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hymer b564 1994 boiler location

jo scott

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Hi Jo. Have you just bought another van cos your profile mentions a Carioco 644?


Anyway, I'm not that familiar with the B564 but Hymer tend to install the boiler at the bottom of the wardrobe, so as to keep the clothes nice and warm.


Suggest you first look in that area. Failing that, look on the outside of the van - there will be a vent which provides fresh air to the boiler which also doubles up to get rid of the exhaust gases.



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its my mates van,


(still cant see boiler but found fuse switches which now allow truma control panel to show green light so guess thats working.. but no water coming out of the pipes.


and only cold air from the blow heater.


(and yes we dont have the carioca (our 'bling' van .. now have a fiat autosleeper rambler

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The external vent on the van should be in close proximity to the boiler on the inside.


The boiler dump valve is probably in the open position - hence no water at the taps. Once you find the boiler, check the dump valve to make sure it's in the closed position.



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mmmmm ... and what does a dumo valve look like... ive found a yellow toggle on a pipe. it swivels freely or can be depressed ... just like me!.. ive been reluctant to push or lift it too much for fear of breaking. but i'll nip out after lunch ...pea and bacon soup just made... cheers
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I guess you have now found the location of the boiler in the van.


If so, perhaps you could tell us the model number which should be shown on the side of the boiler. I assume it is a Truma boiler of some kind. Maybe you have the instruction manual?


Your boiler is at least 22 years old. Later generation Truma boilers have automatic ignition and controlled by a printed circuit board (PCB).


Normally (at least in later models), if the boiler does not ignite automatically, the control panel turns from a green light to a red light.


You say you have a green lights but no hot blown air. The manual usual has a help guide to resolve any non operational problems.


Maybe there are other forum members on here who are more familiar with this age of boiler and can help.

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This advert is for a 1994-registered Hymer B564




The 2nd photo shows the vehicle’s right-hand side and the ‘flue’ of a Truma “Ultrastore” water boiler (probably the gas-only version for a 1994 Hymer) is visible above the back of the right rear wheel. (I see that the boiler has been found and I’m guessing it was secreted in the base of a wardrobe.)


The 5th photo shows the motorhome’s interior and indicates that air-heating is via a Trumatic “S” 3kW-output convector fire (its roof-mounted ‘chimney pot' is visible in the 2nd photo) and - from what Jo says - the heater probably has an Airmix/Trumavent fan-unit to provide blown-air.


Installation/Operating instructions for Truma equipment (even elderly equipment) can be found/downloaded from here




The Operating Instructions will normally contain trouble-shooting advice, though this may be pretty minimal for older equipment as this was much simpler than the present stuff.


(Note that, if your web-browser is set to block pop-up windows, you will need to turn off the blocker to allow the Truma documents to be read.)

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oddly .. we still cant see a boiler. ive found pipes with a yellow toggle switch which we have worked out is the dump toggle. so with that altered, we have water flow.

plus i found a fusebox with two switches in Off position - altered those = water flow / and green light on Truma Boiler control.. so hot water.


as for the heater - with the cover off . we revealed a serial number plate but too rusty to read.

It has grey metal fins and right at the bottom a tiny nodule with a bulb that goes red when we fiddled with the 1- 9 thermostat control.


that thermostat control dial can be pushed down .. so i wonder whether that would be some form of ignition? my friend tells me the heater was working when they collected the van 2 weeks ago.... unfortunately the seller is away,


Thanks for the input...

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This Truma Operating Instructions document should be applicable to the Hymer’s water-bolier (assuming the boiler is the original one, of course!)




If you look at Page 3 of the document, you’ll find a reference to a Safety/Drain valve. This is the 3-position lever-operated yellow ‘toggle switch’ that you’ve spotted. It is designed to be operated manually to drain the water-boiler (and perhaps the motothome’s complete water system) or to automatically reduce the presure in the water system in the (unlikely) event that the pressure becomes excessive.


You’ll also see from the drawing in the Operating Instructions document that the water-boiler is attached directly to the external vent/flue. The external vent/flue is referred to by Truma as the “Cowl for combustion air intake and exhaust gas discharge” and may have a protective ‘cowl cap’ that must be removed before the boiler is operated on gas. (Don’t be surprised if there is no ‘cowl cap’ on the external vent/flue, as they often break or are left off permanently.)


As the boiler is attached directly to its external vent/flue, once you have established the external position of the vent/flue in the Hymer’s side-wall, the boiler itself MUST be inside the motorhome and located immediately behind the vent/flue.


As Robbo advised earlier, it was commonplace for Hymer to install the boiler under the vehicle’s wardrobe and (from the photos of the B564’s interior I referred to earlier) it certainly looks like that’s where a 1994 B564’s boiler should be anticipated to be.


However, don’t think that, if you open the wardrobe you will necessarily find the boiler in plain view, because Hymer are not like that! You may find that the boiler is totally enclosed and to gain access to it involves lifting a ‘hatch’ or unscrewing a piece of furniture-board. But - once you’ve identified the position of the boiler’s external vent/flue - the boiler will be on the other end of the vent/flue even though you may not be able to see it straightaway from inside the motorhome.


As far as the air-heater is concerned, this Truma webpage




carries pictures of older Truma convector heaters and you may be able to use the pictures to decide which heater your mate’s Hymer has. Some of these heaters use a piezo igniter to light the gas




Some have an igniter powered by ‘torch batteries’




Some are connected to the motorhome’s own 12V system.




As a “tiny nodule” went red when you fiddled with the temperature control, this may indicate that the heater is the last of the three types.


It should be possible to identify which type of heater your pal’s motorhome has by comparing it with the drawings in the Truma Operating Instructions. However, as the serial number plate cannot be read, if it’s practicable it might be sensible to wait until the seller can be contacted to talk your friend through the heater’s operating procedure. (Best not to play about with a gas appliance too much if you don’t really know what you are doing...)


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