KSSS48QDW05 Defrost Timer not advancing in cooling mode.

[Jack UvAllTrades]

My Kitchenaid freezer won't go into defrost mode because there isn't power to the timer when in cooling mode (so it doesn't advance).
Background: The fridge was warm (maybe low 50s) and freezer was getting there (ice cream was very soft, but we still had ice cubes). The defrost timer was making a lot of noise/buzzing. I ordered a new timer and in the meantime defrosted the coils, which were completely frosted over, by manually advancing the timer and also by taking the cover panel off in the freezer and gently using a heat gun to help it along. The coil was also visibly red hot, so it is working fine. I put it back together, and the cold temps recovered pretty quickly.

The problem is that the new timer didn't fix the problem. The coils are still icing over every few days (we are in and out of the fridge a lot, but have been for 20 years, so that's not new). I gotten into the practice of manually advancing the timer a couple times a day or manually defrosting the coils if I forget. On the first click, it WILL go into defrost mode and the heating element does get hot and do its job. It will also advance on its own into cooling mode after it has defrosted, where the compressor kicks in and the fridge operates normally again. The problem is that the timer does not advance at all when in cooling mode. I tried another timer from a different fridge and had the same problem. It will sit in the same position until I manually advance it again to defrost.

The timers both have 7-8 K-ohms of resistance across terminals 1 (supply) and 3. The normally closed terminal 1 and terminal 4 contacts (cooling cycle) are closed for the long period if you manually advance the timer, and the normally open terminal 1 and terminal 2 contacts (defrost cycle) are closed in the short defrost portion on the timer, which is exactly what should be happening. Testing the wiring harness with the timer unplugged, there is 120v across the holes for pins 1 and 3 (those run the timer motor). Checking the pins for voltage while the timer is plugged in is where I see a problem. I get 120V across 1 and 3 when it is in defrost mode (which explains why the defrost timer works and moves out of defrost), but there is no voltage at all when it goes into cooling mode. I'm trying to understand how that makes sense. Pin 1 is power and if there was no power to 1, then the fridge wouldn't cool (the connection between 1 and 4). So, it seems like it's something downstream from pin 3 that is disrupting the timer circuit, but I can't really follow it back to what may be causing that (I need better reading glasses?).

Every post I can find says to replace the timer if it isn't advancing, but that didn't work here.
It was my understanding that basic fridges are always supposed to go into defrost mode every X hours without regard to usage. Is there something that puts the timer on hold unless certain conditions are met?

This is not a newer 'smart' fridge (thank goodness!). No digital readouts or big control panels, just a couple simple dials for the temps and normally solid performance. It's almost 25 years old and the only thing I've done to it before this is to add a bit of charge a few years back. And it's had a couple light bulb changes (but there are 4 bulbs, so that was bound to happen).

Thanks!!!

 

[Budget Appliance Repair]

Defrost timer motor won't run as soon as it comes out of defrost - it has to run long enough to close the defrost bi-metal before the defrost timer motor will start running again.   When the defrost timer comes out of defrost it no longer has neutral until the defrost bi-metal gets cold enough to close again and supply neutral to the defrost timer motor thru the defrost heater and bi-metal.

If you install the wrong timer with won't work or if you get the correct timer with a flying lead to be put on terminal 1 or 2 if you put the flying lead on the wrong terminal for the wiring in the unit you are installing it in, it won't work correctly.

[Jack UvAllTrades]

Thanks, you are right!!! (not that you didn't know that already :)!)
I took the timer apart and switched the flying lead from 1 to 2, and it works now. Had I looked more closely at the internal schematic of the timer circuit on the fridge specs, I would have noticed when I was checking resistance that it was across the wrong terminals.

It's interesting, while my timer didn't have anything except the terminal numbers printed on it, I see other timers like mine listed as direct replacements (for 2162044) that have the schematic printed right on the plastic and show the flying lead going to 1. Somewhere along the lines of this-replaces-that, some bad info got loose, or maybe we're just expected to change the lead for certain models.

Thanks again! I can finally put the panel on for good since I don't have to manually advance the timer anymore.