cruiser Posted May 29, 2014 Share Posted May 29, 2014 Having become a toilet cassette expert yesterday, (thanks to the Forum).....I now have a new challenge for you. The full- warning light still won't go on. I disconnected the LED and checked it on a 9 volt power supply, it works fine. I then put my multimeter across the feed wires, and taped a magnet to the sensor. The meter showed a gradual rise to about 11-ish volts I then added the LED across the still-connected meter and the voltage dropped to 1.5 or thereabouts, then gradually climbed to 12 volts, but the LED didn't light. Removed the meter and connected the LED, no light. Any ideas? Hopefully, there's a simple solution, as I don't want to get bogged down with this problem. (Sorry, couldn't help myself....cut my teeth on Carry On films) Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 29, 2014 Share Posted May 29, 2014 Based on the fact that your Rimor is 2004-vintage and there's an LED cassette level-indicator I think your Thetford toilet is one of the C-200 'swivel bowl' models, but it might be helpful if you can say exactly which onel. There is a large downloadable set of repair instructions for Thetford toilets but, if yours is a C-200, I don't think these will help as that model's level-indicator isn't (apparently) covered. The usual reason for a level indicator LED not illuminating has to do with the float in the cassette, but it should be possible to test the indicator with a magnet as you've been doing. I note that you've confirmed that the LED illuminates OK when powered by a 9V supply. I presume you have also established that the LED is not polarity-sensitive. As both connecting wires had broken away, reconnecting a polarity-sensitive LED the 'wrong way round' would be significant. (I'm pretty sure the LED is not polarity-sensitive - it's just a clutching-at-straws thought!) Can't really offer a credible remote diagnosis on this. If you are testing the sensor-switch + LED combination in a way that should cause the LED to illuminate and it won't, then I guess it's the switch that's the prime suspect. This link MIGHT help http://www.bradtech.ltd.uk/products/Thetford_Cassette_C200_Toilet_Spares.html Link to comment Share on other sites More sharing options...
Guest Had Enough Posted May 29, 2014 Share Posted May 29, 2014 Please don't think that I'm teaching my granny to suck eggs but I've no idea how long you've been motorhoming. Anyway, my advice is that you shouldn't get too fixated on mending a warning light. I'm assuming that you can see the contents of the cassette when you open the blade? I can see how full it is without worrying about the light coming on and then I act accordingly. My policy is to put in half of the recommended toilet fluid and empty it when it's about half full. If you don't get the chance to empty it slip in a bit more fluid via the blade entrance. It's easier to carry as a full cassette can be quite heavy and if the emptying point is a good walk away it can be a bit of a struggle for some people! Unless of course you have wheels on it, which I don't but even then it's much easier when half full. If you leave it until the warning light comes on and then there isn't a nearby emptying point you may well be in danger of overfilling it, which isn't pleasant. Link to comment Share on other sites More sharing options...
Billggski Posted May 29, 2014 Share Posted May 29, 2014 "The usual reason for a level indicator LED not illuminating has to do with the float in the cassette, but it should be possible to test the indicator with a magnet as you've been doing. " Floats in my cassette don't need a magnet to test them! Link to comment Share on other sites More sharing options...
cruiser Posted May 29, 2014 Author Share Posted May 29, 2014 Thinking about it, you're spot on. I've never needed the warning light in our eight years (so far) of happy camping. I know roughly when to keep an eye on the level. Also the weight when it's left too long, leaving me struggling to the disposal point whilst trying to look dignified (knowing herself is peeping out of the camper p***ing herself laughing). So I'll carry on as before, as they say over here, God sent no greater loss..... .........but I'm still puzzled as to why a proven 12 volt feed won't light a proven working LED. Link to comment Share on other sites More sharing options...
cruiser Posted May 29, 2014 Author Share Posted May 29, 2014 Billggski - 2014-05-29 8:38 PM Floats in my cassette don't need a magnet to test them! Ha.....another Carry On fan. Oo-er missus! Link to comment Share on other sites More sharing options...
Derek Uzzell Posted May 30, 2014 Share Posted May 30, 2014 cruiser - 2014-05-29 11:40 PM .........but I'm still puzzled as to why a proven 12 volt feed won't light a proven working LED. As I understand it, there is no doubt that there's an active 12V supply on the input-side of the magnetically-triggered reed-switch and you've confirmed that the LED illuminates when powered by a 9V supply. I'd jury-rig the LED into the 12V supply on the input-side of the reed-switch and confirm that the LED illuminates. If it does, but, when the LED is connected to the output-side of the switch and the switch's operation is tested with a magnet, the LED does not illuminate, either the magnet-testing methodology being used is flawed or (despite the readings you obtained during magnet-testing that suggest the switch operates) there must be something wrong with the switch. It's a pity not to rectify this sort of problem, as a DIY fix SHOULD be simple and, even if a new reed switch were needed, the cost would not be high. Obviously it's possible to sidestep the problem as Had Enough does, but it's still useful to have a working level-indicator light. The following advice (provided by Thetford) is taken from a 2010 "caravantalk" forum-thread: "The level indication led works by a magnet in the waste tank connecting with the reed switch which illuminates the led. The end user can test the reed switch by passing a magnet across it. The reed switch is a small green circuit board situated in a stem in the holding tank compartment. If the led illuminates when a magnet is passed across it, it's likely that the float and / or magnet have become detached in the holding tank. If the led doesn't illuminate, this would indicate a problem with the reed switch or the control panel. Other points to check include to check the stem which holds the reed switch is correctly positioned and that the tank is correctly positioned when in situ." (I think Thetford's advice relates to the C-250 model toilet, but the general principles should hold good for a C-200 model, assuming that's what you have.) Link to comment Share on other sites More sharing options...
