On Friday, January 6, 2017 at 1:43:02 AM UTC-5, Jon Elson wrote:
We have a Kenmore 110.28082700 washing machine that I've done a lot of work
on over the years. These seem to be famous for getting an "LF" long-fill
error. Well, we started getting that again, and after a good deal of
fooling around and false starts, the problem came down to valves operating
at the wrong time. I STILL have no idea why, but I know what it isn't.

There's a pressure sensor used to detect water level. I took it off the
board and tested it, and it appears to work as desired. it has a part
number that doesn't match anything on Digi-Key, but it is clearly an NXM
sensor similar to a bunch of models Digi-Key does carry, and that was enough
to be able to power it and test it.

The design of the water valves is this: There is a hot and a cold inlet
valve, and a thermistor. Then, this goes to a manifold with 4 valves. It
can dispense directly into the basket, and this works fine at a fast flow..
Or, it can dispense into the detergent cup, the softener cup or the bleach
cup, to send those solutions into the wash. These run very slow, so as not
to overflow the cups.

So, what we see is the basket fills for a while with the direct valve, then
that shuts off, and it fills the rest of the required water level from the
detergent cup, ONLY. This takes so long (it can take up to 45 MINUTES!!)
that the machine stops with the LF error several times before it gets to the
washing stage. I can see why it turns on the detergent valve, to add the
detergent to the load, but I do NOT see why it shuts off the direct fill
valve. After trying many tests, replacing the relay for the direct fill
valve, etc. and not fixing it, I finally kludged it. I tied a wire from the
detergent valve to the direct valve so that when EITHER relay is turned on,
it will open both valves. I can't really see a downside to this hack, and
it seems to have solved the problem.

The controller board is $264, and has a VFD for the basket spin/agitate
motor, the pressure sensor and a whole raft of relays to control the two
pumps, 6 valves, heater and door lock. One other relay failed before, and I
replaced that with an SSR. So, I really don't want to replace the thing if
I don't have to. The only things I can come up with that could cause this
behavior a

1. defect in the microprocessor (seems unlikely)
2. defect in the relay driver chip (I'm guesing it is some
house-labeled Allegro chip) that causes it to shut down
the relay output after several minutes.
3. intermittent connection in the wiring to the valve
The relay has been replaced, and I now have accumulated 3 sets of the valve
manifold assembly trying to keep this machine working. So, it isn't a
defective solenoid coil or valve. (They all fail the same way.)

Anyway, the machine seems to be back working at a reasonable speed per load
without having to keep checking if it stopped.

Any comments?

Jon

If you're lucky. Most people aren't though. We were at Best buy shopping for a new refrigerator a few years ago. (Not my idea. My wife couldn't deal with the little bit of rust on the bottom of our 22 year old GE any more). So we donated it to the Boy Scouts and I bit the bullet. Anyway I had done some figuring too. I figured that the damn divorce would have cost me a hell of a lot more than a new refrigerator, so we bought the friggen thing. I mentioned to the sales manager that I was a TV repairman and I commented on the shoddy way things in general were built these days. He took me aside and told me straight out that when buying a major appliance it is now necessary to protect yourself with a service contract. Yes it's a ****ing ripoff and I hate paying it every year but we are now on our 4th LG. If I could only get my old GE back.... This is the new norm, and it sucks. And make no mistake, it is the way that dirt bag companies like LG stay in business. Lenny