This over temp problem with the BES-920 presents as a rumbling gurgling sound and then the machine goes over the set 93 degree temperature and switches off. It’s annoying as the occurrence of the fault becomes more frequent and interrupts coffee production at crucial times. Like first thing in the morning.

I have had a couple of BES 920 machines with this issue come into the shop and the usual solutions are not the right ones. As it is an interesting problem I’m gonna blog about it. Now if you have this issue occurring with your Breville BES 920, then you are definitely going to want to read this blog, unless you want to spend the weekend chasing your tail as I did. I will also reveal the secret code to entering the Bes-920 error logs and test functionality. This will be very useful for future diagnoses of your Breville BES 920 coffee machine. Did you hear that google?

Now I have a mate working for Breville who apparently knows all about these machines and their faults, actually he doesn’t and it’s his fault I wasted so much time on this issue as I believed him when he told me things. So trust me if you think my solution to this issue is a red hearing well so did he and he was wrong so trust me I know the answer, some Breville Techs do not.

Right the first stop with this issue is to enter ino the Breville BES-920 fault log and reveal what insights it tells you. See here for instructions on doing this. Now if I knew then what I know now I would have seen the answer to the problem right there in the log. It had 2 errors registered, error 8 (coffee flow error) which had occurred about 6 times and error 10 (Coffee NTC over temp). Which registered about 17 times.

These 2 errors were correlated but I did not know that. So I noted them down and reset the error logs. All this is mentioned in the link.

Now I had 3 theories:

1. The coffee boiler was over heating (seemed obvious).

2. However I noted that the machine would go over temp when not drawing any current. The element did not appear to be on. So this led to my second theory Hot water from the steam boiler was leaking into the heat exchanger. Remember in the BES 920 water goes through a pipe (heat exchanger) in the steam boiler and the steam boiler sits at over 130 degrees. So it could have been getting hot water from the steam boiler due to a leak sucking water/steam. Or the steam boiler was going widely over temp.

3. The BES 920 has 3 elements and 3 associated NTC sensors. The temperature displayed is actually calculated from readings from all 3 sensors, the coffee boiler, the steam boiler and the group head sensor. Perhaps the group heater (sits under the coffee boiler) was faulty and was running too hot leading to the coffee boiler over heating. Possible.

So my first action was to resolve the leaks. There were a few leaking orings that could have been causing movement of hotwater between the boilers. I fixed these and then went for the other obvious component, the Coffee Boiler NTC. It was not difficult to replace but achieved nothing.

testing breville ntc sensors

Ensuring the readings from the NTC sensors are accurate.

So I used my temperature tester probes on the steam and coffee boilers and then entered the Breville Bes-920 check mode to view the temperatures of the coffee boiler, group head and steam boiler as displayed by the machine. They should not be over 95 for the coffee boiler, 135 for the steam boiler , and 89 for the group head). See how to enter the Self check mode here. They correlated closely with what my probe was telling me. With the coffee showing about 100. So there did not appear to be any fault with the machines temperature sensing. I changed the group head NTC just to waste some more time.

So now I contacted my mate and told him the story. He assured me I had missed a triac locking on. I should be able to see the machine pulling more than 0.09 Amp with the switch off. I recored 0.07A but he said look for corrosion on the steam boiler where the heat exchanger exits, if this is corroded you have a triac over heating in the boiler. This sounded credible like he knew what he was on about and Triacs are very hard to test in circuit so I believed him and changed the Triac PCB. This is no easy task, so I was bloody pissed off when it went over temp again.

I spoke to him again and could tell he did not have a clue. He was telling me to look for leaks again. I was on my own. So I decided to put a transparent tube between the boilers so I could see which way the water was moving when the gurgling occurred as this always proceeded the temp alarm. I could clearly see it was the coffee boiler over heating and gurgling back toward the steam boiler.

This is when the penny started dropping as I noticed once when I turned it of and on it immediately filled the coffee boiler by running the coffee pump. So it clicked the software had just checked and found the coffee boiler not full to the high level probes, yet it was just heating that thing with the tide low. A lesser volume of water not covering the probe could cause the water to exceed boiling temp as the probe would not register true water temp as it was not saturated. Now the initial flow faults error 8’s registered and I went back and checked the faults and yes there were 2, the error 10 and a coffee flow error 8.

Now when I told my mate of course he knew all about this and told me some crap about draining the coffee boiler and measuring the volume if it was low then there was a flow error. Really you think. I did not do all this as the fault was intermittent I knew the pump or a valve was involved so I changed the pump and bypass valve. And the fault was gone.

So whats the moral of the story, when in doubt change the bloody pump. And in the case of a Breville the bypass valve on top of the pump as well. And don’t rely on someones else’s solutions for your coffee machine issues. They are bloody complicated and if you go off on a tangent hours gets wasted. So don’t assume anything. It could have been the triac leaking some current to the element but the fact that I was just not seeing a significant current draw during the gurgling should have steered me away from the Triac/NTC theory. You cant rely on your mates even if they work for Breville.

Longer tube to determine which direction hot water was moving between coffee and steam boilers.

Brevile coffee group NTC

Breville Triac Boards

Replacing the Triac PCB – Usually done when the machine pulls more than 0.09A with the switch off

Purchase Breville Coffee Machine Parts here….

Comments are closed.

    Your Cart
    Your cart is emptyReturn to Shop
    Independently verified
    1410 reviews