# recurrent A2 error (brew temp sensor fail)



## emradguy (May 24, 2014)

First off, I want to say thanks to DavecUK for helping me on CG numerous times, but particularly yesterday with my broken resettable limit stat issue. Now, on to the current, pressing, issue...

About 6 weeks ago, my brew temp sensor failed. The temp was fluctuating all over the place ranging between 180 or so and about 220 or so within second. It was just jumping around all over the place erratically. The next time I turned the machine on, I got an A2 error on the PID display - go figure, huh? I replaced the temp sensor with a new one and everything was fine...untill yesterday...

The PID came up with the A2 error again! I unplugged the machine, removed the sensor and cleaned it thoroughly with 600 grit sand paper (as there was a film of oxidation on it, and a few scattered scale deposits), screwed it back in, and then powered up the machine. I let it run for about 20 minutes, since it was still warm when I did the work (not dangerously warm - but it came to temp within about 2 minutes), then pulled three doubles. After letting it run for another 5-10 minutes and seeing all was normal, I turned it off. This am, when I went downstairs, the A2 error was back!

If it matters...I'm operating in 20 amp mode on a dedicated 20 amp line (U.S. 115V). I have a Panamax surge suppressor and an Intermatic timer that brings it on around 5:30am for the morning warm up.


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## coffeechap (Apr 5, 2012)

Not being funny but Dave is once again your best point of call on this one is it is pretty much his brainchild


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## DavecUK (Aug 6, 2013)

A1 I think is the thermal probe (brew boiler for Duetto II), probe not present error message.

A2 Is the Probe short circuit message

(I can't remember which is which)

You can test this by removing the probe wires from the gicar and seeing if A1 is shown. It usually indicates some fault with the probe or the wiring to the probe. I believe you said you changed the sensor, but it might have been the case that nothing was wrong with it and there is some form of wiring fault (more likely). i'm also convinced that A2 can show without there being any direct short!

These connectivity faults can be in a number of areas


where wires enter the probe

where probe wires have a join (many model variants)

Where the probe wires enter the gicar pid

Within the gicar pid itself where the probe wire terminator is soldered to the circuit board


All quite fixable and are the first things I would look to before ever suspecting a faulty probe. I am not sure I have ever seen a proper faulty probe, it's usually the wiring.


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## emradguy (May 24, 2014)

Yes Dave, you are correct in yuor recall of the error codes. I looked them up yesterday. Glad to hear I may be able to fix it via electrical means, rather than ordering a part and replacing it.

Yes, I changed the sensor about 6 weeks ago, with a brand new one...and all was perfectly well after that until yesterday. I hadn't opened the machine since then either, so am a bit baffled how such a wiring fault could occur, other than power spikes, which I should be protected from via the Panamax...at any rate...I now have some direction to take in my investigation. Much appreciated!

Ron


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## DavecUK (Aug 6, 2013)

emradguy said:


> Yes Dave, you are correct in yuor recall of the error codes. I looked them up yesterday. Glad to hear I may be able to fix it via electrical means, rather than ordering a part and replacing it.
> 
> Yes, I changed the sensor about 6 weeks ago, with a brand new one...and all was perfectly well after that until yesterday. I hadn't opened the machine since then either, so am a bit baffled how such a wiring fault could occur, other than power spikes, which I should be protected from via the Panamax...at any rate...I now have some direction to take in my investigation. Much appreciated!
> 
> Ron


If I remember rightly, your variant has a plastic push fit connector in the wires between the probe and the PID, there might be a good place to look, as it might be knadgered (highly technical term I cannot explain).


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## emradguy (May 24, 2014)

DavecUK said:


> If I remember rightly, your variant has a plastic push fit connector in the wires between the probe and the PID, there might be a good place to look, as it might be knadgered (highly technical term I cannot explain).


That was the first place I checked yesterday when I opened the machine


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## emradguy (May 24, 2014)

Interesting reply from tech support at Chris' Coffee Service...

To paraphrase: The only thing that can give me the A2 error is the sensor. They're sending me a replacement.

Not that I don't trust you, Dave. Rather, I still plan to review the entire sensor circuit.

I will also report back on findings/solution (hoping there won't be any glitches that require additional advice along the way).

Ron


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## DavecUK (Aug 6, 2013)

emradguy said:


> Interesting reply from tech support at Chris' Coffee Service...
> 
> To paraphrase: The only thing that can give me the A2 error is the sensor. They're sending me a replacement.
> 
> ...


It could be...for sure, I can't remember which way round the error codes are, but I do know one of the error code can be caused by either a faulty sensor or bad wires..perhaps it's A1?


