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Truma Frost Control


Way2Go

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When I winterised my motorhome I turned the switch and instead of it dumping water on the ground, nothing happened. I retried it and the switching and button popping out all seems to be working correctly except it will not dump any water.

 

The only way I could empty it was to run the water pump and it then dumped the water so I turned the pump off again.

 

Thinking it was faulty I thought I’d replace it with another one but I’ve just checked and they are €139 ?? So has anyone ever come across this before and know of a fix? I’m assuming the pipe isn’t blocked otherwise it wouldn’t have been dumped with the pump running.

 

I’ve seen several references to them leaking water (and the old peg trick) but have found a solution to this problem.

 

Many thanks for any anticipated advice.

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Couple of things to think about.

First, had it any water in it? As then the pump might just pumping new water into it.

Second, Could it be the water won't flow without help? Try turning pump off, then opening all taps.

p.s. regarding first point, it wouldn't surprise me at all if it hadn't already dumped the water.

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colin - 2021-01-22 2:54 PM

 

Couple of things to think about.

First, had it any water in it? As then the pump might just pumping new water into it.

Second, Could it be the water won't flow without help? Try turning pump off, then opening all taps.

p.s. regarding first point, it wouldn't surprise me at all if it hadn't already dumped the water.

Well, everything had been working up until that point and the system had water in it. I started emptying the fresh water tank, opened the taps and I went to the Truma valve like I have always done and activated the water dump so I could winterise it. I checked underneath and saw no water coming out so reset it and reactivated the dump with the same result.

 

To empty the system all I could think of was to run the water pump and try to force it out. I then noticed the water level in the small header tank started going down and water was being dumped on the ground.

 

When the water flow stopped I turned off the pump and the header tank was empty.

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colin - 2021-01-22 4:28 PM

 

I think I'd be tempted to refill system and try again before buying a new one. It might have been 'sticky', or it might have been a blockage such as a insect hibernating which needed clearing.

Thanks for your reply.

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An example of the Truma FrostControl safety/drain valve is on the 1st image attached below.

 

Closing the valve involves turning the blue rotary switch (green arrow on image) on the top of the valve until it is in the postion shown on the photo and then pressing in the blue push button (red arrow on image) on the front of the valve until the button stays in. To open the valve, just turn the blue rotary switch through 90 degrees which should cause the blue buuton to pop out.

 

This (French) YouTube video

 

 

advises on how to disassemble a FrostControl valve and shows its internal workings. I’ve never taken one of these valves apart, but the video seems to show that control of the water passing through the valve (or down its drain-hose) is via a black rubber seal that is pressed against the 3-way (inlet/outlet/drain) plastic component that’s held on to the end of the valve by a simple U-shaped wire clip. Removing the 3-way ‘thingie’ will allow the condition of the rubber seal to be checked and, if the seal has lime-scale or muck on it, just cleaning this off could cure your drainage problem. (If the seal is damaged, I don’t think it is available as spare part.)

 

(The primary purpose of the French YouYube video is to show how to convert a FrostControl valve so that it retains its overpressure capability but removes its temperature-related operation.)

 

As Way2Go has said "the switching and button popping out all seems to be working correctly except it will not dump any water” it’s quite likely (as colin has suggested) that there’s a blockage. Removing the plastic 3-way fitting (2nd image attached below) is probably the first thing to do. In principle (as the video demonstrates) this is a simple task, but how easy it would be to do in practice will depend on how accessible the valve is.

Truma-FrostControl.jpg.7dfc7de5c0d4d61297e6102757e8cf11.jpg

1955361447_3-wayfitting.png.27e00aeee075c97ea9c13b557b3d71f6.png

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An instruction manual for the FrostControl safety/drain valve can be found here

 

https://www.manualslib.com/manual/1481167/Truma-Frostcontrol.html#manual

 

The most recent incarnation of Truma’s simple (much cheaper) lever-operated safety/drain valve has a white body with (for the John Guest version) blue inserts. (Image on this German advert)

 

https://www.intercaravaning.de/shop/de_DE/Wasserteile-C-3402-11525/Ablassventil-JG-12-mm-28-bar-213832.html

 

Obviously, if the lever-operated valve is chosen, the automated frost protection that the FrostControl valve is designed to provide will be lost.

 

The FrostControl valve has an ‘over-pressure’ setting of around 3.5bar which allows the pressure in the motorhome’s water system to be intermittently reduced automatically during the water-heating phase. The lever-operated valve with a YELLOW lever has a similar ‘over-pressure’ setting of around 3.5bar, so should be suitable for use with a Truma Combi heater. However, my understanding is that earlier versions of the lever-operated valve with a RED lever had a lower ‘over-pressure’ setting of around 2.5bar and would not be Truma Combi-compatible. (I’m not sure if the red-lever valve would still be on sale nowadays, but one never knows...)

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