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Old 03-28-2015, 06:14 PM   #1
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What are Jack-knife switches for?

I have 2007 Tropical that has a slow parasitic draw on the batteries when the motorhome is in storage. The chassis batteries have two jackknife switches and the house has one. I thought pushing the red button and releasing the switch and it would disconnect the batteries form the parasitic draw. That's not the case as everything in the coach still works. Now I'm wondering what these switches are for.

Robby
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Old 03-28-2015, 06:32 PM   #2
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Typically jackknife switches are mounted right on the battery post and they disconnect the battery from the rest of the RV. Look carefully at your batteries and see if the cable goes directly to a knife switch or there other, smaller gauge wires bypassing the switches. Those switches were not factory installed, a previous owner installed them, for what ever reason.
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Old 03-29-2015, 04:16 AM   #3
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Quote:
Originally Posted by BFlinn181 View Post
Typically jackknife switches are mounted right on the battery post and they disconnect the battery from the rest of the RV. Look carefully at your batteries and see if the cable goes directly to a knife switch or there other, smaller gauge wires bypassing the switches. Those switches were not factory installed, a previous owner installed them, for what ever reason.
I'll give it another look Bob. They are large gage wires coming of the positive side of the batteries. I think I'll try a volt meter to see if the switches even work.

Thanks,
Robby
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Old 03-29-2015, 09:20 AM   #4
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The switches were probably installed to eliminate most of the parasitic load on the batteries when in storage. I'd open them if I was planning on more than a week or so between uses.

Internal losses will run down a battery over long term storage. The different battery types have different losses and different storage times but it is worth charging all of them periodically.
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Old 03-29-2015, 09:32 AM   #5
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The switches were probably installed to eliminate most of the parasitic load on the batteries when in storage. I'd open them if I was planning on more than a week or so between uses.

Internal losses will run down a battery over long term storage. The different battery types have different losses and different storage times but it is worth charging all of them periodically.
But the OP said with the switches open, "...everything in the coach still works." I'd think the switches must have been for something else. I've not seen a true knife switch that can malfunction and still conduct electricity except when the blades reconnect with the other side of the switch. I'm puzzled by the OP's mentioning, "... pushing the red button and releasing the switch " I've not seen knife switches with red buttons, but these switches are obviously not set up to cut off all battery power to the RV for storage purposes. I have such switches mounted right on my house battery terminals and have left the RV in storage for as long as 4 months with no charging current and still been able to start everything back after an Ohio winter.
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Old 03-29-2015, 11:05 AM   #6
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Is it possible that the relay for the switch failed and the previous owner installed the knife switches as an alternative? If you open the knife switches, the coach powere should be off.
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Old 03-29-2015, 11:13 AM   #7
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I think the OP is calling the lever type, thermal circuit breakers, jack knife switches.

They have a red button to disconnect them.

All three, could be feed wires to the BIRD.

Could be wrong.
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Old 03-29-2015, 11:20 AM   #8
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not a jack knife switch
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Old 03-29-2015, 01:59 PM   #9
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This is about as simple a knife switch as I can find, some have double throw, or double poles, or even double pole double throw, but it's evident when the switch is open or closed.

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Old 03-29-2015, 02:07 PM   #10
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But no RED button!
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Old 03-29-2015, 02:10 PM   #11
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But no RED button!
I agree, but hard to confuse the thermal CB for a knife switch!
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Old 03-30-2015, 04:54 AM   #12
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I agree, but hard to confuse the thermal CB for a knife switch!
Well Bob, it my case it's not that hard to do. It is as pictured with the red button, it think your calling it a thermal CB. With those switches open everything still works. To be clear I haven't tried everything but all the lights, fans, radio and stairs work. What would be the function of these switches?

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PS, I haven't figured out how to post pictures yet.
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Old 03-30-2015, 05:56 AM   #13
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I have 3 of them breakers on my class C.

#1 protects the cable used for the boost circuit. It is near the house battery.

#2 protects the chassis to house, charging cable. It is near the engine battery.

#3 protects the cable from the house battery, to the fuse and converter feed. That one should cut the power to the house loads, but I never tried it.
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Old 03-30-2015, 06:09 AM   #14
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But the OP said with the switches open, "...everything in the coach still works." I'd think the switches must have been for something else. I've not seen a true knife switch that can malfunction and still conduct electricity except when the blades reconnect with the other side of the switch. I'm puzzled by the OP's mentioning, "... pushing the red button and releasing the switch " I've not seen knife switches with red buttons, but these switches are obviously not set up to cut off all battery power to the RV for storage purposes. I have such switches mounted right on my house battery terminals and have left the RV in storage for as long as 4 months with no charging current and still been able to start everything back after an Ohio winter.
Yes. One of the things I learned a long time ago was not to totally trust what the user reported. In this case of the converter was plugged in everything would work. The OP did not say. The real question seems to be what is connected to the switches. I took the red button to be the salesman switch. What we really need is to know what's connected to the switches.
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