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Parts for Amana SRD23VW / P1315306W W - AppliancePartsPros.com

First remove the evaporator cover in the freezer so you can see the coils.
If they are heavily iced/frosted over then it is a defrost problem.
Do not let them de-ice.

If yes.
Manually force a defrost cycle by turning the defrost timer cam till the fans and compressor turn off.
There is usually a hole in the cover to let you do this without taking anything apart.
Now check the defrost heater to see if it is on.
Be careful you do not want to burn your fingers.
If the heater is on then the timer needs replacing, re: it is probably stalling during it's rotation so is never getting into a defrost cycle.

If not on.
Unplug the unit.
Remove the wire for one side of the heating element from the wiring and measure it for continuity, usually around 20 ohms or so.

If the heater is OK
Remove one wire to the defrost thermostat and measure it, should be 0 ohms when frozen. Note that it opens just above freezing so must be frozen to check it. Also inspect it, if it is bulged at all replace it even if it measures OK.

If both the above are OK then odds are the defrost timer contacts are toast.
Best way to test this is a live test to see if you have 120 volts across the heater/defrost thermostat combo.

[COLOR="Blue"]I saw that the defrost t-stat was on its side laying on top of the wires caked in ice. I`m wondering if it took so long to defrost because of that.[/COLOR]

I am not sure what effect the above would have.
My guess is that it would keep the defrost heater on for a longer time than it should as it is not measuring the coil temperature but it may just as well cause the heater to shut off before all the frost melts off the coils. It would depend on where exactly it was laying.

Just in case you do not know what the thermostat does below is a bit of an explanation.

The defrost time is a set time usually around half an hour.
So when defrost starts the defrost thermostat is frozen (closed) and the heater is turned on.
But lets say that the coils are defrosted after 20 minutes then the defrost thermostat will open killing power to the heater. It opens just above freezing.
The defrost cycle will continue for another 10 minutes but the defrost heater will be off.
This ensures that the defrost heater does not add too much heat into the freezer which could start to melt the food.