OK guys, I need some help getting our Giotto back in action again. Yesterday the safety valve popped and released boiler pressure; pressure gauge read 2 bar; and the heating element was still on. I turned it off immediately, and have not turned it on since. As my knowledge of the inner workings of the machine are somewhat limited, I thought I'd check in here for some advice.

I'm surmising that the pressure switch is faulty. Am I on the right track here? Is there a way to test the pressure switch? Could there be any other cause of this problem? Electrical fault? Loose or corroded wire?

I should also mention that the machine was idle at the time of the overpressure. There was no shot being pulled, steaming, or hot water being drawn. It had been idle for several hours, with no activity of any kind.

At this point, I have not opened up the machine to have a look, pending some feedback and helpful pointers from here. Thanks in advance....

Svend

The diaphragm on pressurestats will stiffen and can scale over time. They will all eventually fail which is what it sounds like you have. You can take the pressurestat off, put a little vinegar in it and let it soak for a while, then rinse it out to see if that fixes it. Sometimes simply tapping on top of it will un-stick it but if it happens again, you would be best to clean it or replace it. The are relatively inexpensive.

Search on "sticky pressurestat" for similar reports and suggestions.

Applying a little vinegar to the pressurestat "opening" using a simple plastic syringe is a great idea. Let it soak for an hour and then rinse with the plastic syringe and plain water.

If this does not cure the problem, the fault MAY lie with one of the relays on the Gicar board, specifically the one labeled for high current (16 amps). The pstat controls this relay and the relay closes the circuit to send power to the heating element. I can provide additional troubleshooting tips but lets try the vinegar first. Get your camera out and take some pics of the machine's innards and post same.

Thanks! This place is the best! I'll try that tomorrow and post back with what happens.

Quick question: when I take the Pstat off, what should I use to reseal the joint? Teflon tape?

SNielsen wrote:Teflon tape?

Yes.

So, here's the latest.....(problem still not resolved)....

I took the Pstat off from the top of the coil tube, and found that the tube was full of water right to the top. Is this a normal condition? Is the water level in the tube too high? BTW, no water leaked out when the Pstat came off, and the unit was dry, so no water made it up into the stat itself.

I soaked the stat in vinegar, as suggested, rinsed and re-installed. Reassembled the machine (leaving the side panel off), and turned on. Instead of the boiler filling and heating, there was a continuous clicking from the Gicar box, like a relay clicking on and off, freq about twice every second. This is the same condition that I posted a query about a couple of months ago (see here: Giotto clicking at startup) The clicking problem never got resolved, BTW, as I've had no time to look at it -- way too much travel; out of town almost constantly since April. So we just left the machine on 24/7 and thus avoided the startup clicking problem.

In any case, with this relay problem, the machine won't fill the boiler, nor will it heat. So bottom line is, with the machine not heating, I still don't know if the Pstat problem is solved. And now I have to fix the dang relay first.....

OK, regarding the relay now......I did as suggested in the previous thread, and pulled the water level probe out of the boiler today while the stat was getting it's vinegar soak spa treatment. The probe was pretty clean, but I polished it all up nice and shiny with some emery cloth. When the clicking started, I tried grounding the probe lead, but this had no effect....the clicking just continued as before. Unless you guys have another suggestion, it seems to me that the relay is funky and needs to be replaced. I looked inside the Gicar box, and everything is soldered to the circuit boards. Does this mean I need a whole new Gicar? Or can I get a new relay only, and just solder the new one onto the board?

Cheers, and thanks...!

Svend

relay? i dont think the giotto has one.
similar probs on mine pointed to a failing gicar controller.

I do hope that it is a sensor problem and NOT a Gicar board problem but that is one of the reasons I said this, previously:

Get your camera out and take some pics of the machine's innards and post same.

Pics of the pstat, Gicar wiring diagram, small reservoir where the OPV hose leads to, etc., etc. would be helpful as it can be difficult (and maybe misleading) to troubleshoot a problem over the net. The Gicar board in a Giotto is TYPICALLY fitted with three relays. One receives a control signal from the pstat and, in turn, controls the machine's heating element. Another is the common double-pole, single-throw (DPST) for boiler fill that most similar machines have - this starts the pump and opens the fill solenoid when the boiler needs water. The third relay is controlled by a level sensor in the small "baby" reservoir which sits directly below the main water tank. I do believe it is this third relay which is doing the chattering upon start-up as it also shuts off power to the heating element and pump/fill solenoid when no water is sensed in the small reservoir. It is probable that the pump could still be operated manually by means of the brew lever.

The small reservoir should have a white(?) wire attached. TEMPORARILY attach this wire to a good chassis ground connection (parts from Radioshack) and see if the chattering goes away.

edit - 6/26 - my description of the relays above is incorrect. My statement that "One receives a control signal from the pstat and, in turn, controls the machine's heating element" is misleading. That high power relay is closed when the machine is turned on and the water level in the reservoir is satisfactory. Power goes through this relay and on to the pstat and safety thermostat before reaching the heating element.

Hi Eric! Took the day off for Father's Day, so no progress to report today. Will take some pics tomorrow and post back here. If you're a Dad, hope you had a good Father's Day too!

BTW, my Giotto does not have a mini-reservoir under the main water tank, and thus no sensor in there. I think the newer models have this, and in these the water is drawn from the bottom of the tank. I have an older machine which has hoses which drop into the tank from the top (I do have pics of that....see below). Low water is sensed by a two pairs of metal prongs which hang into the tank from the top edge. The outer edges of the frames from which the prongs hang, are short metal bars and are used to suspend the tank around the machine frame. One of these rests on a contact to which is attached a wire lead which is directly connected to the Gicar. The other side rests on the machine frame (ground). When the water level drops below the bottom of the prongs, the circuit is broken.

This is a pretty simple system, with no sensor to fail. Tomorrow I will check the contacts and ground to make sure it's all sound, as well as clean all the bars and prongs of scale and corrosion. Not sure if this could cause the relay to behave like that, but I will test and clean nevertheless.

(Note that in this pic the top edge of the tank shows the sensor bars sitting loose on the tank edge where the holes in the side of tank have broken. This is an older pic, and I have since redrilled the tank and remounted the bars to give proper contact)