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Old 07-11-2022, 09:04 PM   #1
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Brand: Thor Motor Coach
Model: Windsport 31s
State: Florida
Posts: 48
THOR #18965
Use/Store Isolation Unit

I have a 2018 Windsport 31s. The other day my chassis battery was dead so I used the emergency start button to use the house batteries to try to start the motor. That didn't work so I had to jump it. Shortly after that, I noticed my Use/Store switch doesn't appear to operate. Prior to this situation, I used to hear a clicking noise when I hit the Use/Store switch but now I don't hear anything and I cannot get my interior lights to come on without the gennie running on hooked up to SP. I checked the the CBs in the battery compartment and the one under the hood, I even tripped and reset all of them but that didn't help. I checked the batteries and they all tested fine. I checked all of the CB on the main panel and the fuses but everything else is fine. I am trying to rule out things before looking at that Use/Store Isolation unit so can anyone think of anything else that might be the problem? The cheapest I have found this part to cost is around $170 which is fine if it fixes the problem but I don't want to replace it and find out there is another issue. Thanks in advance for your assistance.

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Old 07-11-2022, 09:26 PM   #2
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THOR #9178
Use your VOM and check the voltage across the solenoid and input voltages and then you know exactly what you have going on.
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Old 07-11-2022, 09:56 PM   #3
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THOR #18965
Thanks for the suggestion. So the the Use/Store solenoid is usually in the back? I checked that and one side is 13.52 and the other side is 5. I checked the solenoid in house battery compartment and that is 12.68 on both sides. I attached pics of both.
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Old 07-11-2022, 10:16 PM   #4
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Originally Posted by Rey&Reina View Post
Thanks for the suggestion. I just checked both sides and I got 12.68 for each side.
Your inverter can be used to check the house battery voltage under various conditions. That way you don't have to tear up the bed and get on your knees. With shore power on or generator running check the battery voltage at the inverter. It should be above 13.1 volts with the use/store latching relay in use. If the voltage reading is less than 12.8 volts the use/store relay is in the store position. Using the use/store switch in the entry (first rocker switch in the bottom row). hold the switch in the other position for 1 second the release. Back to the hall to look at the inverter voltage. That will tell-you if the relay is moved. Basically if the voltage in the house batteries is 13,0 or above the charger is charging the batteries. If it is below 13.0 volts the charger is not charging the batteries.
The Intellitec battery isolation relay (it is called a battery disconnect relay on Amazon) in my coach is about $55 on Amazon
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Old 07-11-2022, 10:24 PM   #5
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THOR #18965
I had the two solenoids confused, I was thinking the emergency start solenoid was the store/use solenoid. I checked the use/store solenoid, the picture below and I jumped the wires and still nothing. Lights work fine on SP and Gennie but not on batteries. I checked the wires on the of the switch near the door and everything is connected and nice and tight. The use/store solenoid is much cheaper but the fact that crossing the wires didn't work, I don't think it is the solenoid.
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Old 07-11-2022, 11:10 PM   #6
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I encountered a similar situation and wrote a long thread on it.
No DC power, no "clunk" when I clicked the USE/Store switch.
After an hour of thinking thru the electrical process, along with some trial & error...I figured it out.

Bottomline...It was the solenoid. It gets corroded inside due sparking, thus it won't make the connection.

At the time it failed I was on the road, so I completely removed the solenoid & connected the cables directly to each other (+ to +, - to -). Electrical tape around them. Essentially I was over-riding the solenoid, it was like not having a USE/STORE switch as everything now worked as it should.

And everything worked fine until I returned home.

I then ordered a new solenoid from Amazon (abt $35 at the time).
I also dis-assembled the "bad" solenoid, cleaned it up with a grinder wire brush, so now I have a spare.
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Old 07-11-2022, 11:22 PM   #7
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Here's the thread of my experience and fix with photos

https://www.thorforums.com/forums/f8...ues-26728.html
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Old 07-12-2022, 12:03 AM   #8
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Quote:
Originally Posted by Rey&Reina View Post
Thanks for the suggestion. So the the Use/Store solenoid is usually in the back? I checked that and one side is 13.52 and the other side is 5. I checked the solenoid in house battery compartment and that is 12.68 on both sides. I attached pics of both.
The first picture is your BIM..... Battery Isolation Manager. It is designed to do the following:

- When driving it allows the alternator to charge the house batteries when they drop below 12.6V.

- When on shore power or generator power, it allows the Converter / Charger to charge the chassis battery when it drops below 12.6V.

- It ties the house batteries to the chassis batteries when the Emergency Start Switch is depressed to the house batteries can boost the chassis batteries if it is run down when you try to start the coach.

It is worth checking the wiring..... 90% of the time, Thor wires it backwards where the chassis battery cable and the house battery cables are reversed and on the wrong posts. I have posted about this several time as well. When this occurs, there can be charging as issues and well as issues with the 12V systems such as opening / closing the slide.
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Old 07-12-2022, 12:03 AM   #9
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THOR #7035
Quote:
Originally Posted by Rey&Reina View Post
I had the two solenoids confused, I was thinking the emergency start solenoid was the store/use solenoid. I checked the use/store solenoid, the picture below and I jumped the wires and still nothing. Lights work fine on SP and Gennie but not on batteries. I checked the wires on the of the switch near the door and everything is connected and nice and tight. The use/store solenoid is much cheaper but the fact that crossing the wires didn't work, I don't think it is the solenoid.
That is your USE/STORE Latching Relay.
Measure each of the large terminals voltage to ground without the generator running and without being plugged into SP.

If it is OPEN and everything else is correct then one side will read the house battery voltage and the other side will read 0 VDC.
If both sides read o VDC then the 50 amp DC breaker in the battery compartment that feeds the relay is open and needs to be reset.