Keithl Posted May 30, 2014 Share Posted May 30, 2014 Cruiser, It sounds very much to me like you have a poor 12v feed to the reed switch and LED. The voltage should not slowly rise or fall, it should be circa 12v and nothing else. Can you try powering up the circuit from a stand alone battery or long wire from say the cigarette lighter socket? Obviously disconnect the original feed first! Keith. Link to comment Share on other sites More sharing options...
Guest Had Enough Posted May 30, 2014 Share Posted May 30, 2014 cruiser - 2014-05-29 11:40 PM Thinking about it, you're spot on. I've never needed the warning light in our eight years (so far) of happy camping. I know roughly when to keep an eye on the level. Also the weight when it's left too long, leaving me struggling to the disposal point whilst trying to look dignified (knowing herself is peeping out of the camper p***ing herself laughing). So I'll carry on as before, as they say over here, God sent no greater loss..... .........but I'm still puzzled as to why a proven 12 volt feed won't light a proven working LED. I'm described by my wife as a control freak with a touch of OCD and I'm the sort of person who would try hard to fix something, but my point was that sometimes you have to stop worrying about something so insignificant and something that you can easily manage without. Yes, have a go at fixing it and you'll get a degree of satisfaction if you manage it, but eventually if you have no luck treat it in the same way as occasional rattles in a motorhome. If you tried to eliminate them all you'd go crazy! Link to comment Share on other sites More sharing options...
cruiser Posted May 31, 2014 Author Share Posted May 31, 2014 OK, I decided to leave it alone....life's too short etc. Just thought I'd have one more stab at it yesterday, there's two hours of my life I'll never get back. No further forward, so here's a brief resume..... BTW, the slow rise in volyage must have been a sticky switch, it's now instant. Here's where I am now..... I cut the two feed wires to the LED and fixed a magnet to the reed switch casing and put a meter across the feed wires.. 12v ok, but if I put the LED or even a 12v bulb across at the same time, the voltage drops to zero. I put the (polarity conscious) LED across the cig lighter, all good. If I put the LED between the original feed and an earth, it works.The other wire in the original feed pair,which I assumed was an earth, doesn't seem to do anything, It doesn't show any reading between it and earth etc.. So I thought I'd cut the switch wires and test them. I assumed it would be a no-magnet/ open, magnet /closed. But no, there's no reading from the switch at all. To re-cap, if I put the magnet against the switch, 12v appears across the two feed wires. If I put the working LED across the same wires, nothing happens. Time for my tablets I think. And a lie-down. Link to comment Share on other sites More sharing options...
Dr Dave Posted May 31, 2014 Share Posted May 31, 2014 There is a high resistance somewhere probably the reed switch itself. As the meter puts virtually no load on the circuit it will read 12 volts as soon as a minimal load like the led is attached the high resistance cannot pass the required current so the voltage drops to zero. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted June 1, 2014 Share Posted June 1, 2014 A Thetford C-200 toilet (I have prompted you unsuccessfully several times for confirmation regarding which model of toilet is fitted to your Rimor :-( ) has just a simple reed-switch with its internal electrical contacts normally open. When triggered by a magnet the contacts close and the 12V power that's being supplied to the switch by one of its two cables passes through the switch and 'out' through the other cable and on to the LED. Instructional drawings for fitting a replacement switch are provided here http://www.bradtech.ltd.uk/products/T23714%20reed%20switch0001.pdf and (as far as I can see) it doesn't matter which of the switch-cables is used for '12V power in' or '12V power out'. Testing should merely involve a) running a 12V supply to the LED and on to earth so that the LED illuminates. b) introducing the reed-switch into the 12V supply to the LED (which should stop the latter illuminating). c) applying a magnet to the switch, which should cause the switch's contacts to close and the LED to illuminate. If c) fails to cause the LED to illuminate, then the switch is at fault. It should not be necessary to resort to use of a meter for diagnosis as the circuit is so simple. Link to comment Share on other sites More sharing options...
cruiser Posted June 1, 2014 Author Share Posted June 1, 2014 Dr Dave - 2014-05-31 4:11 PM There is a high resistance somewhere probably the reed switch itself. As the meter puts virtually no load on the circuit it will read 12 volts as soon as a minimal load like the led is attached the high resistance cannot pass the required current so the voltage drops to zero. I think that could be the answer. I'll check out new switch prices etc and take it from there. BTW, Derek....if you glance back through the thread, you'll see that I have already followed that procedure. The confusion arose from the fact that the closed switch clearly showed 12 volts (on a multimeter) passing the switch, but the (working) LED would not illuminate. Can't really see why the model of toilet would have any bearing on the problem, but thanks for your input. Link to comment Share on other sites More sharing options...
