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Prairie · 07-10-2018, 09:44 AM

I was ready to pump out my holding tanks at a campground last week when I discovered the macerator pump fuse was blown. I replaced the fuse and everything worked okay I pumped out and stowed the hoses and proceeded on my trip with the pump switch turned off and the valves closed. When I prepared to pump out yesterday, I discovered again that the fuse was blown. I replaced the fuse and everything worked okay. It seems that the fuse blows when the system is not powered and in use. When I pump out I switch the pump on and off several times when changing from Blackwater to Gray. Any ideas or experience with this type of problem would be greatly appreciated. I'm afraid that I can't just keep replacing fuses every time I pump out. Something is not right and I need to fix it. In the meantime I remove the fuse after I pump out.

rmkrum · 07-10-2018, 10:24 AM

Try tracing and inspecting closely the wiring from the fuse to the switch then to the pump. It's entirely possible the wire is chafed and grounding out somewhere between the fuse and the switch when you are on the road.

Vibration can chew through wire insulation near an unprotected metal edge, and I bet that's what is happening. Admittedly it may be a total pain in the tail to inspect every inch of the wire...but that's what it takes to find intermittent issues like this.

gmillerok1 · 07-10-2018, 10:39 AM

More than likely, if it doesn't blow when you use it but does when you later try, it shorted out as the previous poster suggested.

It could be that the connection at the switch is faulty, so if it were me, I'd inspect that first since it's easy to do (just remove the screws from the panel and pull it out).

Since the motor is only energized after the switch is turned on, and since it only blows later, it has to be somewhere between the switch an fuse. While it could be something as difficult to find as an errant sharp screw poking through the positive wire in some random location, the first step is to eliminate where connections are made. It could be something as simple as a poor connection behind the switch. Then I'd examine carefully the wire to the DC panel and make sure that looks ok. Then, trace the wire back and see if you can figure out where the short is occurring on the positive wire.

Prairie · 07-10-2018, 11:28 AM

Thanks r m k r u m & GMillerok. Your answers or what I suspected would be the problem but it's always good to have confirmation. Looks like I'll have to start inspecting the wiring and connections and hopefully can find a short.

OTRA15 · 07-10-2018, 11:33 AM

Great advice . . . good luck searching!

Peter

PS -- Any chance that there is an intermittent short in/near the pump motor, as it cools down, after running and getting hot? I would check especially the wiring connections right at the motor. That is the area that might have the most thermal expansion and contraction, not to mention vibration IMO.

gmillerok1 · 07-10-2018, 02:16 PM

One more thing. Check the schematic (if you can get one) to see if the fuse covers anything else. I'm not sure how they wired it, but if that's the case, it may not even be related to the motor at all (for instance, if they use electric valves or reel like they do in my 2011 and use the same fuse)

Something to consider.

Prairie · 07-10-2018, 10:23 PM

I have replaced the wire from the fuse to the switch and things have tested out good so far. No fuses blown. I'll be on the road for a few days, we are on an eight week trip to Alaska and back to North Carolina, and will see how things go at the next pump out.
Thanks for all the replies and good suggestions. This forum is great!

amirm · 07-10-2018, 11:34 PM

Mine has blown twice in two years. I keep spares for that reason. I think it is a poor design. It should have a DC breaker, not a fuse. The initial surge depending on how stuck the pump is, causes the fuse to blow.

OTRA15 · 07-11-2018, 03:27 AM

Quote:

Originally Posted by Prairie

I have replaced the wire from the fuse to the switch and things have tested out good so far. No fuses blown. I'll be on the road for a few days, we are on an eight week trip to Alaska and back to North Carolina, and will see how things go at the next pump out.
Thanks for all the replies and good suggestions. This forum is great!

Thanks for the update, good luck!

Peter

wachuko · 07-11-2018, 05:39 AM

That is great news. And thank you for confirming culprit and solution. Safe travels!!!

'55 Airlight · 07-11-2018, 10:11 AM

Quote:

Originally Posted by Prairie

It seems that the fuse blows when the system is not powered and in use.

I have a macerator pump for the blackwater tank in my '55 Airlight. The system has worked great -- except last year it starting blowing fuses when I powered up the macerator pump. The installation of a relay solved the problem.

Macerator pumps are terrific until they fail.

Air99 · 07-11-2018, 10:38 AM

Couple things to add...the pump electrical circuit also powers the rear exterior cigarette 12v outlet, and on your next pre pump try to manually turn the motor/pump tail shaft to check how tight it feels, it could be bound up with hair or debris.

Prairie · 07-12-2018, 10:05 AM

I drove 200 miles yesterday on some pretty rough roads with a new fuse installed in the macerator circuit. The fuse is still good this morning so the macerator pump should work at my next pump out. With any luck, this will be my last installment on this thread.
Prairie out.

rowiebowie · 07-13-2018, 08:21 AM

Great news. This forum is a terrific place to get help, bounce ideas, and sometimes just confirm your course of action. Happy travels!

Alex AVI · 07-15-2018, 01:53 AM

Quote:

Originally Posted by Prairie

I drove 200 miles yesterday on some pretty rough roads with a new fuse installed in the macerator circuit. The fuse is still good this morning so the macerator pump should work at my next pump out. With any luck, this will be my last installment on this thread.
Prairie out.

PRAIRIE - Awesome. That one motor we want working always

Bobber79 · 07-20-2018, 11:09 AM

Wow, this just happened to me last week. I replaced the fused and it worked fine. I guess I'll find out if it keeps happening.

gmillerok1 · 07-20-2018, 01:16 PM

Generally, the fuse will blow if the motor stalls, usually on startup because of debris or other crud keeping it from turning.

Be sure to always use a filter in the drain if you use the shower, avoid those dissolving packet tank chemicals (they don't completely dissolve and can cause issues with the pump), or putting other things down the drain that can clog it up. After an extended use, you may want to use a screw driver on the motor be sure it can turn freely before going on a trip.

That way, you may avoid fuse blowing.

Bobber79 · 07-21-2018, 06:28 AM

Thanks! Where exactly is the pump located and how do you get to it to check it out? I’d guess underneath, close to the hose reel?

gmillerok1 · 07-21-2018, 08:22 AM

Streetside, just in front of the door where the hose reel is located, sticks out below the van frame on a black L-Bracket. The other side is connected to the waste system. You can't miss it. There is a rubber cap (more like a stopper) on the end of the motor that faces you that you can see. It just pops off and you will see a slot for a flat bladed screwdriver that will turn the motor if you ever need to do so.

While you are checking that out on the ground looking up, inspect the wires to the motor. They tend to be hanging all over the place and just swingin' in the wind. If so you may want to secure them with a zip tie to keep them from being chaffed and shorting out.