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Old 05-11-2017, 04:09 PM   #1
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Help: SMB OE Shurflo wiring?

When I got my SMB about five years ago I removed the sink and cabinet and disconnect the power from my Shurflo pump and related switch. I'm trying to get it back working (with a shower setup), but can't quite figure out the wiring as installed by SMB. See the attached photo. The original switch was on the sink cabinet right next to the dinette bench where the pump and tank are located.

There are two heavy, red, SMB standard-issue wires. One tests hot, one has no power. Both have push-on connectors. I'm thinking these went to the switch. There is a smaller-gauge, red wire with an inline fuse. It has no power (tested both before and after the inline fuse), but has a connector like it goes to the pump. There is another similar length wire with no power (white, with wire loom). All four of these wires go back behind the wall paneling.

On the pump there is a red wire with connector similar to the fused wire noted above, and a ground wire with just bare wire (I'm guessing this was ground through the pump's mounting screw). I believe this attached red wire goes to one of the connectors on the pump, although it's currently not plugged in there.

If anyone can help me make sense of this, I'd appreciate it. My guess is the two larger-gauge red wires go to the switch, and the non-powered one gets energized when the switch is connected, and then this wire is connected behind the wall to the fused smaller red wire, which then goes to the pump. I could easily test this theory by connecting the two larger red wires and seeing if the fused small red wire gets hot, but I'm hesitant to do that in case that's not how it's wired.

What am I missing? Thanks!
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pump_wires.jpg   pump_wires2.jpg  
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Old 05-11-2017, 04:54 PM   #2
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Brian, a water pump in any RV is a simple constant hot switched wire, meaning you don't need the key on to use the water pump. You should just have a hot and a ground to hook to the pump at that location, and it appears you do and the third (fused) wire is what may be confusing you.
At your SMB fuse block the hot circuit to the pump should be marked, but if not just run a new one. Give it a 5 amp fuse. You can run the switch through the ground or hot wire.

If you're using a multimeter your testing might go easier if you just use a test light. It's quick and simple to find power and ground wires with a test light, simply clipping/probing one end on a powered wire and the other to any exposed chassis metal close by. I usually use a bolt or screw that I know goes into metal. This should help you narrow it down.
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Old 05-11-2017, 05:17 PM   #3
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Quote:
Originally Posted by 86Scotty View Post
Brian, a water pump in any RV is a simple constant hot switched wire, meaning you don't need the key on to use the water pump. You should just have a hot and a ground to hook to the pump at that location, and it appears you do and the third (fused) wire is what may be confusing you.
At your SMB fuse block the hot circuit to the pump should be marked, but if not just run a new one. Give it a 5 amp fuse. You can run the switch through the ground or hot wire.

If you're using a multimeter your testing might go easier if you just use a test light. It's quick and simple to find power and ground wires with a test light, simply clipping/probing one end on a powered wire and the other to any exposed chassis metal close by. I usually use a bolt or screw that I know goes into metal. This should help you narrow it down.
Thanks Eric. But I know all these wires originally all went to or were associated with the water pump and/or switch. I just don't know which ones go where. (Bad on me for not making note of this when I first got the van and took this apart...) I did test all wires using a test light with ground wire. I know the heavy gauge is hot all the time, and is (likely) tied into the general SMB-installed passenger-side wiring

The 12v SMB schematic I have clearly shows the water pump wiring t'ing off the general passenger side circuit, and having it's own inline fuse (i.e., not on the fuse block itself), which I presume is the fused wire I'm seeing. But it's not hot.

The key question is how to get the fused red wire hot, because that obviously goes to the pump. Maybe I'll just be brave and connect the two heavy red wires and see if it energizes the smaller, fused red wire. I mean, what's the worst that could happen, right?
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Old 05-11-2017, 10:14 PM   #4
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You're right, worst case you'll just pop a fuse. Are you sure you don't have a fuse missing or blown at the SMB (house) fuse panel, or perhaps you pulled the wire (maybe ring terminal) off the circuit there? If that's the case there should be one pretty obviously unhooked but I completely understand what you did. I've done the same thinking I would never go back and then, well, gone back with great frustration about what I UNdid and forgot how.

OK, before I hit send I went back and carefully read and looked at pics. I think you're reasoning is sound. I'm thinking back to how my SMB was, unmolested from SMB, when I got it. Those two red wires must be to the switch. I think the white is your ground, not grounded through the mounting screw but through a main ground block probably right beside your fuse block. I'm almost positive my grounds were white and there were 2 grounding blocks for all white wires right by my fuse block. Also, I'm pretty sure my pump was fused inline like yours looks and not on the fuse block. So, yes, I think you're at the brink of solving this one.
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Old 05-12-2017, 09:11 AM   #5
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So, tested the wires this morning and it's as I guessed: Thick red wires are to the switch, and energize the fused (smaller) red wire when connected. White wire is ground for the pump.

Now just to plumb-in a hose and shower head to the old fitting from the sink and we should be ready to get some water flowing!
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Old 05-12-2017, 10:38 AM   #6
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