After four years of troublefree use, a fault developed overnight. The PID display started showing rapidly fluctuating temperatures, and then the brew boiler cut out - it must have overheated due to the incorrectly measured temperature. Having removed the case, I find that there must have been a long-term gentle leak from the threads of the probe mounting, with limescale around it, and either the probe has now failed or is being insulated by a layer of scale.

I've seen a few posts here and elsewhere, with people cleaning or replacing the probe themselves. I know it's a 17mm fitting, but access is very tight without removing several other components - for example a coiled copper pipe transmitting pressure is very close to the probe, and naturally I would prefer not to damage that or anything else I removed the stat cut-out, which was easy, but still no room for my spanner.

If anyone is able to provide some advice for ideal tools to use, and steps to follow to gain good access, I'll be very grateful!

adrianr wrote:If anyone is able to provide some advice for ideal tools to use, and steps to follow to gain good access, I'll be very grateful!

I personally would disconnect the wires from the pid and use a box spanner the correct size, feeding the probe wires through (or bunched inside). You can then use a spanner, tommy bar whatever on the top and also are able to shock it free if there is a lot of thread locker...either with an electric impact wrench or tapping with hammer etc..

Then clean the casing and test the probe.....as the probe is embedded within it.

I BELIEVE your temperature sensor (when removed and cleaned) looks like this:



It is likely a 50K ohm negative temperature coefficient (NTC) thermistor. So, before you remove it, undo the electrical connection between it and the PID unit and measure the resistance at room temperature. It should be around 50K ohms. Once removed, you should be able to effect a good seal with the boiler using a Teflon washer.

Thanks a lot for answering, Gents.

Good tip, Eric, to test the probe, and how to better seal it. Yes, that's exactly the one.

Dave, a box spanner - obvious now you've pointed it out:-) But not before, to me. I've ordered one for use next weekend. Still likely to be a clash with the manometer tubing,so think I need to either try gently bending it out of the way, or undo one end with the expectation it'll be springy enough due to it being coiled several times in to a spiral. Does anyone have any experience doing that, and of any hazards or requirements when reconnecting?

Undo the manometer tube from the fitting to the rear of the boiler (as viewed from the front of the machine and it will quite easily move out of the way so you can attach the box spanner. When re-attaching, just tighten enough so it doesn't leak...no sealant or tape is required/should be used on the fitting/threads.

Thanks again, Dave! Appears to be straightforward, then...

Dave, your tips all worked out a treat. Hardest part was disconnecting the connector of the thermistor, as in a very tight location without wanting to get in to further dismantling! Using Eric's tip about the resistance, I think I've nailed the fault - room temp gives 5M ohms, and in a mug of boiling water it only went down to 500K ohms, but more importantly the wires appear to be damaged internally at the thermistor end, as I had to carefully move the wires to get a sensible reading at all, and if shaking a little the resistance was constantly variable but effectively not making a circuit most of the time. With a lot of scale both on the inner and outer surfaces, I assume some found it's way through to cause damage to the wire's insulation or has stretched the core.

So, time to order a replacement from Bella Barista, as it appears most practical and cheaper to order from the UK for NL delivery, with little alternative showing up on line.

Thanks again, and I'll update to close the thread when all back together and hopefully functioning normally - probably this time next week.