Portrait photo of Mike Bryant, AKA Mike the Boilerman

Mike the Boilerman -

Your Gas Safe Registered boiler 

and central heating repair technician in west Berkshire. Willing to travel :)



I am still carrying out house visits. Full details explained


(Last updated 21st April 2021)

Glow Worm Ultimate:

I like the Glow Worm Ultimate. Is a very good boiler in my personal opinion. Simple design, reasonably fuel-efficient, reliable and generally easy to mend if it goes wrong. All commonly failing parts are still freely available despite it being quite an old model. If yours has a breakdown and needs repairing call or text me on 07866 766364. I have most parts for this boiler in stock so a rapid fix is usually available.

The Glow Worm Ultimate is a non-condensing boiler which was manufactured from about 1990 to 2003 when the regulations changed and condensing boilers because compulsory for new installations. Production naturally stopped as the market for non-condensing boilers vanished. 

Owners of Glow Worm Ultimates are increasingly being advised by younger gas technicians to replace them for no reason other than that they are old. Difficulty in obtaining parts is sometimes cited but parts in my experience are freely available from any heating spares merchant.

What to check if your  Glow worm Ultimate breaks down:

There are a few basic things the user can check before (possibly unnecessarily) calling out a repair technician:

1) The overheat protection thermostat. This boiler has an overheat protection thermostat which might occasionally trip. Find and press the ‘reset’ button. Slide the bottom cover off (pull it towards you) to expose the user controls, and the reset button is If it clicks in the boiler will probably start working again. The button is shown in the diagram on the right. (Taken from the boiler manual.)

2) Check the control thermostat knob (also shown in the diagram) is not set to zero. 

3) Check you have the heating and hot water turned ON at the central heating programmer or time switch.

4) Check the room thermostat is turned to a high setting.

If none of this helps then you can be certain there is a fault and you haven’t overlooked something trivial. I suggest calling out a boiler technician to trace and fix it. The most common faults I encounter on a Glow Worm Ultimate are as follows:

1) Control board failure

2) Blocked pilot light jet

3) Main burners chattering on and off 

4) Ignition electrode erosion so pilot fails to light

This is a particularly straightforward boiler to fix usually, so if you'd like me to mend your Glow Worm Ultimate, feel free to call, text or WhatsApp me on 07866 766364.


Line diagram of Glow Worm Ultimate gas central heating boiler
Glow Worm Ultimate boiler - diagram showing location of overheat reset button.
Gas Safe Register Logo 2

Copyright Michael Bryant 2021

Site first published 16th January 2004

Last updated 26th April 2021

Gas Safe Register 197499, CIPHE registration number 56207

Chartered Institute of Plumbing and Heating Engineering logo 2

This website makes use of cookies. Please see my privacy policy for details.