Thermal fuse burns again and again

Hi!

>I have replaced the lower thermal fuse on the steam generator of my EAM 3500 S Pronto Capppucciono 3 times in the last weeks. I thought this was the reason for the lack of steam. Hot water didn't work either. But obviously the blowing of the thermal fuse is only a symptom of another error...

My machine is already old. Except for the grinder, I have probably already replaced all parts at least 1x, including the control board. That was a long time ago. But I replaced the steam generator only a few months ago.

What can be the cause, what can I do?

A triac sits on the cooling body on the power circuit board. He is responsible for the control of the current for the heaters. In most cases it works again, if this is changed. Or a spare board.

HWS

Ok, since I am not the noble solderer, I ordered a completely new power board. Also on suspicion the temperature sensor, which sits on the steam generator and of course a new thermal fuse. I received the delivery today and installed it right away (yes, also using thermal conductive paste).

The machine now runs again and makes steam again, thus foaming milk again. But she did that again before, when I had only replaced the defective thermal fuse on the steam generator. Which I've done three times before. The last thing that never worked, however, was the supply of hot water. Here only a few drops came, before the cover broke off...

Now, even now the cover of hot water still does not work! Which fuels the suspicion, the circuit board / the triac was not defective at all!? - So maybe in a few days the thermal fuse will blow again, and I am as smart as before?!

Any ideas what the problem might be with hot water? In principle, you should be able to make a cup of hot water for a cup of tea, shouldn't you?

The joy was short-lived. Yesterday evening a trial cappuccino after installing the new parts, then another 2, 3 cups for breakfast. Only then did the steam go insufficiently. Now nothing works anymore: After switching on the machine heats up forever and then reports: "General fault". So I can't even make coffee anymore. Not to speak of milk foams...

Bin helpless.

Help!!

I've looked again now. As suspected, the lower thermal fuse of the steam generator has blown again. I bridged them by connecting the two connectors with a piece of wire. Shouldn't be too big a problem?! After all, there are two thermal fuses on the steam generator. Anyway, at least that's how coffee comes in again. Steam only comes a little. This is not enough for foaming milk.

Also: Despite exchanging the power board, the temperature sensor and also the rear soleonide valve, the lower fuse of the steam generator burns through again and again!

Maybe it is the steam generator itself?!

Do you really mean thermo fuse or thermostat?
And if you mean the thermostat, did you take one with 318°?

I have an exploded view of the machine from the net where the part is called "overtemperature protection". But you're probably right: When it was ordered, it was marked as "DeLonghi Thermostat for Steam Heating 318°C". That makes sense. If it was just a fuse, then the steam should work again if you bypass it...

Also: I replaced the lower thermostat (318°). Several times now. Whenever I have it freshly installed, there are a few cups of cappuccino with foamed milk. But hot water doesn't work. Then the vapour pressure seems to weaken. There is still a little steam, but it is no longer sufficient to suck up the milk. Finally the thermostat burns out, the machine then reports some time after switching on only "General fault". If I bypass the defective thermostat, there is still no foamed milk, but at least coffee.

Why I suspect "Triac defective" I have already installed a new power board. No effect. A newly installed thermostat quickly burned through again... :-(

On the net I find a few cases of the same kind. Unfortunately always without a hint to the solution of the problem...

Bin thankful for every tip! What can I do?

Have you ever replaced the temperature sensor?

Yes, I did! As mentioned in a previous posting:

Schlawi: The part is called a thermostat, but it is an overtemperature fuse!
If it were a thermostat, then after cooling the contact would close again, but it does not. Once the overtemperature fuse has triggered, it must be replaced.

@immado: Since you reported that the hot water and steam supply is only very weak, you should check whether something has become clogged with lime at another point. Either the front solenoid valve or a pressure hose line.
If not enough water flows in the steam heater, the heat will not be evenly distributed in the radiator. Before the temperature sensor detects an overheating at the upper end, the lower overheating protection has already been triggered.
All clear?

Thank you Steinhaeger, this explanation makes sense!

I have now also identified the culprit. For this purpose, the hose connections were disconnected one after the other in order to see whether water still arrives at the relevant point when hot water is supplied. It's the rear Soleonide valve! When hot water is drawn, water only comes through at the beginning, but it quickly turns into a trickle, after all only a few drops come out.

And I also bridged the rear Soleonide valve, so I connected the thermoblock directly to the steam generator. (I had once replaced all the hoses and used one of the old ones for this). And already there was both hot water and steam!

Seltsam only: I had recently replaced the rear valve! I had read of a similar case where multiple switching of the valve in test mode had solved the steam problem. That worked for me too at first. But then not anymore, which is why I replaced the valve...

I removed the valve and screwed it apart and put it into a strong descaler solution, although there are no visible deposits. Maybe it helps?!

Otherwise I can order another new valve and a new thermal fuse and install and see what happens...

Comments welcome!

Hello inmado,

That's strange with the valve...
Had you replaced the valve or replaced the solenoid? Has the solenoid also been replaced?
Do you have a high degree of water hardness?
The disassembling and in descaling solution put is already a good idea, I would work on the small channels in the housing also still with a small brush and descaling solution.
If you did not change the solenoid coil, you could still do this.

After I have reinstalled the cleaned rear soleonide valve, both hot water and steam covers work. Correspondingly there is now foamed milk again! (Let's see how long...?!) Any deposits were visible but not!

magnet coil?

Yes, the small square part with the connections for the power lines is a magnetic coil.

Oh, I see. But the solenoid coil is part of the soleonide valve and that only exists as a whole. Since my machine works now 2 days without problems, I will now order the thermal fuse (currently I have it still bridged) and in addition still the rear Soleonidventil "on stock". The things are from my point of view anyway "wearing parts"...

Many thanks for the support!