Battery disconnect or isolation solenoid? HELP!

[Moffittclan]

I think I might have a bad isolation solenoid because my house batteries aren't charging with the engine running...I tested by measuring volts on house batteries with engine off (12.1) and then with engine running (12.1). I pulled this from behind the green circuit board in the fuse center under the driver side, front of coach...but now I'm not sure if it's the battery disconnect or the solenoid...




As you can see in this next picture, there is a button on the board that says to push it and listen for a click to test the aux start (I'm assuming this is talking about the solenoid??) but when I push it, I don't hear anything. I don't see anything else in this compartment that looks like a solenoid...




We are leaving on a long trip in a few days, so I need help quickly! Thanks in advance!

[Gjac]

Moffittclan wrote:

Gjac wrote:
In your picture you can see 2 large nuts and two small nuts, there should be 12+v across the two large nuts if it is working if only 12+v on one lug it is not engaging. Also check the voltage on the small nuts one should have a 12 v input to the solenoid. You can always jumper the 2 large connection to use the MH for your trip until you get a new solenoid.

Is this the right part to replace if my house batteries are NOT charging from the alternator and if I don't hear any click when I push the battery boost button on the dash of the coach?

Every MH is set up differently. So you need to look at your manual if you have one. On mine I have 3 solenoids/relays(I never know what to call them) If yours is not charging that would be the charge solenoid which can look different on each MH. My battery disconnect looks like the one in your picture, the charge solenoid is the hi tower one in Chris's picture. I replaced both of these from Napa. In either case if they are working they should read 12+ v on either side of the of the large nuts( across large nuts is bad wording). If you are getting the alternator voltage on one side and not the other then the contacts are probably corroded and need to be replaced. Mine were mounted on the firewall in the same box as the disconnect solenoid. If you measure the voltage on these nuts with the engine running and post them here it would help to solve your problem.

[Chris_Bryant]

Moffittclan wrote:

Chris Bryant wrote:
The solenoid in the picture is the disconnect solenoid and has little (nothing) to do with charging off the engine.
That bottom picture references a service manual- try to find it.

Now I'm even more confused...everyone else seems to be saying this does connect the two battery banks to charge them while driving (i.e. convo about jumpering the two large lugs, etc.) but you indicate that's not true???

Correct- *if* the only problem you have is not charging with the engine, that battery disconnect solenoid is not the problem- it turns the batteries on and off- it's a latching relay by Intellitec:


Most charge relays are continuous duty solenoids- typical appearance for those is:

Though they can look different than those.

[MEXICOWANDERER]

A simple Sure Power battery combiner switch would solve nonsense like this. I am bringing a 500 amp rated MOSFET switch to use on Quicksilver. With the four pound irradiated copper heat sink and despiking network it should last 75 years or so rated 24/7 at 400 amps.

The "relay" in the image is a 50 ampere unit despite what the lying label says.

[MrWizard]

can you measure the voltage on the two large lugs with engine running ?

do you have access, or trace the wires back

if that is the 'charge control' solenoid (and not working) one side will have alternator voltage and the other side will have house battery voltage

if both sides have the same voltage low 12.1, device might be working and problem is elsewhere
if one side is high aka alternator and one side is low, then that is the jump start / charge control and it is NOT working
so check the voltage across the two small wires, it may not be getting the command turn on power

the BCC (battery control center) are a know problem, that does fail
usually the control board or one of the fuses on the board,

the house battery system disconnect
disconnects the batteries from the RV systems, meaning NO power to the RV lights etc. NOT to be confused with the charge control/jump start relays

[Moffittclan]

Chris Bryant wrote:
The solenoid in the picture is the disconnect solenoid and has little (nothing) to do with charging off the engine.
That bottom picture references a service manual- try to find it.

Now I'm even more confused...everyone else seems to be saying this does connect the two battery banks to charge them while driving (i.e. convo about jumpering the two large lugs, etc.) but you indicate that's not true???

[wolfe10]

Yes, short term, you CAN "jumper" the solenoid.

But, do NOT use a jumper wire. If either end of the jumper were to come off and tough metal, you would have a DEAD SHORT from one of the batteries.

Safe way is to label the wires on one large lug and ADD THEM TO the wires on the other large lug. Return then to their original position when you want them separated again.

[Chris_Bryant]

The solenoid in the picture is the disconnect solenoid and has little (nothing) to do with charging off the engine.
That bottom picture references a service manual- try to find it.

[Moffittclan]

Artum Snowbird wrote:
Before you get anything new in parts, make sure your ground return is good. Connect from the negative on the house battery to the negative on the coach battery with a jumper cable and just make sure that part is OK. A loose negative will prevent anything from charging.

With just the negatives connected, start the engine and then see what the voltage is at the house battery.

They charge on gen and shore...so I think that side of things is good...

[Artum_Snowbird]

Before you get anything new in parts, make sure your ground return is good. Connect from the negative on the house battery to the negative on the coach battery with a jumper cable and just make sure that part is OK. A loose negative will prevent anything from charging.

With just the negatives connected, start the engine and then see what the voltage is at the house battery.

[Sam_Spade]

Gjac wrote:
In your picture you can see 2 large nuts and two small nuts, there should be 12+v across the two large nuts if it is working

Unfortunate wording.
You should see 12V ON both lugs if it is working. (Exactly the same voltage.)
Seeing 12 V ACROSS the two lugs means something quite different.

[Moffittclan]

Also, I've read you can get one from autozone...how do I know the right part number that is compatible?

[Moffittclan]

Gjac wrote:
In your picture you can see 2 large nuts and two small nuts, there should be 12+v across the two large nuts if it is working if only 12+v on one lug it is not engaging. Also check the voltage on the small nuts one should have a 12 v input to the solenoid. You can always jumper the 2 large connection to use the MH for your trip until you get a new solenoid.

Is this the right part to replace if my house batteries are NOT charging from the alternator and if I don't hear any click when I push the battery boost button on the dash of the coach?

[Gjac]

In your picture you can see 2 large nuts and two small nuts, there should be 12+v across the two large nuts if it is working if only 12+v on one lug it is not engaging. Also check the voltage on the small nuts one should have a 12 v input to the solenoid. You can always jumper the 2 large connection to use the MH for your trip until you get a new solenoid.