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Replacement parts for FRIGIDAIRE FRT18G4AW4 Frigidaire/refrigerator | AppliancePartsPros.com

Here is the wiring diagram
http://manuals.frigidaire.com/p...f/Anderson/240379007.pdf

I do not know the answer to your question.
But I think you are looking in the wrong area.
If the compressor and it's fan are running and the evaporator fan is not then odds are that you need a new evaporator fan.

I thought you were referring to the main temperature control thermostat.

Am I now correct in thinking that it is the defrost thermostat (Item 21 in Section 4) that you are trying to replace.
If you click on it's picture a better view will come up.
It comes with two inline crimp connectors and two wire nuts.
This usually indicates that the new thermostat will have to be spliced in.
I would not use the inlines unless you have a pair of crimping pliers.

With the thermostat not working the freezer keeps on running and running there fore freezes up those fins solid with ice. The thermostat tells the freezer its time to shut off so ice doesn't build up. I appreciate the reply though!
If the above is referring to the defrost thermostat then you have been mis-informed.
The defrost timer (Item 23 in Section 3) tells the unit when to defrost.
Tech sheet says this is a 24 minute defrost cycle once every 10 hours of compressor run time.
The defrost thermostat opens just above freezing so that if all the frost/ice is melted off the coils before the 24 minutes are up, it turns the heating element off so that additional heat is not introduced into the freezer.
The timer continues till the end of the 24 minutes and then restarts the compressor/cooling.

There may be some confusion on this unit the parts shows a defrost timer while the tech sheet wiring diagram shows an adaptive defrost board but it also shows a defrost timer in the wiring breakdown so I am not sure what it is.

I just did not want you going in circles.

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

If yes.
Manually force a defrost cycle by turning the defrost timer cam till the fans and compressor turn off.
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.

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.

There is a good STICKY at the start of this forum about it's use.