Green Light constantly on (familiar topic)

Moved into the property 2 years ago, recently noticed the dreaded buzzing noise on the Boilermate II so being a novice, I checked this forum and replaced the pump delay timer PCB and pump drive PCB (cos someone suggested best to replace them at the same time given same age) AND the Capillary Thermostat - the latter because the green light is constantly on. While the buzzing noise has gone, the green light is still on 24/7 as well as the pump at the bottom, which is generating lot of heat in the airing cupboard and a real nuisance in the night due to the noise of the pump (lately been turning down speed of pump to get some respite as I work shifts). I have unsuccessfully tried following the instructions - turning the Vaillant boiler to max temp and turingn down the dial on the front of boilermate II. No problem with the hot water and heating. I can now only suspect the tank needs descaling and considering replacing altogether at great expense. Any advice will be greatly appreciated.

Hi,

Check that the Capillary thermostat is actually working this will require a volt meter, if it is working OK then check the temperature of your store water, use a digital thermometer in the dry pocket that the capillary stat sits in, It should be reading just over 70 degrees. If it is lower than 70 degrees then check your pump speed setting of your boiler pump, Increase it if necessary.

You may require a new larger pump 15/60 which would be cheaper than replacing the system, if you do replace the pump i would suggest a full drain down to clear any debris in the cylinder.

Hope this helps!

Kind regards

Gary
MK Group Ltd

Gary

Many thanks for this. I will look into it myself if I can. Previously, I got someone to help with replacing the parts, having bought the parts myself online. But I need to get this sorted out one way or another as the green light is on 24/7 and the pump is running at highest speed (hence the heat in the airing cupboard).

Does MK Group cover as far as London SW17 (Tooting Bec) or whenever you're next in the South London area?

Best regards
Jimmy

Hi Jimmy,

Yes we cover SW17,

Call our office to book an appiontment. 0870 80 31 999.

Kind regards

Gary

Gary,

Could you explain how you check the Capillary thermostat? My understanding of these devices is that they change they resistance under heat.

But how do you test them using multimeter?

I would appreciate some advice with this matter.

I have a similar problem to JT07 posted on Mar 9th 2012 (below). In short I have an old Boilermate II (approx 20 years old) and after draining the CH system down to fit a gate valve and fixing a resulting cold feed blockage, I noticed that the green light is on constantly and the boiler pump runs constantly. In addition, the boiler fires up every 2 min and runs for 7 secs briefly reaching its max temperature of 80 degrees C before shutting down. My feeling is that this is a Boilermate fault rather than an inability of the boiler to supply heat or a blockage in the pump. I would be grateful for any advice on this before attempting/commissioning any repairs.

The Green light on my Boilermate 2 was on all the time too- and the primary pump was always running.. The pump overrun board was fine, so was the thermostat...- (I did the testing..)
Eventually I tried turning down the big knob in the middle of the unit from maximum to about 90%.. The unit made a 'click' noise as the new setting seemed to take effect and the green light that registers when the unit is demanding heat went out!
Now the primary - (boiler)- pump goes off about 5 mins after the boiler cuts out... - So the system seems to be functioning correctly!

I could not find an explanation in the instructions that covered this.. So I thought Id share it..- It took me long enough to work it out!
I turned the system up to max about a month ago when the cold snap hit..- we have a shower that dispenses a lot of water and when it was on at the same time as the rads the shower was running cold sometimes..

I appreciate that there may be another issue going on here.. Why the unit is demanding heat all the time when the setting is on Max I do not know- It must get hot enough... However the system seems to be functioning correctly now.
Its worth trying this before spending money!
Hope this helps.