Monthly Archives: November 2011

GE Refrigerator Appliantology: Dampers and Thermistors

This is the next in a series of posts I’m doing about the technology used in GE refrigerators. Understanding the basics of how these refrigerators work will give you a lot of troubleshooting insight when you’re trying to track down a problem.

For the previous post in this series on controlling and operating the fan motors in GE refrigerators, see this page.

This post gives useful tips and Fun Facts to Know and Tell for diagnosing the Damper Door and Thermistors.

Damper Door

The Damper Assembly has two motors: one to open the Damper Door and another to close it.

The Damper Door should always be either fully open or fully closed; if you ever see it in a halfway state, there’s a problem. Check it in diagnostic/self-test mode where you can run a test to open and close the damper door.

Thermistors

Thermistors are basically variable resistors whose resistance changes with temperature. They come in two flavors: Positive Temperature Coefficient (PTC) and Negative Temperature (NTC). In the PTC thermistors, the resistance increases with increasing temperature whereas in NTC thermistors, the resistance decreases as the temperature increases. All thermistors used in GE refrigerators are NTC.

Most of the side-by-side units will have four thermistors:
– attached to the evaporator coil
– freezer space
– beer section space
– damper

You can see a diagram showing thermistor locations in side-by-side units here ==> LINK

Units with the Custom Cool feature will have a fifth thermistor for the Custom Cool compartment. Lower end units will just have three thermistors.

In all units, the thermistor attached to the evaporator coil is the most troublesome.

There was a rash of problems with one of GE’s old thermistor suppliers a while back where they weren’t sealed properly so moisture got into ’em and knocked ’em out of calibration. More about that here ==> LINK

The refrigerator control has a self test for the thermistors, but it only tests if they’re open or closed. In real life, the thermistors rarely fail that way– usually they simply go out of calibration resulting in poor temperature control.

To learn more about your refrigerator, or to order parts, click here.

GE Refrigerator Appliantology: Fans, Evaporator and Condenser

This is the first in a series of posts I’m going to do about the technology used in GE refrigerators. Understanding the basics of how these refrigerators work will give you a lot of troubleshooting insight when you’re trying to track down a problem. This post explains how the fans in GE refrigerators are controlled and operated.

Like most other refrigerators, GE refrigerators have at least two fans:
– the evaporator (freezer) fan
– the condenser fan (the hot coil in the back, underneath the refrigerator)

Some up-line GE models may have an additional fan:
– in the beer section if it’s a dual evaporator unit
– in the Custom Cool® compartment, if so equipped

All fan motors used in current model GE refrigerators (includes Hotpoint brand) operate on 12 vdc. The motor speed is controlled using a technology called Pulse Width Modulation (PWM). Simple explanation of PWM: take a square wave and vary the width of the upper side of the pulses according to how fast you want the motor to turn- the longer the pulse, the faster the speed. For details on how PWM technology works, see this page ==> LINK

Currently, the condenser fan is single speed (although that’s gonna change in upcoming models) and the evaporator fan is multispeed.

Fan Wire Harness Color Code

– Yellow: PWM signal (input)
– Blue: Tachometer (output from motor)
– Red: +12 vdc supply (input)
– White: Common Ground! Can I hears an “A-freakin-men?”

The PWM wire on the fan motor harness is always the yellow wire– this is the wire that carries the signal telling the fan how fast to spin. Don’t bother trying to measure the voltage on the yellow wire with a conventional meter because the results will be meaningless.

Quick n’ Sleazy Fan Test

– White wire to the negative battery terminal
– Connect BOTH the Red and Yellow wires to the positive battery terminal.
Do not reverse the leads or you’ll blow out the sensitive electronics built into the motor assembly!

Quick Fan Diagnostic Test

– you should never hear the the fan making speed varying sounds in side-by-side units
– on top-mount units, you can sometimes hear the fan making pulsing noises

Fan Circuit on the Muthaboard

Some of the Muthaboards used in these boxes have resistors in the power circuit for the fans. These will be two resistors coming off the J2 plug on the board. If you’re looking straight at the board, the top resistor is for the evaporator fan and the bottom one for the condenser fan. They’re designed to burn out in case one of the fan motors shorts out. If this happens, you’ll need to replace BOTH the affected fan motor as well as the Muthaboard.

Part Links for Your Shopping Pleasure 😉

Evaporator and Condenser Fans ==> LINK

Muthaboard ==> LINK

To learn more about your refrigerator, or to order parts, click here.