Whirlpool fridge Freezer evaporator freezing up

Jarvey

All,

I have a Whirlpool American fridge freezer and noticed that the evaperator fan is runing a lot more that it used to be. When i removed the covers in the rear of the freezer i found the evap all frozen up. I have checked the resistance of the heaer which is fine at 87 ohms, checked the bimetal thermistor which closes when frozen and opens around 3 degrees. I have confirmed that both the thermistors in the fridge and freezer are good also.
When the fridge powers up it gos into defrost mode for 15miins (according to service manual i found on web) so i checked the voltage been applied to the heater element after its powered on and it is only geting 150V AC.
All of this leads me to think the issue lies with the rear control board but its a costly item so im reluctant to order it without someone in the know confirming what i have done. I guess my real question is does anyone know what voltage should be applied to the defrost heater element during the defrost cycle.

ellewood

Jarvey wrote: »

All,

I have a Whirlpool American fridge freezer and noticed that the evaperator fan is runing a lot more that it used to be. When i removed the covers in the rear of the freezer i found the evap all frozen up. I have checked the resistance of the heaer which is fine at 87 ohms, checked the bimetal thermistor which closes when frozen and opens around 3 degrees. I have confirmed that both the thermistors in the fridge and freezer are good also.
When the fridge powers up it gos into defrost mode for 15miins (according to service manual i found on web) so i checked the voltage been applied to the heater element after its powered on and it is only geting 150V AC.
All of this leads me to think the issue lies with the rear control board but its a costly item so im reluctant to order it without someone in the know confirming what i have done. I guess my real question is does anyone know what voltage should be applied to the defrost heater element during the defrost cycle.

Are you 100% sure the bi metal stat is working correctly?
Can the melt water drain away properly?

Jarvey

ellewood wrote: »

Are you 100% sure the bi metal stat is working correctly?

Can the melt water drain away properly?

Thank you for your reply
There is continuity across orange and white wire from bimetal stat when i check it with frost all over the evap. At this point there is only 150v going to heater. When I defrost the evap or remove bi met stat the circuit opens as it should. As far as I can tell heater element is NOT heating up to melt the ice so there is No water to drain away. Once I defrost it water drains to drip tray underneath fridge.
I haven't tested to see exactly what temp the bimetal stat opens or closes.

Jarvey

Just in case anyone has similar issue. I replaced the rear control board and fridge is working fine again.