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## emradguy (May 24, 2014)

I should have asked this before, but well...I didn't think of it until now. As I check the circuit using my multimeter, what reading should I expect for normal?


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## DavecUK (Aug 6, 2013)

emradguy said:


> I should have asked this before, but well...I didn't think of it until now. As I check the circuit using my multimeter, what reading should I expect for normal?


God knows, normally your looking for a bad connection, open circuit.


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## emradguy (May 24, 2014)

Well, my courtesy replacement sensor arrived today from CCS, and...well, I'm enjoying a nice cortado! I'm thinking if this one fails within few months, I might just go ahead and replace my PID.


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## Combercoffee (Feb 12, 2011)

Just had the same error! Not being very technically minded is changing the temperature sensor simple to do? I have checked for breaks in the wires but cannot see anything obvious.


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## emradguy (May 24, 2014)

Sorry haven't been on the site for a while. I hope you got yours changed out. If not, or for anyone else who runs into this issue...You need a Phillips head screwdriver, a 10mm wrench for the case, and a 17mm wrench for the sensor.

Unplug the machine, then remove the cup warmer, top plate and outer case. If you're plumbed in, shut off your supply line.

I found it easiest to loosen the nuts holding the OPV on the top of both boilers. It gives you a little more room to manipulate your wrench. Then loosen the and remove the sensor. The factory seal involves a brass washer between the sensor collar and the top of the boiler. It makes it really difficult to get the dang thing off. I found my boiler was actually flexing at it's base and it was scaring me. I use a small tire hook (yeah, like, from the auto industry) to wedge between the boiler and the front of the machine in order to stop that flexing, and it gave me enough resistance to get the sensor off. On my reinstall, I used a small strip of teflon tape in order to get a good seal at the sensor threads, and they've subsequently been much easier to deal with.


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## Combercoffee (Feb 12, 2011)

Sorry I also haven't looked on this thread for a while emradguy but thank you for your reply/advice. Since posting the temp probe seemed to recover and began working again until a couple of weeks ago.

Both it and the release valve on the steam boiler failed. I have managed to replace both of them - you aren't half right when you explained how much force was needed to move the nuts! I nearly gave up but ended up with a wooden spoon wedge behind the boiler to stop it moving.

Advice to anyone who is thinking of replacing parts themselves is have a go. I'm not overly technically minded and with a bit of trail and error I have managed it and feel confident enough now to try any repairs (within reason!)

Thanks again to all who posted advice.


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## BloodyMezzo (Jul 14, 2015)

Gah! My machine displayed A2 this morning. Alex Duetto mk2, 4,5 years old from Stoll Espresso, Germany. I bought the extra warranty (5 years) as my former Isomac were just problems stacked on other problems and malfunctions.

I guess I'll start by sending them an email asking for a new sensor probe. Are the cables included, if it's not the actual probe that is faulty?


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## BloodyMezzo (Jul 14, 2015)

Got this from Marko at Stoll Espresso. Apparently the two boiler temp sensors are identical? I'd like to try this. The only thing that concerns me is weither the steam boiler will leak when I assemble it again. I thought the copper seals were one use only?

"Hi Björn,

yes, we can try to arrange it with warranty program.

In first step, you have to change the temperature sensor, sometimes the PID is also defect.

If you like, you can change the sensor's of the boiler's (but switch also the connector's), than you can use the espresso boiler.

If the PID works well, you must get than an A4 failure. Than switch of the hot water boiler by switch. * *

You want to try this? Than we know about the PID.

Please send me a respond than I can send you the part('s)"


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## BloodyMezzo (Jul 14, 2015)

I think my machine has overheated during the hours it was running before I noticed the A2. Some plastic details (the GICAR box and some plastic cable stripes) look like they've been under heat for a while. I ran a test and stood by the machine as it heated up. It wouldn't stop, when I used the lever there were water steam coming out of the group head. I flushed water for a while to cool it off somewhat and I noticed traces of something white in the water coming out. It seemed very soft in consistency, maybe like something that just had melted off somewhere. Unfortunately I didn't take a picture. When I ran water from the group today with the boiler cold the water looks clear.


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## BloodyMezzo (Jul 14, 2015)

My first thought was that it could be pieces of the white Teflon tape used to seal the connection to the pump. If the machine would be very hot for a while I guess the heat would spread through the metal?


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## BloodyMezzo (Jul 14, 2015)

Update: I switched place on the two temp sensors and I'm now enjoying great coffee again. No milk though until the replacement sensor arrives.


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