Mystery Continued.....

Cont'd from before.....most excellent reading if you are into DIY work!!!

THIS IS WHERE I FLY OFF ON A TANGENT:

Actually, not to put too fine a point on it, but once the defrost cycle is over, the defrost timer DOESN'T actually turn on the compressor and fan. That's because the fridge might not need any cooling right then. At the end of the defrost cycle, the defrost timer restores power to the fridge's thermostat (more correctly called a "cold control"). The thermostat then closes the circuit to the fridge's compressor and evaporator fan only if the fridge needs cooling.

In the rest of this post, the word "thermostat" will be used for both the cold control and the defrost thermostat, but it should be obvious from the context which thermostat is being referred to.

So, the defrost timer switches power between the defrost heater and the fridge's thermostat (or "cold control"), and the thermostat then inturrupts that power or allows it to flow to the compressor and evaporator fan simultaneously.

So, typically, both the evaporator fan and the compressor motor will both be running (or both be not running) at the same time. If the compressor is running, but you don't detect any breeze whatsoever in the freezer compartment with your hand (or by the smoke rising from a lit cigarette or piece of smoldering cotton string), then it indicates a problem with the evaporator fan not working, and therefore no cold air being blown into the freezer and fresh food compartments.

Similarily, if the evaporator fan is blowing air, but the compressor is not running, it could be a problem with the compressor motor, perhaps the starting relay which starts the compressor motor.

Having the compressor and the evaporator fan both off at the same time is normal. The fridge may be cold and the thermostat has shut off the cooling circuit. Alternatively, the fridge could be in a defrost cycle. However, if both the compressor and evaporator fan are off for what seems like an unreasonably long time, and the food in your freezer is starting to melt, then there's a good liklihood that the defrost timer is STUCK in defrost mode.

AND THIS IS WHERE I COME BACK TO THE SUBJECT AT HAND.

The defrost timer location will be different on every fridge, so you have to find out where it is on your make and model.

Defrost timers will have their output shaft exposed so that if you mark the position of the shaft on the timer with a felt pen, you can check it an hour or two later to confirm that the timer shaft is turning. Also, having the output shaft of the timer exposed allows an appliance repairman to manually advance the defrost timer to check the operation of the defrost heater and defrost thermostat to see if they're working. This is normally done by turning the output shaft of the defrost timer with a screw driver, but since you can damage the timer by turning that shaft backwards the screwdriver slot will be designed in such a way that the shaft can really only be turned in one direction with a screw driver.

If you ever notice that your frost free fridge has suddenly stopped working completely, it's worth advancing the defrost timer to see if the fridge is stuck in defrost mode. If you hear a "click" and the fridge comes back to life, then the problem was that the defrost timer was stuck, probably in the defrost mode. That tells you it's a good idea to replace your defrost timer before that happens again.

If, on the other hand, if the defrost timer is stuck in the "run" mode, or the defrost heater isn't working, the usual result will be frost forming around the cold air vents in the freezer compartment, and frost forming in your frost free fridge's freezer compartment. In that case, advance the defrost timer until the compressor and fan shut off, indicating that the defrost timer is now diverting power to the defrost heater instead. Try manually advancing the defrost timer to perform several defrost cycles in a row to melt the accumulated frost. If doing that doesn't help, then the defrost heater is probably not working and needs to be replaced. Normally, a repairman will also replace the defrost thermostat at the same time as he replaces the defrost heater because the cost of the defrost thermostat is only 2 or 3 dollars. So, replaceing it at the same time as the defrost heater is mostly a matter of preventative maintenance. Those 2 or 3 dollars could save a $50 or $60 service call a few months down the road.

Finally, if you ever see water dripping from the roof of the fresh food compartment of your frost free fridge, the problem is that the melt water from the defrost cycle isn't draining away. Most often the problem here is that dirt has clogged the drain hole in the drip pan under the evaporator coils. There will normally be a cover of some type in the freezer compartment of your fridge. Removing that cover exposes the fan and evaporator coil (which is easily damaged because of all the thin aluminum fins covering it's surface). By poking a flexible (stranded) wire into the drain hole of the drip pan under the evaporator coil, you can usually unclog the drain hole and allow the melt water to drain away as it should.

IF YOU DON'T READ ANYTHING ELSE, READ THE FOLLOWING:

SO, If you come home from work on a friday afternoon and discover your fridge has decided to quit working, proceed as follows:

0. If it's winter, store the perishibles in the trunk of your car to keep them frozen. Keep the fridge door closed as much as possible to keep the interior of the fridge cold.

1. Does the fridge light come on when you open the door. If not, then the fridge isn't getting power.

2. If there's power to the fridge, listen to see if the compressor is running at all.

3. If the compressor is running, try to detect a breeze in the freezer compartment. If there's no breeze, the problem is that the fan isn't turning.

4. If the compressor isn't running, but the fan is, then the problem is most likely the compressor's start relay or something called the "start capacitor" or the "run capacitor" which the compressor motor needs to start.

5. If neither the compressor nor fan are running, then the fridge may be stuck in defrost mode and the prime suspect is the defrost timer. If you know where it is on your fridge, advance the defrost timer manually by turning the output shaft with a screw driver.

6. If the fridge doesn't spring to life now, then you've covered 90 percent of the most common problems, and it's time to call a repairman.

IF YOU DON'T READ ANYTHING ELSE, READ THE ABOVE.

It's standard practice to replace the defrost thermostat whenever the defrost heater is replaced. That's because it's an inexpensive part, and replacing it whenever the defrost heater is replaced is good preventive maintenance.

Normally, the defrost timer is only replaced as needed. However, since it's the "brains" behind a frost free fridge, I think it's a good idea to replace the defrost timer every 10 years or so. If you wait for a sale, you can buy defrost timers for under $10 each. If you have to buy one in a hurry, you're looking at $20. If you have to pay to get your fridge fixed in a hurry, the company fixing your fridge will prolly charge you about $35 for it. It's best to replace it every 10 years or so for about $10 a pop.