ACS Minima steam boiler overheating

alexgab

Hello,

I have an ACS Minima that I purchased back in January 2020. It’s been on a Meross smart plug for about 2.5years with no issues. Recently, the steam boiler started overheating consistently in the morning. The safety valve does kick in to release pressure, but it doesn’t stop heating or filling the brewer until reservoir is empty and throws an H2O error.

I initially took it into a repair shop. However, shop was not able to replicate the issue after 2 weeks of testing. I took the machine home and plugged it back into the smart plug and it overheats again the next morning. I removed the smart plug and it seemed to solve it. Steam boiler climbed to 124C and held steady.

However today, it overheated again (no smart plug). After turning it off, releasing steam through the wand, I turned it back on and it climbed from 100 - 124 and held steady. I’ve no idea what’s wrong. I did notice that even at 124C, there’s a slight hissing with steam escaping from the valves in the picture. I don’t think that’s normal behavior.

I’m new to actually tinkering with a machine, and the parts diagrams I’ve seen do not name the part, only the part number. Appreciate any help this group might be able to provide!

Cuprajake

Temp sensor is the red wire non circled with brass fitting, mine went so possible that

Elcarajillo

The temp/ sensor seems a common problem on different machines, I have replaced 2 and now keep a spare.
I believe at one time there was a faulty /defective batch.
Take great care NOT to twist the wire when /if replacing, especially near the sensor.

alexgab

Appreciate the insight! Where can I get a replacement temp sensor? The retailer I purchased the machine from doesn’t carry the exact part number and I’m afraid I’m a bit lost on where to go for parts in general. (I’m based in the US).

DavecUK

alexgab You can use most sensors, go for one of the stainless ones, ACS changed to them because they use potting that doesn’t expand/contract and eventually break the connections inside.

https://clivecoffee.com/products/profitec-temperature-sensor-1-4

this would work fine

alexgab

Thanks, @DavecUK! Sort of related, what is the part I circled on the right of the picture called?

I noticed that it hisses with a slight leak when it comes up to temp. Is that normal or should I look to replace that as well?

DavecUK

alexgab I noticed that it hisses with a slight leak when it comes up to temp. Is that normal or should I look to replace that as well?

Where exactly is the lever probe fitting leaking from?

Rob1

It’s the level probe and it’s not normal for it to leak. There shouldn’t be air escaping when up to temp and the vac valve closes. Possible boiler overfilling?

alexgab

That seems possible. How would I check for overfilling? Do you know if this work as a replacement on the ACS as well?
https://clivecoffee.com/products/pro-300-steam-boiler-level-probe?_pos=3&_sid=bb12b4f39&_ss=r

alexgab

@DavecUK from what I can tell it’s the from the base where I circled it. I see some discoloration (corrosion?) around it too.

DavecUK

alexgab Then the fitting needs removing from the boiler, take the level probe out first, just loosen the small nut (it won’t be tight), then slide it out, when replacing, don’t do the little nut too tight. Remove the main fitting from the boiler, clean threads, wrap with 7-10 turns of PTFE tape and refit.

The fitting will be really tight and you will have to shock it of with sharp raps to loosed the permanent thread lock. Be sure to tell ACS if it’s super hard to get off. I asked them to use semi permanent flexible thread lock middle of last year and I think by Last October (22), they have moved to that and/or PTFE tape.

alexgab

I’ll order the temp sensor, try the repairs and report back!

alexgab

Just wanted to report back that I replaced the temp sensor and cleaned up the boiler level probe and all is well in the world again. Thank you everyone for your help and advice!

The level probe was actually not hard to remove, I did notice that there was very beat up residual PTFE tape around the threads and suspect that disintegration was causing the whistle leak.

DavecUK

alexgab The level probe was actually not hard to remove, I did notice that there was very beat up residual PTFE tape around the threads and suspect that disintegration was causing the whistle leak.

Someone may have wrapped it the wrong way! Glad it was an easy fix.