The heating has suddenly stopped working today. We have a combi boiler and the hot water still comes on instantly when we use the taps.

We have recomissioned the thermostat (Sunvic TLX7506 RF digital room thermostat) to ensure the signal is being received and that seems ok. The thermostat is showing that heating should be on.

The timer is set correctly and there are no fault lights flashing on the boiler. We have also increased the pressure as this had fallen below 0.5. The only thing that doesn't seem right is that the TEST button does not make the boiler fire up (usually it does).

Can anyone help??

Tina, January 2009

i have the same problem this moring - i called Sunvic Controls Ltd who make this thermostat today and your boiler is okay its the receiver thats broken so you will need a new one. Suggest trying ebay on B& Q - large stores only - start at about £60.

hils, March 2009

if the dhw pin was stuck out the the tap would be lit up on the boiler,i would isolate electrics drop front cover remove pcb cove and put a link on the room stat wiring to be sure theres no problems with externals,unless the radiator light is coming on with the programmer

jim, February 2009

what area

b, January 2009

Thank you for your advice but i now think it is time to call the engineer in to have a look.

Tina, January 2009

if the boiler is not even trying to start it may be the
external controls.
the only to test the room stat and timer is to disconnect it at the boiler and do a continuity test
with a multy meter or link the terminals on the boiler.

b, January 2009

The boiler is set on the timer mode so it should only come on in the morning and evenings and the thermostat is set at 21 degrees and the current temp is 14 degrees(cold).

The white pin on the timer is situated in the middle as always and i have even tried it in constant mode.

The test button on the thermostat that usually works and fires up the boiler is no longer working but did a days or so ago and i have a feeling it may be related.

Tina, January 2009

is the heating set to constant and the room stat on max

b, January 2009

no, its still not working :o(

Tina, January 2009

does the heating work now

b, January 2009

Hello, i have checked the pin and that does not stay out after the hot water has been turned off so that seems to be working ok.....any more troubleshooting tips would be greatly appreciated.

Tina, January 2009

2 screws on the bottom panel undo them a bit
and lift the top panel up and off then the undo the 2
screws all the way intil the bottom panel drops down.
behind the bottom panel on the left hand side is the
diverter valve, it brass. on the end is a switch.
when a hot water tap is turned on a rod will come out
and push the switch, some times that rod stays out.
if it has push it back in. turn the electric off before you start

b, January 2009

If it is the diverter valve sticking how would i fix it.

Tina, January 2009

some times the diverter valve sticks in the hot water
position stopping the heating from working

b, January 2009

The dial is turned fully to the left and is on the heating and hot water mode

Tina, January 2009

could be stuck in hot water mode

b, January 2009