HEATING UP PLEASE WAIT – SOLVED

This is a problem I’ve dealt with in the past and in fact found a different solution to it. But it’s important to log this solution as I get calls and emails pertaining to it. I have noted it usually occurs on the old Primadonna’s. Great machines I know but some of them are fifteen years old now and really can be a pain in the arse to repair, especially milk flow issues and this issue.

So what is this issue. The issue is the machine boots up ok, lets you make coffee ok but presents a stubborn annoying flag on the screen “waiting for heating” usually when you attempting to make a hot water or a milk selection. You push the button and the waiting for heating flag comes up and you push its again and it waits again. Eventually the machine does respond and runs the hot water or runs the steam, usually. Sometimes it will default to the general alarm, usually after its been left idle. Testing of the elements show they are ok and getting voltage. So what’s going on?

Keep in mind that I said I have found other solutions to this issue in the past. So I’m being specific to this machine. I will now eliminate the things that have solved the issue in the past but did not work this time. Also keep in mind, I do not have access to any technical data from Delonghi. I only have what I can find on the internet like you. So I guess a lot, I’m not kind of authority on these machines. I’m just reporting how I eventually solved the issue by guessing.

  1. The switches on the front that detect the water spout or milk jug. These switches carry high voltages (I don’t have a schematic and have not taken the time to measure voltages, I am assuming all of this) and when activated close the circuit to energise the Flash Boiler (again don’t quote me), so what you say. Well I don’t know why, the flash boiler does pre-heat the hot water (again a guess) but it obviously flashes the water for the steam. So when these switches get covered in milk and stuff they offer resistance or don’t mechanically activate (again conjecture) and this waiting for heating error can result(personal observation). This time I changed them and the issue persisted.
  2. The Triacs, we have had a case where a Triac was outputting a half sine wave, (acting a bit like a light dimmer) to the flash boiler, so half voltage and the element failed to heat as it should and caused this issue. I changed the board this time and the issue persisted, this time in Italian.
  3. The NTC sensor. Most people get this answer from a forum or a freindly Delonghi Technician and then they buy a sensor cheap off ebay. They fit it and the issue still persists. They have already annoyed the real Delonghi guy, so then pretend they purchased it from me and phone up ask why it did not resolve this issue. The answers obvious, they didn’t buy it from me. Sometimes replacing the sensor or putting new heat paste on the sensor can solve this issue, but not this time.
The switches on the front, ensure they are clean and the connections secure.

So here is where I was out of ideas, but then I really thought about it, at 3am. The General Alarm was coming up after the machine had been running for an hour and was nice and hot. So at some stage the processor got the message that a boiler needed heating, applied the voltage and the sensor failed to tell the processor that the element had reached the target temp within the allocated time. And thus the processor flagged the general alarm. This sounds like a HIGH RESISTANCE CONNECTION in a hot place. Or otherwise stated, a loose connector on an element. As the element gets hotter, things expand and suddenly we have an increasing air gap between the element connector and the spade connector and thus no voltage. No voltage = no heat But you are saying ‘you tested the voltage right at the beginning’, yes I did but the machine was cold.

Now I like this theory but it was only half correct. I tested all of my connecters and they were ok. I re-crimped them just to be sure. The issue persisted. What the hell is it then, the elements themselves? Then somehow I made the leap, what about a faulty fuse. Oh and bloody finally some luck. I tested the flash boiler thermal fuse/thermost when the element was hot and it was very high resistance. I pulled it off and let cool and the buggar was normal. These fuses or thermostats depending on who you ask,( I can’t find a data sheet) are meant to protect the flash boiler in the event of a major thermal failure and I believe function as a fuse. They should go open circuit at 318 degrees, not before. But this one was acting as a thermostat. Which is what they are I think but its obviously acting as a high resistance connection and when hot (measured at about 70C), going completely open circuit.

So I shorted out the thermal fuse/thermostst and all the issues were gone. I could run off hot waters at a rapid rate and only every now and again got politely asked to wait, just long enough to scratch my nose between hot waters. The issue was solved.

Ive shorted out the Delonghi Thermostat with another fuse and removed it off the Flash Boiler. Don’t try this at home.

In conclusion the cause was obvious. But it always is in hind sight. It’s just that I don’t know how these thermostats or fuses are meant to function. I thinks its obvious they vary their resistance with heat to some degree but up until now I had assumed they only failed by getting stuck in open circuit, but I now know they can vary their resistance erratically. The fact is they are very sly and I’ll always put them at the top of the suspect list from now on. I’ll try and post a data sheet for them.

Leave a Reply

%d bloggers like this: