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Old 02-27-2021, 02:58 PM   #1
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Water pump is always being fed 12v from hot wire and ground wire is always fed 5v

So I have 1996 Rexhall Rexair

With 3 switch water pump.

Controlled by MPX 7amp latching controller

There is a 12v side and a load side on the controller

12v constant on the red wire
And 5v contestant on pink wire

Now everything works perfectly but I come across the indication light at the check station stays dimly lit. It always has since I've owned the rig.

Wondering if there is a faulty ground or something.

But there is constantly 12v going to the water pump and figured that is odd with no ground... But still works perfectly when switches are flipped.
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Old 02-27-2021, 03:06 PM   #2
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Why does this have 12v going to it's ground?
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Old 02-27-2021, 03:09 PM   #3
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Latching controller.....switches provide the ground path



Latching controller 'bleeding' thru
Replace....1996 you got your monies worth

Don't think you can find a NEW 7a....some USED ones
New is Intellitec 0000145100 10 Amp (about $32-$38...shop around)
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Old 02-27-2021, 03:09 PM   #4
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Light indicator for pump while off and on
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Old 02-27-2021, 03:11 PM   #5
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Why does this have 12v going to it's ground?
For Light circuit on the switch
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Old 02-27-2021, 03:13 PM   #6
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Interesting "bleeding through" how does that work I wonder. Mostly trying to learn how all these switches. Stuff I never learned about in my auto tech classes. Everything else about 12v and how it works on vehicles but these switches are wild how they are engineered.
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Old 02-27-2021, 03:14 PM   #7
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Light circuit? Like for the indicator light. Or ?
Why would the pump have 5v showing up on the ground but still work perfect
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Old 02-27-2021, 06:52 PM   #8
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I don't have the explanation for it but I have noted in testing of certain 12 volt circuits. I recall seeing more than once in service information about how the ground side of a component should show no more than 3 volts positive (or something) when the component is turned off. The instant the component is turned on then that positive voltage disappears and the line goes to full ground. Never made a lot of sense to me but seeing such is certainly not at all unusual.
What you have may be what they call "floating voltage" but I'm not the expert here. I'm sure there's someone more electrically qualified than I around here somewhere to explain.
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Old 02-27-2021, 10:29 PM   #9
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Good to know. First one I have tested ever from the 3 RVs I've remodeled. But I should know of this being that I am certified 12v tech. Just things they never teach ya and just have to learn from experience.
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Old 02-27-2021, 11:19 PM   #10
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Quote:
Originally Posted by GypsyR View Post
I don't have the explanation for it but I have noted in testing of certain 12 volt circuits. I recall seeing more than once in service information about how the ground side of a component should show no more than 3 volts positive (or something) when the component is turned off. The instant the component is turned on then that positive voltage disappears and the line goes to full ground. Never made a lot of sense to me but seeing such is certainly not at all unusual.
What you have may be what they call "floating voltage" but I'm not the expert here. I'm sure there's someone more electrically qualified than I around here somewhere to explain.



You are on the right track...This is a link that addresses a very similar circuit to which the OP has questions. The residual voltage is a byproduct of a pulse forming network that triggers the SCR.


https://www.learnabout-electronics.o...ristors_61.php


The OP's circuit is typical of early remote switching systems. Later systems have used Single pole, double throw switches that allow better control, similar to home multi-point light control. This is predicated on the OP's supplied diagram being complete. Manufacturer functional diagrams are rarely factually accurate.


The lamps remaining dimly lit is probably a normal condition for the circuit.


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Old 02-28-2021, 09:06 AM   #11
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The circuit referred to with a SCR will work, after a fashion but this one is likely to function more to the liking of most people. Working late last night, and I did not choose the best example. Again, this is just an example of the basic circuit that could be used and is not a part for part pattern example of a working RV component. Substitute a motor load for either of the 1K collector load resistors, and omit the LED diodes.
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Old 02-28-2021, 09:15 AM   #12
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Pump (-) does not go to ground. It goes to green latch control circuit. The latch control circuits reconfigure themselves from "On" to "Off". Pump is connected to ground through the latch controller when "On". It is not connected to ground when "off".

This can be done using relays. It has probably been done in this case using solid state circuits. Latch controller circuit board logic would be needed for a full analysis.

I wish you good luck and happy trails ahead!
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