Kitchen Large Electric Appliances - Need some specific advice on how to test the defrost

OK I've pulled it all apart and checked it out but I couldn't find any blow by blow diagnostics on here so I need some input. I believe the coil read about 25 Ohms - so I'm guessing it's OK. There was a lot of ice below the coil, in the small catch tray, but the fridge had been off for three or four hours by the time I could actually get the back cover off.

I found what I assume is the thermo switch attached to a refrigerant line just above the coil. There appears to be 120V going to the switch but not coming out of it. I tested with a Fluke light stick, not an actual volt meter, but the "stick" isn't supposed to trip below 90VAC.

I found what I assume is the time switch dead center behind the front kick panel cover. It looks similar to the switch in the picture. However I'm not sure how to test this or manually advance it. I can only say that there is an access hole where you can actually see a motor spinning. So I would say it's at least partly working.

So what should be happening here? Is there always voltage to the temp switch or is the fact that there is voltage at the temp switch mean that the time switch is working and the temp switch is shot? replacing the temp switch looks to be about a one minute job if the leads are the same and a ten minute job if I have to cut and splice/solder. Not sure what it would take to replace the time switch.

For the moment my food is safe but I would REALLY appreciate a reply here. I'm going to have seven people in this house starting Wednesday and it's going to be a real mess if the fridge is down. Thanks much.

OK - I've thoroughly cleaned and completely defrosted everything. I also blew quite a bit of debris out of the train tube. Turned it back on this morning and it took about four or five hours to get down to temp. I did not stay with it the entire time but every time I checked on the status the fan was running. So it would seem it ran about four hours straight. It's just down to temp now so I'll have to wait and see how well it cycles on it's own. It doesn't appear that it has run the defrost cycle at any time. The coils are showing only very minor frosting only on the front edge of the top row of aluminum fins. The compressor is also running MUCH quieter - less load now that all the ice is off of it?

I don't really know what all this means.

The timer is definitely running but it appears to be an early model with no way to manually advance it. Is it possible for a timer to run but the internal switches be shot to the point that it never goes, or only intermittently goes to defrost? In all of this the only thing I've really verified is that the unit cooling with reasonable effectiveness. Beyond that I still have no idea.

Unplug it and remove the thermostat switch. Put it in the basement freezer long enough for it tto reach freezing temp. Ohm it for continuity while it is still cold. This switch does not close until the freezer reaches a certain temp. Then it will let power through and turn the defrost heater on if it is not bad. Clipped onto the coils right? Just unclip it after unplugging fridge and remove the leads. You mentioned debri. Make sure the drain is not blocked so all the water can drain when it defrosts.
You could see the timer motor spinning? Not sure I have ever seen one spinning. Usually have a dial in the middle that can be turned with a screwdriver to advance it.

yes - you can actually see it spinning through a little access hole. I am positive you can't manually advance it either. I'm guessing this fridge is very late seventies to early eighties. That label has in big bold print "free o frost freezer compartment!!!"

I tested the coil and temp switch by pulling the timer and hardwiring voltage straight through. Coil came on strong and melted everything. The temp switch opened after about ten minutes. put it all back together. The fridge has been running almost not stop to keep the temps down and the coil is starting to ice over again. I have no idea how often the defroster is supposed to run though. Once every hour? every 24 hours? What?

I'll see what it's doing in the morning. I may throw a timer in it for good measure but after that it's time to call a repair guy to see if there is something I'm missing.

Not sure what your original problem was but in your recent post where you stated the coils only had frost on some coils after hours of running sounds like the unit is low on freon. All coils should have an even coating of frost on them after a few hours of run-time. If coils aren't cold enough near the defrost thermostat, the timer will go on defrost but the thermostat won't be closed to let the power go to the heater.

Ditto on the spotty frost pattern. Low refrigerant or contaminated coils.

The frost was reasonably consistent. Developed frost first on just the front edge of the aluminum fins of the top coil but seemed to set in fairly consistently across all coils over the next few hours.

The fridge seems to be working pretty well now. Not sure what the original problem was but the drain was definitely full of debris, if not completely clogged. The timer was working but I replaced it, suspecting that it was on it's last legs and may have been intermittent. When it was running the little electric motor was HOT. Burn your skin type hot. I also guessed that the drip tube had a plastic piece at one point that extended to a bit of a well around the outside edge of the bottom chasis. This is the only thing I can see that could be considered any sort of drip pan. So I added a piece of tubing to move the water to that well.

It's been about four days now. No water on the floor, no heavy frost in the freezer and it's maintaining temps. It is certainly due to be replaced and probably should be checked out by a real service tech but if I can get buy without sinking any more money into I'd rather just replace it as soon as possible. I'm guessing a service call would end up being a couple hundred which is ten to twenty percent of what I need to retire the old girl.

Thanks for the help.