Continuing problems with Thetford toilet

When we first used our new Thetford toilet in our 2009 3124KB, it didn't work properly...even one sheet of tp did not flush down. We contacted Thetford, and the local rep, and he replaced the pump, saying the toilet now worked. When we went out again for 10 days, it was obvious that the toilet did not work any better than with the first pump. There is not enough force to the flow of "water" and it comes out only from the back and part of the back left side. Finally today, Chris found someone at Thetford who seemed to have an idea what might be wrong. He said that our symptoms were the same as if the wires to the pump were hooked up backwards. Now here is the question? Do you all think we can change the wiring ourselves? Our local rep is obviously a hack and the nearest place that might repair the problem doesn't do warranty work and charges 140/hour, and we don't have much confidence in them. We have no wiring diagrams and don't even know if we can easily reach the wiring. BTW the good guy at Thetford said the pump would run if the wiring was backwards, just not run properly. Thanks for your help....

[ShrimpBurrito]

Interesting. If the polarity on the pump is reversed, then the pump is just running in reverse. I don't know the water flow design, but if the pump is an impeller design, I suppose it's possible it could still pump water -- but I'm not sure why that would create the problem you describe.

But switching the wires is not difficult. Remove the 2 phillips screws closest to the top cover behind the seat to uncover the wires.

At the most, it would involve cutting, stripping, and wire-nutting 2 wires together. 5 minute job. If you don't have wire strippers, go get a pair (no more than $10) -- you'll need them again for another project. And if the pump has blade fittings, it would take about 10 seconds to change, no extra tools required.

Dave

[Wavery]

Originally Posted by ShrimpBurrito

Interesting. If the polarity on the pump is reversed, then the pump is just running in reverse. I don't know the water flow design, but if the pump is an impeller design, I suppose it's possible it could still pump water -- but I'm not sure why that would create the problem you describe.

But switching the wires is not difficult. Remove the 2 phillips screws closest to the top cover behind the seat to uncover the wires.

At the most, it would involve cutting, stripping, and wire-nutting 2 wires together. 5 minute job. If you don't have wire strippers, go get a pair (no more than $10) -- you'll need them again for another project. And if the pump has blade fittings, it would take about 10 seconds to change, no extra tools required.

Dave

You're right Dave. That makes little sense. If the pump were wired wrong it would "Suck" water from the pressure side and "push" water from the suction side of the pump. It seems to me that would just blow bubbles into the tank.

It sounds to me like the pump or the hose from the pump are not located properly or something is blocking the intake OR there is not enough water in the tank to prime the pump..Nonichris......I hope that you realize that it takes about a gallon of water to prime that toilet.

I wouldn't reverse polarity myself, if it is under warranty. Reversing the direction of the impeller could damage the impeller. Most pump impellers are designed to run in one direction and reversing the direction can stretch and distort the impeller vanes. Some impellers will run in both directions but very poorly. A directional impeller is 100% more powerful than a bidirectional impeller. The pump in my toilet moves a LOT of water.

Wayne

You can check the polarity with a volt meter or test light. The black wire should be positive. A test light should light between the black wire and ground. Take out the fuse and connect to the line side of the fuse not the motor side so you don't read back through the motor. An easy place to find ground is the case of the power converter or the outside ring of the cigarette lighter socket in the TV outlet.
If it is wrong, follow the rubber covered cable. Look behind the panel under the kitchen sink. You will probably find a splice there.

Another possibility (though not as likely) is the leads on top of the motor may have been installed backwards. The motor is removed by carefully pulling up on the rubber boot. Don't loose the plastic shaft coupling. Sometimes it comes out with the motor then falls off. Once you have the motor out you can pull back the boot to get to the connections.

If the mechanic at Thetford had not said what he said, we would not have considered reversing the wiring, but of all the people Chris has talked to, he seemed to know what he was talking about..he did say that water would flow into the toilet and have the symptoms as we described..and he gave Chris his personal number to call back, so we would certainly talk to him again to find out exactly which wires he meant. It is odd, to be sure, and we are teachers, not mechanics, or electricians, so it is way more difficult for us to cope with. We do put enough water in to fully charge the toilet...so that is not the problem...we certainly do not want to do anything that would damage the works.

If the pump was running backward it would suck air in from the bowl top and blow bubbles into the holding tank.
Several Questions, Did it pump water when your dealer did the demo walk through?
Do you have enough water in it? If the initial charge is not well up into the green area ( assuming the gauge is correct) it will not pump the correct amount of water. I would add another gallon or two before I switched the wiring,

[ShrimpBurrito]

Originally Posted by rumbleweed

If the pump was running backward it would suck air in from the bowl top and blow bubbles into the holding tank.

I don't think this is true if the pump is an impeller design. The vanes on an impeller are straight blades, and I believe will pump fluid in the same direction, regardless of which way it's spinning. If I am thinking correctly, the only thing the impeller direction impacts is whether the fluid gets pumped to the right of the shaft or the left of the shaft. Either way, the fluid still gets from tube A to tube B. Sorta like a water pump in an outboard motor.

However, after the pump is run for some time, the vanes will start to sway in one direction -- thus, harveyrv's caution that if the pump is reversed if the vanes are already swayed, it could cause damage -- to the impeller or the motor. But their unit is brand new, and the pump only runs for seconds at a time -- even with their continual messing with it to determine the problem. I doubt the vanes will have swayed yet.

And speaking of impeller vanes, if some of the vanes have broken off (perhaps the impeller was not lubed during manufacturing), that would definitely impact water flow, both by blockage and by reduced pumping power.

Dave

The pump(s) have both pumped water, but only from the back and the left side of the back facing the toilet...it is not of sufficient force or volume or coverage to push one sheet of tp through the opening to the tank. We definitely will try again with more water, but we have done all sorts of things already, including pouring exogenous water through so that the tank fills to capacity, and the pump volume has not changed. Probably during the walk through they simply saw that water flowed and did not check to see if it was of the correct volume and force. The so called Thetford rep said it was fixed and that that was the way it flushes and that is why people don't like them and if we wanted he could replace it with something else....It took over a month to get a new pump and get the guy to come out, but it seems as though he either isn't that good of a repair person or wanted to get more money out of us???? That is why we thought maybe we could do something ourselves...it is quite frustrating...Could we remove the whole toilet and just take that rather than haul the trailer down to someone who might fix it?

We had a similar problem which had nothing to do with the pump. As I understand the fix, the water feed tube (s) has come unattached from under the toilet rim. Maybe some of you who have had the Thetford apart could comment on this...

A turbo pump is like a fan. If you run it backward the fluid flows backward. It is very unlikely that this is a turbo pump. They are too expensive.

Positive displacement pumps are pressure pumps and valves control the direction of flow. Your tire pump is a positive displacement pump. But this is not a high pressure application.

Centrifugal pumps are much cheaper. They are usually low pressure high volume pumps. Correct application. The fluid comes in to the center of the rotating impeller and centrifugal force flings it to the outside of the pump bowl where the discharge is. The impeller vanes are shaped and the discharge is placed in such a way as to cause the maximum amount of fluid to exit out the discharge when it rotates in the correct direction. If it runs backward the water still enters the center and gets flung to the outside but just gets churned up and not much goes out the discharge.

In other words;
If it is a centrifugal pump and it is running backwards. That would explain the symptoms.

Talk to a neighbor or friend who is comfortable around 12V DC power and ask him or her to test the polarity of the wiring.

My bet is that the wires are crossed at the splice under the sink. Or (I’m hedging my bet here) there is a blockage.

Let us know what fixes it