If the latching relay is closed and everything else is correct then then both sides will read house battery voltage. House battery voltage should be above 12.4 VDC.
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Old 07-12-2022, 12:46 AM   #10
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THOR #18965
I disconnected the SP and I let the coach sit for an hour and tested everything. This is what I got.

I removed one of the red power wires from the solenoid and jumped it to the other. No lights, nothing works.

VOM on the two CBs in battery compartment, both sides of both CBs read around 13.05.

VOM on the wires on the Use/Store solenoid. One side gave me numbers that jumped all around, up down etc. The other side read at around 6

WITH THE SP ON, I ran a jumper wire from the ground to one of the posts on the switch part of the solenoid and a jumper wire from the power wire. I was able to active it the solenoid. I reversed it and I was able to activate the solenoid. I tried to leave it open and disconnect the SP but either way I activated the solenoid, when I disconnected the SP everything went out.

Is this connected directly to my inverter? My inverter has been giving me an error message for some time and I just have not had time to diagnose that.

Thanks again!
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Old 07-12-2022, 02:10 AM   #11
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Quote:
Originally Posted by Rey&Reina View Post
I disconnected the SP and I let the coach sit for an hour and tested everything. This is what I got.

I removed one of the red power wires from the solenoid and jumped it to the other. No lights, nothing works.

VOM on the two CBs in battery compartment, both sides of both CBs read around 13.05.

VOM on the wires on the Use/Store solenoid. One side gave me numbers that jumped all around, up down etc. The other side read at around 6

WITH THE SP ON, I ran a jumper wire from the ground to one of the posts on the switch part of the solenoid and a jumper wire from the power wire. I was able to active it the solenoid. I reversed it and I was able to activate the solenoid. I tried to leave it open and disconnect the SP but either way I activated the solenoid, when I disconnected the SP everything went out.

Is this connected directly to my inverter? My inverter has been giving me an error message for some time and I just have not had time to diagnose that.

Thanks again!
Your inverter is connected directly to the battery through it's own fuse/breaker and has nothing to do with the latching relay.
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Old 07-13-2022, 07:25 PM   #12
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THOR #18965
Thanks for the replies and the great info. Since the solenoid works when I jump it, it would appear the solenoid is fine. My thought is solenoid is not getting the signal from the switch by the door. Is there a stand alone fuse for that switch? If so, do you know where I should look for it?



Thanks again.
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Old 07-13-2022, 08:10 PM   #13
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THOR #6411
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Originally Posted by Rey&Reina View Post
Thanks for the replies and the great info. Since the solenoid works when I jump it, it would appear the solenoid is fine. My thought is solenoid is not getting the signal from the switch by the door. Is there a stand alone fuse for that switch? If so, do you know where I should look for it?
Thanks again.
Yes there is a 5 amp inline fuse. It is there to protect the coil from over current if the switch is held in for more than a few seconds.
In the picture the coil is in the upper right corner of the bed frame, The red fuse holder is just to the left of the coil.Click image for larger version

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Old 07-15-2022, 12:21 AM   #14
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Thanks again.


I checked that one when I was jumping the solenoid and it was fine. I was thinking there would be one up front with the switch.
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Old 07-15-2022, 01:55 AM   #15
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Originally Posted by Rey&Reina View Post
Thanks again.


I checked that one when I was jumping the solenoid and it was fine. I was thinking there would be one up front with the switch.
No, there are two, 5 amp fuses IN the latching relay:
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Old 07-15-2022, 02:24 PM   #16
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THOR #9511
Use/Store Isolation Unit

Thor uses a variety of battery disconnects depending on the features in your coach. If you have a use/store switch and an LED indicator you probably have what 16ACE27 has shown. If you just have a switch then you probably have what Beau388 has. The best thing to do is to get the model of your BD directly off of the installed BD and find the applications notes online.



I have an Intellitec "non fused" BD with a 5 amp inline fuse on the switch supply line and no LED. My neighbor has a similar Thor coach with a "non fused" BD with two inline fuses...one for the switch and one for the LED. It must have been more "cost effective" to do this than install a fused BD. I'm sure Thor makes audibles on the assembly line due to what is in stock.



Do not rely on the Thor provided 12v layout diagrams...mine shows an RV Custom Products BD on paper and I have an Intellitec 100amp BD as installed. Visual verification is the key to success.
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Old 07-15-2022, 03:42 PM   #17
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THOR #18965
My solenoid is the one in this picture. I have one inline fuse on the wire that goes to the switch post on the terminal. That fuse is 15 amps, not 5 amps.



Even though I can jump the solenoid from the battery wire, I may replace it just to rule that out. I hate to waste the 50 bucks but this stupid thing is really annoying me.
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Old 07-15-2022, 04:29 PM   #18
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If that 15 amp is off the coach battery side, it most likely the keep alive power for your radios.
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Old 07-15-2022, 05:42 PM   #19
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I would agree - sounds like the radio fuse.

Looks like you have an Intellitec BD - canít tell if it is fused from the pix. Take the number off the tag and look on their site. If it is fused then the fuses are under two black covers on the top of the BD.
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Old 07-18-2022, 03:01 PM   #20
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Use/Store Isolation Unit

I had the same issue on my 2017 26B Fourwinds. After doing the same troubleshooting you did I found a small in line fuse block/breaker ( I don't recall the proper name) about 1 in square with a tiny reset button. After pressing the button viola, it all came back to life. Mine was located under the dinette seat on the side wall. My charger is also locates in the same compartment. They're inexpensive and I keep a couple in the MH just in case.
This may or may not be your issue.
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