Keithl Posted June 1, 2014 Share Posted June 1, 2014 cruiser - 2014-05-31 1:47 PM If I put the LED between the original feed and an earth, it works.The other wire in the original feed pair,which I assumed was an earth, doesn't seem to do anything, It doesn't show any reading between it and earth etc.. I would read this as the earth (or lack of) as being your fault! Have you tried substituting a known good earth? Keith. Link to comment Share on other sites More sharing options...
George Collings Posted June 1, 2014 Share Posted June 1, 2014 Keith, You have beaten me to the punch. For most electrical faults rather than check the power supply I now check for earth continuity first. I think its because earth points are often in relatively exposed position where dampness causes corrosion between different metals. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted June 2, 2014 Share Posted June 2, 2014 cruiser - 2014-06-01 10:34 AM ...Can't really see why the model of toilet would have any bearing on the problem, but thanks for your input. The very first sentence of my initial response to your inquiry contains the assumption that your toilet is a Thetford C-200 model, but that 'guess' was based on the stated age of your motorhome and the fact that the toilet has an LED level-indicator. It's probably a reasonable assumption but, even if the toilet were a C-200 model, there's still the potential for variation in the level-indicator system. There are four variants of the C-200 design - two (CW and CWE) have an integrated flush-water tank, one (CS) takes its flush-water from the motorhome's fresh-water tank and has an integrated control-panel, while the fourth (S) is technically similar to the CS model but has a separate control-panel. The S, CS and CWE models all flush electrically and have the same type of level-indicator system. Conversely, the C-200 CW flushes manually and its level-indicator LED is battery powered. I don't know if the model of Thetford toilet has any bearing on your problem, but there might be a known fault with the LED level-indicator for certain C-200s and not others and, if it were known which model yours is, researching on-line would be simplified. As an accurate definition of the model of toilet at the start of the forum-thread had the potential to help matters, it seemed a sensible thing to ask for. The reason I highlighted the simplicity of the testing procedure was that, whatever you'd been doing, it had not pin-pointed the cause of the problem. You know that the LED can illuminate and it would seem that the reed-switch might be in working order. The suggestion now is that, when the LED is installed in the toilet, the wire leading from it that should go to earth is not earthing. Plainly if that's the case, the LED and switch can be in full working order, but the LED cannot illuminate due to the lack of earth. I'm not sure from your description whether your testing has simulated the toilet's wiring or used the actual toilet wiring. If you've been simulating the system, with a 12V supply feeding the reed-switch, the switch wired to the LED and the LED wired to earth, and using a magnet to operate the switch fails to cause the LED to illuminate, then the switch is probably duff. If a simulated system allows the LED to illuminate but, when the LED and switch are wired-up in the toilet itself, the LED wiill not light up, then the 'no earth' diagnosis is probably correct. Link to comment Share on other sites More sharing options...
mthomson Posted June 7, 2014 Share Posted June 7, 2014 I would concur with those who have suggested that the best way is simply to open the blade and look in. Furthermore, if you're on the move rather than settled on site for a few days, you may have limited opportunities for emptying the cassette, especially if relying on the aire and Stellplatz facilities in Europe, as they don't all have fresh water and emptying facilities. I like the suggestion of putting in half the fluid and emptying the cassette every day, although it might be as well to check whether it's a good idea to pour the toilet fluid down past the blade. I'm not convinced about level displays for fresh and grey water either, and tend to rely more on memory and fairly rapidly gained experience of running short of fresh water or having grey water appear in the shower tray! Link to comment Share on other sites More sharing options...
enpiste Posted June 28, 2014 Share Posted June 28, 2014 the level in a toilet cassette can be very important .... I normally use a stopwatch and some maths..... but the basic principle is count the time before the splash..... i.e. one thousand ... two thousand etc...... as the time gets shorter it means you are nearer the top. As for standing up ... well that can be gauged by change of pitch.... I have a b flat tuning fork handy ... when checked against this I know I am near the top. I have heard that google are bringing out an APP for android phones that will let you know when your cassette is full even if you are nowhere near your motorhome .... Hope this helps. Link to comment Share on other sites More sharing options...
Tracker Posted June 28, 2014 Share Posted June 28, 2014 enpiste - 2014-06-28 12:55 PM I have heard that Gurgle are bringing out an APP for android phones that will let you know when your cassette is full even if you are nowhere near your motorhome . Flushed with success? Never do Turday what you can do in a wee while? Link to comment Share on other sites More sharing options...
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