Help Diagnosing Brew Control Electrical Problem?

[Java Man]

I need help diagnosing an intermittent control problem with my auto HX machine. Perhaps someone can review this and suggest ways to narrow the potential causes?

The machine is a 2004 Wega Lyra/mininova. The main control board on this machine is a Gicar, and the brew flow control is a programmable flow Giemme unit.

Emergence of Problem
The machine operated flawlessly until a few weeks ago, when the troubles began.

I first noticed a problem when activating the brew switch began causing the brew solenoid to click, but would not start the pump or open the brew solenoid.

I replaced the brew solenoid and valve with new parts. When I first restarted the machine after this replacement, it malfunctioned for the first 10 shots or so, then began working normally. This eliminated the problem for a few weeks, and I thought everything was fine. But now the problem is coming back intermittently.

I'll describe the behaviour and perhaps someone can suggest a way to narrow the list of possibilities.

Hot Water Control System
This machine has a dedicated switch and solenoid to activate the hot water tap. No matter what has happened with the brew control circuits, the hot water control continues to operate normally. Turning it on engages the pump and produces hot water with no interruptions, regardless of what is happening with the brew control. I think this eliminates the pump and pump circuit problems from the list of possible causes, and narrows the potential problems to the brew control system.

Brew Control System
Sometimes, the brew control system works properly.

Other times, turning on the brew switch starts the pump for several seconds, but it shuts off spontaneously part way through the shot. When this happens, it has been possible to restart it immediately to finish the shot.

Still other times, turning on the brew switch has resulted in a click in the Gicar control unit and a simultaneous clunk in the brew solenoid. But it spontaneously shuts off within a fraction of a second. When this happens, the Gicar controller sometimes begins clicking continuously, stopping only when the main power to the machine is turned off. This seems to be identical to the problem I experienced before replacing the brew solenoid and valve.

Automatic Brew Flow Controller
This machine is an auto with programmable flow control managed by a Giemme flow control unit. Disconnecting power to the Giemme flow control unit does not affect the errant behaviour of the machine.

Brew Control Touchpad
The brew switch and brew programming control is a 4 position touchpad connected to the Gicar control box by a ribbon connector. See parts 11 and 13 on this diagram:

http://www.espressoparts.com/cate...electrical_system/

I don't know how to diagnose a problem with the touchpad. Is it likely that this is the problem?

I can order a new Gicar control unit (it's $483!!) but I don't want to do so until I can confirm it is the problem. I certainly don't want to order and install a new Gicar control unit only to discover that it isn't the problem, and then I can't return it because it's used.

Any suggestions?

[cafeIKE]

The first thing to look for when heat, moisture and electricity are mixed is corrosion.

If you haven't thoroughly inspected EVERY crimp and connector, now's the time.

Plastic membranes are usually very reliable, often with the plastic splitting long before the switch fails.

HTH.

[gosuzuki]

I had a kind of similar problem on FAEMA Due A-2. The problem was the amount of hot water was not certain, and touch button started to malfunctioning one by one. The cause of this problem was defect since manufacturing, connection between ribbon cord and plastic connector. I figured that it was functioning at first, but because of the heat, connector distorted a little and made a short between lines. This caused all kind of malfunction on control unit. After fixing this problem, everything worked just fine. Of course I had to re program brew seconds on every button.
I suggest checking every line of touchpad through control unit.

[Java Man]

Thanks for your suggestions.

I've checked through the electrical connections in the machine and found no problems.

I've also traced through some of the circuits with a meter to check continuity. Again, no problems.

I've also disconnected components one at a time to see if they affect the machine's behaviour. For example, disconnecting the boiler inlet solenoid doesn't fix the problem, nor does disconnecting the ribbon connector from the brew control pad/programmer to the Gicar controller.

This was the problem that prompted me to replace the boiler inlet solenoid and valve several weeks ago. (Even at that time, I thought it might be a blown Gicar, but at $483 for a new one, I opted to replace a $77 boiler inlet solenoid and valve instead hoping that was the problem.)

Initially, replacing the boiler inlet solenoid/valve eliminated the problem for a couple of weeks. But it began malfunctioning intermittently, and now it is malfunctioning consistently, just as before. I think it's unlikely that the new solenoid and valve are causing exactly the same problem as the original parts did.

The machine is now malfunctioning consistently as described in previous posts -- no more "OK" periods.
Turning on the main power switch causes a relay on the Gicar circuit board to click every second or so. It arcs and clicks, but doesn't stay closed. The relay appears to be for switching power to the heating element because the machine doesn't heat up, but the pump operates normally.

I checked the impedence of the heating element and it's 1.3 ohms. I don't know whether that's right, but in any case, disconnecting the power leads to the heating element doesn't stop the relay on the Gicar from malfunctioning. So it's probably not the heating element, either.

For the first year I owned this machine, I turned it on an off every day via an appliance timer. After a year or so, Terry Z (EPNW -- Wega retailer) cautioned me that operating these machines on a timer seems to bring on control board failures.

I'm stumped. I think it's time to bite the bullet and to order a replacement Gicar control unit.

Java

[jggall01]

Can you replace the relay on the Gicar?

The 1.3 ohm reading sounds very low to me. Assuming 115VAC, this would seemingly draw around 90A

Jim

[Java Man]

I've read that the impedance of heating elements is very low . . . but 1.3 ohms seems very low to me, too.

I can't see how the relay on the Gicar circuit board is fastened. The terminals connecting it to the circuit board are soldered in place from the back side of the board. It suppose I could see if a similar relay is available. I'll see if I can get a decent photo to post.

