Community Forums

indigoRV · 09-18-2020, 02:33 PM

Looking for electrical schematic along with parts list for the Dometic MasterFlush RV 7640 toilet. The toilet quit working yesterday. No flush cycle. No water coming in the bowel and no macerator pump energizing when pressing down on the flush pedal. I checked the potable water line going to the toilet and there is positive pressure. It appears there is either no power coming in to the electronic operated solenoid water vlv and to the macerator pump. There are no brkrs tripped and the other toilet is working fine. I have a 2020 fleetwood discovery lxe 40 M and realizing to get info on this rig is almost a full time job. Took me a couple of hours just to find the toilet I believe to be the one installed on my rig. Next week I will call Decatur to start a good dialogue on how to get electrical and plumbing schematics for my rig and what is actually installed and the names of the OEM so I can look up more info.

Old-Biscuit · 09-18-2020, 03:50 PM

Parts List
https://marinesan.com/masterflush/ma...bit-breakdown/

Wiring.......Don't find any diagrams

Toilet has black & Red wires (12VDC Ground & 12VDC POS)
Wall indicator has black, red & blue (12VDC Ground, 12VDC POS and tank level sensor) -----tied into toilet DC Power to shutdown DC if tank is full

Very limited/detail info for that toilet
https://www.manualslib.com/manual/15...40.html#manual

indigoRV · 09-19-2020, 11:47 PM

Thx for the info. I did find the parts list but electrical is hard to come by. What powers the macerator pump, 115 vac, or the same 12 vdc? So if the water is not working, I can always put water in the bowl, but what about the macerator pump? I do not have any indications of black water tank full on my monitors. I do have another toilet that is working, so I do not think it is the tank full safety feature. I wish I knew if I had that feature. There is so much to learn on this rig. I feel like a CHENG again on a ship.

ecsproull · 09-21-2020, 06:46 PM

Quote:

Originally Posted by indigoRV

Thx for the info. I did find the parts list but electrical is hard to come by. What powers the macerator pump, 115 vac, or the same 12 vdc? So if the water is not working, I can always put water in the bowl, but what about the macerator pump? I do not have any indications of black water tank full on my monitors. I do have another toilet that is working, so I do not think it is the tank full safety feature. I wish I knew if I had that feature. There is so much to learn on this rig. I feel like a CHENG again on a ship.

I found the wiring, at least the power to toilet, is coming from you G6A panel. On my coach is is breaker B1 and B9 for the two toilets. If your coach is different it will be labeled under the Breaker section on the G6A panel. I assume you checked these when you said you didn't have any breakers tripped. Since it is coming from this source we are pretty safe assuming that it is 12v.

Before doing anything I would reset the power to the panel by turning off the two main power switches by the door and then turn them back on. Sometimes all you need is a good old fashion reboot.

If this doesn't resolve anything, the next thing I would try is removing the cover of the toilet and see if any of the wires are visible there. If so get a volt meter and see if you have power. If you do have power then there is something wrong with the toilet. If you do not have power there and no breakers are tripped then the problem is between the G6A panel and the toilet. In that case I'd pull the screws out of the G6A panel and check for a loose connection on the back of the breaker.

While you are in the connections to the toilet see if you can disconnect the tank sensor line. There is a possibility that it is giving you a false tank full signal. Since one toilet is still working this seems like a long shot but what do you have to lose by checking.

If all else fails, I would jumper a 12 volt wire to the toilet and see if it flushes.

I hope I haven't confused you too much.

ecsproull · 09-21-2020, 06:52 PM

For this: so I do not think it is the tank full safety feature. I wish I knew if I had that feature.

Yes you do have that feature! There are three sensors on your black tank. 1/3 full, 2/3 full and shut off the toilet full. To see this in action, if you are so inclined, you can pull the panel above the outside shower in the wet bay and see the sensors from there. Get a piece of metal and hold it behind top sensor. This is a very sensitive proximity switch and it will trigger the toilet shut off. And yes there are some days I have too much time on my hands.

ecsproull · 09-22-2020, 08:39 AM

Here is the wiring diagram for the toilet.

If anyone with a 2019 or later Fleetwood Discovery is interested we have a group of about 25+ owners. Send me a message if you care to join us.

indigoRV · 09-23-2020, 02:37 AM

Thank you very much for the diagram. I will start t/s tomorrow morning.

alank · 11-19-2020, 03:37 AM

Did you look in your bag of operators manuals? Should be everything in there you’re looking for.

Macadoos · 05-16-2021, 07:55 PM

Ecsproull, we have a 2021 Fleetwood Bounder 35k and the power is out to both toilets. There was an issue with a sensor and it thought the tank was full and I believe it shut down. I’m looking for where the breaker could be. I’ve seen pics of what it looks like possibly but not finding its location. Do you or any Fleetwood 2019-2020 Bounder owner know where it might be? Looked through manuals and online documentation and nothing. We are in Gold Canyon AZ for the week and no toilets are no bueno.

KeithA320 · 02-27-2023, 06:49 AM

Good Morning (Feb 27, 2023)....
I have a 2020 33D with the Dometic 7640 Model Masterflush Toilet. Since I have had this unit my toilet keeps shutting down when I hit 3/4 tank full indication on the black tank. I had the unit in Decatur and of course they said they fixed it. (Not). Appears there is a wire that is located in the #7 position on the wiring diagram (Yellow Wire). Does anyone know where I can access the Black Tank Level sensors in addition to where the #7 wire attach point is (CB Panel, Back of Toilet etc)? Any help would be greatly appreciated.

Greg_Travels · 04-30-2023, 02:55 PM

Keith I hope you got an answer to your question. I was searching around when I found this thread. I had the same problem with both of the MasterFlush 7640 toilets in my RV. I knew the black tank wasn't full but there is a separate float valve that will shut off the toilets when it thinks its full. So, I had to cut the Yellow wire behind each toilet (cut it in the middle so you can splice it back together some day) and both of them are working fine now.