I have a very old GS/3 that has had most of the recommended upgrades. One day a few weeks ago, the reported coffee temperature started jumping around randomly every second. 170, 235, 203, 185, 307,... I cycled power by the back switch and it went back to normal. For the past few days, I'm greeted every morning (it turns itself off at 2pm and wakes up at 5am) by a machine at its regular set temperature, but an error message:

T.ProbeUnconnect
Cof.Boiler temp.

Again, cycling power makes the message go away and the machine functions perfectly for the rest of the day. Before I start randomly wiggling wires, does anyone have experience with this? Is it simple? A harbinger of expensive electronics replacement? Gotta do more tests?

Thank you,

Matt

I don't have experience with this error but I would take off the left panel and check the pid wire for the coffee boiler. It is the black wire with a lot of extra length coiled neatly next to the coffee boiler.
When I first got my machine due to several problems I opened the brain box and found a couple of slightly loose connections there.
But I would start with a simple check of the above mentioned wire.

Thanks. I've pushed some wires around. We'll see if it helps.

Matt

IIRC the pid cable screws on. But I have not looked at mine for a long time.
I'm sure others will chime in.

Turn off and unplug your machine immediately.

The error message you report is one that I and others have seen when there has been water incursion into the brain box that has contaminated the logic board. If this is the case, and you continue to run the machine, the logic board could be permanently damaged and, yes, that's an expensive part to replace.

Now, that said, It's possible that the error message is due to a bad temperature probe or connection. But you don't want to assume that's the case. You need to make absolutely sure that there aren't any leaks inside the machine.

Remove the side and top covers and carefully inspect the machine for any signs of leakage. Look on the floor of the chassis, especially towards the rear of the machine, and around the triangular plates on both ends of the steam boiler (if you see any signs of water around the plates, the gaskets are leaking.)

Another potential source of water is the vacuum breaker valve being stuck open due to contamination of the valve seat. You mentioned that your machine has most of the updates. Does it have the new vacuum breaker valve that routes steam/water into the drain box?

If you see any sign of water, it's a good bet that some has gotten into the brain box. This may have happened even if you don't see signs of water. If you're comfortable working inside the machine and with electrical circuits and such, pull the brain box out and remove the cover. Take a photo of the board to record the connections then disconnect the wires and remove the logic board. Usually the water collects in the bottom of the box and contaminates the bottom of the board, though it can happen to the top of the board as well.

Blot up any water you find in the brain box or on the board. Carefully check the board for contamination around traces and solder joints. You may be able to remove them with alcohol and a Q-tip. You can dry the board with a hair dryer, but keep the dryer far enough away to avoid overheating the board. It may help to store it overnight in a plastic bag with a handful of rice.

If you found water, do not put the board back in until you have found and fixed the leak.

OK! Thanks. I do have the new vacuum breaker.
I'll report back.

Let me guess. This is not good:

Board looked ok. Certainly no moisture. And best of all, nothing misbehaved when I reattached all the wires and tried a quick power test. I'll drain the boiler, put new thread compound on whatever that nut is that's leaking, and try again.

Thanks again!,

Matt

Cleaned the threads, and nut, wrapped everything in teflon tape, reassembled, no hissing at full temp + pressure, made a cappa. Here's hoping!

Thanks again, Dick!

--Matt

Excellent.

High probability that the bad fitting was the cause of the water incursion. The fitting is very close to a cable bundle that goes into the brain box. It's easy for water to wick along those wires and get into the box. That's why attempting to seal the opening in the box where the cables enter doesn't work.

Apparently only a small amount of water reached the board. If the water bridged some pins or traces it could have caused a short. There's usually enough mineral content to do that. But if it's working now there may not have been enough minerals left behind after evaporation to keep the pins or traces shorted. You'd have to look very carefully to see evidence of any contamination.

Watch the display carefully. Any unusual behavior likely means you need to clean the board. If that happens, be sure to shutdown immediately. We've heard from quite a few owners who had water incursion but caught it quickly enough to for the board to recover after drying and cleaning. I waited too long, running tests to see if I could figure out what was happening. Lost the board and had to replace it.

Also make sure the clock is working. Loss of the RTC chip or a short between the backup battery and chip are symptoms we've seen after water incursion.

LM now drills holes in the bottom of the brain box under the logic board. I believe it's a recommended mod. I'm not convinced it prevents water damage in all cases, but it can't hurt.

The clock works, but for the past few years, the time has needed resetting if the machine was turned off from the back switch or unplugged for more than a few minutes. All other settings are retained. I'll keep my eye on it.

--Matt