[BigWave]

Purchased new in 2002. Didn't notice the fridge problem for a while. It finally got too warm. Freezer has been fine.

When checked, the evaporator had a lot of ice. There was an ice puddle on the bottom of the freezer, and the evap drain plug was plugged with ice. Used hairdryer to remove all. Also had ice on diffuser.

During the next few days, fridge got warm even with diffuser completely removed.

Installed defrost parts (heater and bimetal defrost). I did not get to test the old parts as the evap was completely defrosted by the time I got the food out/backpannel off (about 4 days after hairdryer use).

Now the fridge maintains temp, but sometimes wanders high. Diffuser appears to work (checked a few times during diagnostic routine). It seems like the diffuser is not opening when it should, or is freezing when shut and not able to open. If I wedge a screwdriver in to open the baffles, it goes to normal temp.

I checked both thermisters (during diagnostics and on a meter). I do not know the exact thermister values, just made sure my reading went in the right direction when touching ice water or my hand. I think room temp was about 2.6 or so.

Could the diffuser working intermittantly, is it the controller (I believe it controlls the defrost, diffuser, and well as everything else), or something else? I think I could manuall regulate the baffle to get the right temp (sorta what I am doing now).

[PS Volunteer - Appguy]

Disconnect the diffuser wires and jam a screwdriver in to keep open. Periodically check the fridge temps. If now ok, you probably have a bad diffuser, but you also could have a bad control board. Check under fridg for the service info. paper. Manually put unit into defrost and verify defrost is working.
Please post results.

[BigWave]

I ran the diagnostic. The defrost cycles kicks off (i saw the coils defrost at the bottom and water start to drip). When I tested the diffuser, it cycled open and closed. Both thermisters checked okay as well.

[PS Volunteer - Appguy]

There are too many unknowns here, do the test I suggested.

[BigWave]

This morning the fridge was at about 50. There was some ice accumulation around the exit of the diffuser. I unplugged the diffuser (with it opened manually) and left it for the day. This evening the fridge was at 20. When I plugged in the diffuser it immediately cycled closed.

Also, there is more ice accumulation at the drain of the drip pan for the evaporator. The bottom of the evap has a light frost.

[PS Volunteer - Appguy]

All indications show a bad control board. If you unplug damper and keep the damper door 1/4 of the way open, you will probably get normal temperatures from 34-40
If so and there are no other problems, this sort of confirms a bad pc board.
You might want to just replace the damper door thermistor to see if that fixes it. I wouldn't trust an ohm check for this.