetwood Jamboree 31M

You’re saying it’s hot to touch all the time? That makes no sense unless it’s maybe partially shorted to ground. Or the trigger wire is sending powder from the switch when it shouldn’t be.
How to test? Disconnect the start battery, push the button, see if the Moho starts. Or see if it starts without pushing the button which means the trigger is getting power when it shouldn’t.

It’s an older Moho, what’s the chance someone had their own Busch light inspired engineering session with the electrical system?

A new relay contacts should be good. If it cools down it is excessive load through contacts. If relay coil is energized and it still gets hot, the coil is issue and good chance it is still not continuous duty. Make and model of replacement relay?
You can energize aux relay by operating switch and it should have a pronounced loud click.
It should also have same click when chassis battery is charged, and battery control center energizes relay to charge coach battery(ies).

Hi
I confirmed that it is a continuous duty solenoid. I will unplug the the electrical cable going to the house and see if it cools down.
How can I test to see if this auxiliary switch will work when needed.
Thanks

Good chance it is the wrong relay. It should be a continuous duty type as it serves as the charge relay.
Excessive charging can cause heating.