Jaguar boiler still not working

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10 Nov 2005
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United Kingdom

I've posted about this before and had some good and helpful advice. Unfortunately it hasn't worked and both myself and British Gas (who have been out FOUR times now) are baffled. Can anyone help...

There is an intermittent fault with my boiler (a Jaguar). It is failing to stay on. The flames are visible as it tries to 'fire up' but then they cut out, then come back on again and again. Yesterday, following the latest visit from BG, it stayed on all evening and I had a lovely hot bath. This morning I woke to the problem all over again. BG are due to come again on Monday but I thought I'd I'd if anyone had any suggestions. So far we've had the PCB, Air-Pressure Switch and the Flame Sensor replaced, but it doesn't seem to have made a difference.

Failing any advice, can anyone tell me if they know of a plumber in the West London area that knows something about Jaguar boilers (rebadged Glo-worm I'm told)?

Finally, am I just wasting my time trying to sort this out and if so, how much should I expect to pay to get a new (decent) boiler fitted?

Thanks in advance
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Check ther boiler has a good earth. Ive change a couple of sticking gas valves on the early Jaguars as well.
Would a poor earth cause the problem (bearing in mind it sometimes works fine)? I'll have a look at the valves, but the things's only 18 months old (I think).
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The Jaguars are perfectly reasonable boilers for anyone who takes the time to understand them.

There would seem to be two prime suspects, the air pressure switch and the flame detection. Merely changing parts does not eliminate either of these. A competent engineer can confirm the APS operation and the flame detection.

Both of these are sensitive as they are safety devices! And yes the earthing is essential for flame detection.

The SIT 845 gas valve used in these boilers do stick but thats more prevalent during hot weather and would cause a lack of firing up rather than the "going out" which you seem to be saying.

To correctly diagnose the problem attention has to be paid to fine detail. Since BG has started then they should finish it!

Tony Glazier
Thanks for the replies guys.

To be honest I don't know very much about boilers (although that's changing with each day the thing doesn't work!).

The BG engineer seems to know what he's doing, but unfortunately everytime he comes the boiler's working so he's just relying on what I tell him.

If it's a valve problem, is it possible it would work sometimes and not others?

What could be causing the APS or the Flame detector to not operate (especially as they were only fitted yesterday!)?

Sorry for all the questions, but it's been like this on and off for three weeks now, and it's really cold out...
It could be the cvi unit playing up this affects the fan and sensing leads as well as the gas valve
The Jaguar has an overheat device located on the flow to the heat exchanger, i've changed gas valves but the fault re appears. Get BG to check the wiring harness to the overheat stat as they are prone to burn or lack continuity giving your fault.
The o/h stat is on the flow from the primary HE. However they are a manually reset unit so the part itself is not tripping but it or the connectors could be faulty.

Sticking gas valves can stick at any time but this is more likely when the boiler has not been used for several hours.

Again he seems to be saying that it "goes off" rather than fails to start.

Its a pretty simple and straightforward boiler really!

Tony Glazier

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