Rick

[cafeIKE]

Since the relay is toggling, the drive circuit may be at fault.

Or there could be a current sense that disengages the relay if too much / little current is flowing into the heater.

First thing to determine is the DC room temperature resistance of a known good heating element. IIRC, NiChrome resistance about doubles between room temperature and boiler temp. Assuming ~1.2kw @ 120v = ~10A = 12ohms, cold DC resistance should be about 6ohms

[Java Man]

Googling for the relay yields only one hit -- in Chinese. The identifier on the side of the relay is JQX-14FW/Q18-HS. It appears that it's not available through retail channels. I think it would be difficult to buy just one.

The resistance of the heating element, though, doesn't seem right. I get infinite impedance between either terminal and ground, but minimal (~1 ohm) between the terminals on the element. I wonder if the heating element is defective, and is causing the relay to malfunction? I think I'll pull the element to check it out. If it's really only ~ 1 ohm, it needs to be replaced anyway.

Thanks,

Rick

[ntwkgestapo]

The element MAY be internally shorted "to itself", i.e. a significant part of the coil of Nichrome wire (inside the outer shell) may have collapsed in upon itself, shorting out a large part of the wire. As an example of what it SHOULD be, my Gaggia Factory has a 1000 watt heating element and operates @ 120 volts (ideally). This results in the resistance of the element (by calculation) being 14.4 ohms. A larger wattage element would have less resistance at the same voltage as it would "dissipate" more power. AN example.... 1500 watt element, 120 volts = 9.6 ohms. You can calculate what you SHOULD have (this would be an ideal resistance) by first dividing the wattage (the 1000 watts or 1500 watts or whatever) by the rated voltage (120 volts typical in the US, 220 volts typical in Europe) THEN dividing the rated voltage by the results of the first equation. Watts/Volts=Amperes. Volts/Amperes=Resistance (in ohms). That would give you a "target" resistance. I say "target" as there WILL be variations from the ideal. The 14.4 ohms for my Gaggia ACTUALLY measures 13.9 ohms (but the meter I'm using is NOT a calibrated device, so the displayed measurement could easily be off)..


Hope I haven't bored you , but, there's some info to work with!

[Java Man]

Bored, Moi? Not at all! And I think you're onto something.

I pulled the heating element and tested the resistance. Now that I can easily reach the terminals with the probes from my multimeter, I get resistance of 0.000 ohms. I'd say that's low enough to be a short, wouldn't you?

It's possible that the functions built into the Gicar controller include short-circuit detection to avoid overheating the relay in the event of a short in the heating element, so maybe replacing the heating element will solve the problem? We'll see. Strangely enough, there have never been any indications that the heating element wasn't 100%.

Here's photographic evidence of how soft the water is in Vancouver. This machine has never been descaled, and has been operated daily for 3 years, 11 months.



Cheers,

Rick

[ntwkgestapo]

I WISH my water even APPROACHED that soft! Where I live it's all pretty much subsurface water from limestone.... when it's SOFT it's HARD! I descale my Gaggia about once every 6 weeks just to keep the lime/calcium scale under control!

[Java Man]

More developments:

Although my multimeter has a 0-200 ohms scale, the manual recommends using the 0-200 ohms setting only for continuity testing, and not for measuring resistance. My heating element measures only 0.5 ohms on that scale, but my kettle measures 0.4 ohms and my iron 0.6 ohms. So the low reading on the boiler element has been due to a misleading measurement (and operator error!) rather than a faulty heating element.

I reassembled the machine with the old heating element, but connected my iron to the heating element leads to provide a proven load of known amperage. The Gicar controller functioned normally. So I reconnected the heating element, and wouldn't you know it -- the machine is once again working normally. This happened the last time I re-assembled it after several days sitting apart on the bench. I'd bet it's only a matter of time before it malfunctions again. I suspect the Gicar is wonky and will emerge as the problem. Let's see what tomorrow brings.

Rick

[automatic74]

your element is a red herring mate. and i think you are using an insulation meter(megger) to test resistance iron etc = 20ohm approx min. you guys didnt mention if safety pressure switch was fitted in brew controls? if intermittently faulty, a week/damaged spring would give signal back to cntl card to switch of pump well before any pressure/flow has had time to build up. this might explain output card clickin on/off/on etc ie start, pump on/solenoid open, pressure rises, faulty PS switches, pump stops, pressure drops, faulty PS switches, pump on etc etc all happening very quickly. also look at flow switches if any. do you have problems with product causing blockages? sticky?? your machine likes to play after some rest possible water ingress on to press/flow switches then drains of over night/days i would be lookin at those input devices guys

[Java Man]

A new Gicar controller arrived from Italy yesterday. Before installing it, I tried running the machine with the old one, and it continued to malfunction. I then replaced the old Gicar with the new one. A day later, the machine is still working flawlessly.

Automatic, thanks for the ideas. The safety pressure switch on this machine is purely mechanical and has no electrical connections.

Rick

[automatic74]

thats good news. glad you got to the bottom of that fault. i will look out for your posts to see if it worked. I hope you let me know if not over time. ps if pressureSW has no elec cons it is a pressure relief valve with a spring and can cause problems with control card check it out !!!!!

[automatic74]

any other problems coffee makers???

[Java Man]

thats good news. glad you got to the bottom of that fault. i will look out for your posts to see if it worked. I hope you let me know if not over time. ps if pressureSW has no elec cons it is a pressure relief valve with a spring and can cause problems with control card check it out !!!!!

Thanks for the offer, Jason. I'll post of there are further problems.

How can the pressure relief valve cause control card problems?

Thanks,

Rick