Useful Repair Info...omnivent And Thetford. (1 Viewer)

pappajohn

LIFE MEMBER
Aug 26, 2007
43,323
49,428
Dark side of the moon
Funster No
172
Exp
Since 2005
During our shakedown weekend away i fould the thetford toilet didnt flush (electric flush) and the Onmivent extractor was weak and intermittant.

The toilet is a Thetford 200CWE.
I replaced the fuse which blew the instant the flush button was pressed.

The flush button is on a removable bezel which is held by two plastic 'posts' and some non setting mastic sealer...prise off carefully with a broad blade screwdriver.
underneath the bezel is a plastic grid held with 4 screws...2 x rear..2 x front...ignore the center ones, they hold the plastic posts.
when removed look to the left, you will see the white filter, follow the pipe down and you will find the pump.
CAREFULLY unclip the pump amd hoses, one hose directly below the filter and one at the opposite side to the bowl outlet.
lift out the pump, filter and hoses.

Look underneath the pump, you will see a red wheel with ribs...this is the impellor and chances are it wont turn.
use a small screwdriver to gently turn the impellor, it gets easier as you turn it.
i stood it in a small glass of vinegar for half an hour to break up any limescale...seemed to help.

Once it turns freely replace the blown fuse.
its a 3amp but not having one i fitted a 5amp.
hold a bit of rag over the pump outlet and press the flush button.

If the fuse still blows you either have a duff pump or a wiring fault assuming the impellor is free to spin.
reassemble in reverse order.

The 3 speed reversible Omnivent. (Probably other models apply)

The #1 common fault.....stuck brushes in the motor.

Indoors, remove the 4 screws holding the fly screen and remove screen.
remove motor wires from switch (theres only two and may be a resistor between them, do not seperate) taking note which goes where.
the connectors are hard to get out of the small hole in the plastic motor mounting frame so i cut them and fitted new connectors on reassembly
Hold the fan blades and remove the spindle nut, its threadlocked and tight, undo anticlockwise.
remove the fan but MAKE A NOTE OF SPACER WASHERS !!! Inc the very thin nylon/fibre one.
In my haste I think i got it wrong as on assembly the fan wouldnt turn.
on the roof remove the 2 motor retaining screws and lift out the motor.

using a thin driver seperate the top cover from the motor body, the driver may need a tap with a small hammer etc to start it moving.
its hard to seperate as the permenant magnet tries to hold the cover on.
in the cover are the brushes....one will be stuck in its housing.
dont attempt to remove either as the wires need desoldering first.
i simply worked the stuck brush in and out in its housing until it moved freely.
i also used some fine wet n dry paper to clean the commutator segments which, because of the stuck brush, has burnt slightly.
reassembly is the reverse ensuring the brushes dont get trapped as the lid goes back on.
i used a new nyloc nut on the spindle instead of the plain nut and threadlock.
check the fan spins freely, if not you need to slacken the nut slightly...but only enough to allow the fan to spin....this may be where i got the spacers wrong.

Start the fan on 1, then increase to 2 then 3.

Speed 3 is now hurricane force and the fan whines slightly with the speed.
the volume of air being drawn in or out is amazing compared to the feeble effort before.
 

Riverbankannie

LIFE MEMBER
Mar 11, 2016
10,529
61,521
Bristol
Funster No
41,967
MH
IH 630 RL PVC
Exp
12
Picked up this useful thread, thanks @pappajohn :)
We have the dancing lights on the omnivent.

The motor does not appear to be stuck in any way so thinking problem could be damp on pcb. Various other threads mention sealing the pcb and connectors with silicone.

Would this be silicone spray (like in the Thetford toilet seal spray) or silicone sealant (as in the thick gluey stuff).
It would seem to me to be the first sort, but wanted to check(y)
 
Oct 30, 2010
4,256
20,707
Suffolk or France or ........
Funster No
14,290
MH
A Class Carthago Chic
Exp
Since 2008
Our Omnivent has always been a bu&&er from new.
Sometimes it would run OK, at other times the red LED's would 'dance' and it would cut out.
It's been like that for 3 years so it wasn't used much.
Miraculously it seems to have cured itself lately and it runs well.
I wonder how long it will last?

Richard.

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Riverbankannie

LIFE MEMBER
Mar 11, 2016
10,529
61,521
Bristol
Funster No
41,967
MH
IH 630 RL PVC
Exp
12
Our Omnivent has always been a bu&&er from new.
Sometimes it would run OK, at other times the red LED's would 'dance' and it would cut out.
It's been like that for 3 years so it wasn't used much.
Miraculously it seems to have cured itself lately and it runs well.
I wonder how long it will last?

Richard.
We use ours a lot as it’s over the cooking area so useful to remove steam but often it’s the toast ! The smoke detector is also near the cooker so it’s helpful to draw the smoke away and also when it’s hot, I like the inward fan drought effect. I didn’t think I would use it but found that I do.

One problem is that’s it the most useful vent to have cranked open at night so it’s not closed when raining. I didn’t realise how vulnerable the motor and PCB is.
 
Oct 30, 2010
4,256
20,707
Suffolk or France or ........
Funster No
14,290
MH
A Class Carthago Chic
Exp
Since 2008
One problem is that’s it the most useful vent to have cranked open at night so it’s not closed when raining. I didn’t realise how vulnerable the motor and PCB is.
I think that might be what caused some of our problems too.
You can't see when the vent is open and we have left it once or twice when its rained.

Ours is also above the hob and it tends to be forgotten about until the smoke alarm starts shrieking. :rolleyes:

Richard.
 

Riverbankannie

LIFE MEMBER
Mar 11, 2016
10,529
61,521
Bristol
Funster No
41,967
MH
IH 630 RL PVC
Exp
12
I think that might be what caused some of our problems too.
You can't see when the vent is open and we have left it once or twice when its rained.

Ours is also above the hob and it tends to be forgotten about until the smoke alarm starts shrieking. :rolleyes:

Richard.
Hoping we don’t have to buy a new PCB !

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Riverbankannie

LIFE MEMBER
Mar 11, 2016
10,529
61,521
Bristol
Funster No
41,967
MH
IH 630 RL PVC
Exp
12
It’s not been working since last July and we’ve just got around to looking at it. It’s been quite dry here recently :whistle:
 

DP+JAY

LIFE MEMBER
Mar 17, 2010
2,533
14,782
Dalbeattie
Funster No
10,674
MH
Laika 5009
Exp
since 2007, 25 years tuggin before that.
Picked up this useful thread, thanks @pappajohn :)
We have the dancing lights on the omnivent.

The motor does not appear to be stuck in any way so thinking problem could be damp on pcb. Various other threads mention sealing the pcb and connectors with silicone.

Would this be silicone spray (like in the Thetford toilet seal spray) or silicone sealant (as in the thick gluey stuff).
It would seem to me to be the first sort, but wanted to check(y)

I would think more likely silicone GREASE.

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