Silly little ice maker repair

[slashdev]

Long time lurker, first time poster...  This barely qualifies as "electronics", but it was a nice break from some of my "real" projects.  Ok, you might think it's silly to try and fix an ice maker in a 1990 freezer, but I wasn't ready to shell out $80 for a whole new unit.  Besides, I have the knack!    And by "knack", I mean I can fail with the best of them...

The TL;DR version: give your cam a wedgie.

The TL version:  After the wife threatened to call an appliance repair man, I finally took a look at the ice maker.  I cracked open the case and poked around a bit.  Then I reassembled it and... it made a batch of ice.

Apparently I had performed one of my favorite maneuvers: "Blowing out the baffling."  It's a technique I first learned on a cantankerous lawn mower: disassemble device, reassemble device, device acts like nothing was ever wrong.

But the ice maker quit working after one batch.     I checked the solenoid-operated valve, and the gasket was deteriorating.  Having replaced the valve once before, I just ordered a replacement for what I *assumed* was a marginally-operative valve.  We have an old house, and it's common for scale to work its way into valves and aerators.

I replaced the valve, buttoned things up, and voila, the wife is enjoying the Miracle of Ice once again.  Appliance Repairman avoided!

Or so I thought.  One week later, it stops again.  This time, the discharge fingers stalled after touching the ice.  Hmmm... I guess I really need to understand how this device works. I always wondered how those plastic fingers broke the ice out of the mold.

This may be old news to everyone, but the process goes something like this, starting with an empty mold:
1) Activate solenoid, which opens valve and fills mold
2) Wait until they're frozen.  There's a thermostat that closes when it gets below 17F.
3) Turn on the mold heating element.  This melts the ice away from the mold, making it very easy for the fingers to push the ice out of the mold.  When the thermostat opens around 33F, the motor begins turning the fingers.
4) After the fingers rotate back around and discharge the ice, the process begins again.

So maybe the heating element didn't free the ice, and the fingers stopped.  Everything ohmed out ok, though.  I took a closer look at the control cam:





WRT this photo, the cam rotates CCW and the 4 wipers are stationary.  The outer-most track had a lot of black sputter after the end of the track.  I cleaned that up, wondering if the char was keeping the wiper from making good contact.  The wipers looked pretty good:



I decided I could insert an isolation relay, thus moving all the arcing to the relay contacts (0.6A valve with 2A surge), and the wiper would only have to drive the 120VAC coil (about 10mA).

To house the relay socket and wiring, I ripped out the guts of a dimmer:









I also scratched the circuit into back of the enclosure and wiped it with some white paint:



There's plenty of room near the valve, but the valve is operated by a Neutral wire (white) and a Valve wire (brown) that the wiper connects to Line (black).  I needed an unswitched Line for the relay COMmon contacts, so I forked a spade connector in the junction box:





Then I nestled it in there and had the wife throw the switch: fingers rotate, valve opens, neon glows, ice freezes, ice discharges, fingers stop too soon... wait, what?



Fine.  Open cover, jiggle cam, fingers start moving. What the?  Remove cam and see fresh signs of arcing, but now they're on other tracks.  What is going on?

I put the cam back on, and the process starts fine.  I think I hear a little buzzing, though.  Then the valve opens.  And stutters a few times.  Huh?!?  How could a 10mA coil be stuttering from *clean* wipers?

I finally noticed that the cam is walking up off the shaft.     Eventually, the wipers quit making contact and we have arcing.  DOH!

I remembered taking it apart the first time I serviced it, about ten years ago.  There were two springy fingers on the shaft that latched when the cam was fully seated, and I had squeezed them together and broken off one of the fingers.  (See photo of wipers: right finger is missing.)  Ten years later, the remaining finger was no longer latching.  I grabbed a brad nail, roughed up the shank a little, and wedged it in the slot.  It works a lot better now that the cam is securely latched:



Yeah, coulda saved myself a buncha time: just wedge a brad in there, why dontcha?  Barkeep, I need a drink.  On the rocks.

Cheers,
/dev

[CrabxCore]

Looks like a fun project haha

I really enjoy looking at these type of timing circuits. So simple yet so complex.

[Rachie5272]

Wow, I have the exact same ice maker, with the exact same problem.  The same little finger broke off, was fine for years, then started acting up.  The mechanism is terribly finicky, but I managed to fix it by forcing a screw next to the finger to hold it in place.

Thanks for the information.

[ConKbot]

I think I've fixed the same kind of ice maker too. Cleaning some contacts, and epoxying the wheel back on because it was lose.

[tautech]

Welcome to the forum /dev.
Nice first post, well done.

Sure to help others with similar problems.