No house DC after using aux start

[Air2Mud]

This situation has REALLY stumped me: I had to resort to using the Aux Start capability on my '16 Jayco 29MV to help a weak chassis battery. Despite a few attempts it turns out the chassis battery was so far dead the push from the house battery was no help. So a new chassis battery was installed. (the floating voltage level on the house battery afterward measured ~13.2V)
Fast forward after the new chassis battery install: The engine starts easily and everything connected to the chassis battery is happy. But there's no power to ANYTHING back in the house and the 12-V Battery Disconnect switch is non functional. The fuses located on the disconnect switch solenoid/relay in the battery storage compartment are intact/nothing blown and all the fuses in the master panel (inconveniently located at the foot of the bed) are intact as well.
So, without any sort of a wiring diagram to aid in troubleshooting... does anyone have experience with this problem or could guide me in a direction to start isolating the problem?

[katiedog]

I have had a similar issue,
After checking fuses at Battery compartment I tested that solenoid
which seemed ok. but hard to check without Power
Next was solenoid under hood for Aux battery boost.
It had failed due to high amperage caused by loose wires and loose ground.
Easy $12.00 fix.

[cabinetmaker]

Sure sounds like your house battery died also. I would replace or charge it then check everything again. Will your generator start? If so it might charge the house battery enough.

[Air2Mud]

As mentioned, the house battery is OK as it has retained its charge despite the less than successful boost attempt to the chassis battery.

[Air2Mud]

Thank you! I will see if I can locate and evaluate something under the hood that resembles the description of what you describe. [;\}

[katiedog]

Try Pushing AUX start button with hood open . It clicks pretty loudly,
It should have 2 small wires and 2 very large battery size wires.
On our 31DS it is mounted on upper edge of firewall on drivers side.
After 40 years of RVing I always carry a spare solenoid.
Jayco uses 2 or 3 in their RVs

[Air2Mud]

The marked photo shows what I found and measured. My sense is that there is something amiss between the house battery and the power relay under the hood: 12V chassis power is picked off the bottom side of the relay and sent somewhere else, presumably to be selectively sent back to the coil in order to connect the + sides of the chassis and house batteries.
The two solenoid coil terminals are electrically connected to either side of the coil - one side to chassis ground. When 12V is put on the "high side of the coil it will energize the relay and connect the two large terminals, thus electrically connecting the batteries. But there is no 12V coming from the house end of things to connect to the + side of the chassis battery.
None of this answers the question about the working order of the house battery relay and solenoid. All I know is that the fuses associated with that component are OK; beyond that I don't know. That will be step #2 for another day.

[katiedog]

There is another relay in Battery compartment that could be bad.
I have jumped around the relay at the large battery cables that are hooked to it.
Keep looking , you will find the answer.

[Air2Mud]

Yep, that's the plan. LOL, thinking back, that is the first thing I should've tried. Gah. Thanks for the encouragement!

[in the wind]

Shouldn't be getting any voltage across the red fuse block.

[Air2Mud]

Originally Posted by in the wind

Shouldn't be getting any voltage across the red fuse block.

Uhhhh, the voltage to the fuse block comes directly from the chassis battery positive terminal... Look at the terminal source label.

[in the wind]

No, If you measure across a fuse, any fuse, with a DVM, with power applied, one lead on one side the other lead on the other side, there should be no voltage.

Its called a difference in potential. If the fuse is good, there will be no voltage reading. Its like measuring a solid wire with voltage applied, you wont get a voltage drop any where along the wire.
In your case, you have a voltage drop across the fuse.


Do you have continuity across the fuse, measured with an OHM meter??
Should measure zero OHMS.

[Air2Mud]

You are absolutely correct, I now understand the basis of your insistence of being 100% correct.
I mislabeled the photo in that the voltage was measured on either side of the fuse block with respect to chassis ground, not "across" the fuse block. My bad, my mistake; I humbly apologize and beg for forgiveness.
Today Jayco graciously emailed me a complete set of year/model VIN specific electrical and audio/video drawings. I am very thankful for that.

[in the wind]

No worries..

[Cunning193]

Anyone know the source for the positive connection on the small terminal of the solenoid?

[RyRoRyan]

There are two solenoids in your rig. One for the aux jumper and one for the main disconnect to the house. It sounds like your main may have an issue. There is a thread here..

https://www.jaycoowners.com/forums/f...oid-25661.html

Which explains how to reset the relay. Also note there is a fuse on that relay. Make sure that is good. The one you are looking for is the one that does NOT have a chassis lead going to it.