Frigidaire FFFH20F3WW upright freezer green flashing light and beep

OK, so last night I put everything loosely back together again and fired her up.

The green light stays constant (as it would normally) but there is no action. The freezer is on, the light inside comes on when the door is open and when I put it into test mode, it fires up. But only in test mode.

In test mode, the evaporator coil began to get cold and the defrost heater got hot, which would indicate that the heater is working.

I just disconnected and tested the resistance of the defrost thermostat and temp thermostat and did get readings of around 13 Kiloohms. The multimeter was set to auto and so chose the kohms option. When I changed the range to ohms, i got OL for both thermostats.

I also checked the potentiometer and got a variable reading when the knob was turned. I had probes on the orange and yellow wire.

Any further ideas/suggestions in light of this info? What would be preventing the freezer from automatically firing up? I was really hoping it was a faulty thermostat!

Also, thanks so much for your help

@adhoc33589

Just verifying that you performed two separate tests whilst in service mode i.e. Test ! and then Test 2 and not that the heater turned on when the compressor was still running?

If you exited Test mode as described and it didn't start as it should then perhaps check if the temperature control potentiometer voltages as seen on control board J3 connector are as shown.

I can only think of two reasons why it doesn't start when it should:

1. The temp control pot is indicating that it is cold enough so no need to run the compressor to cool things down to the set temp. - did you test between the brown and orange wire or even the brown and yellow wire, also did you unplug it from the control board when you tested it to prevent incorrect measurement due to a parallel circuit connection in the control board?

2. For some reason it may be still in defrost mode for some reason. Did you try a manual defrost when not in test mode? If it doesn't work then it may still be in this mode. Stupid thought perhaps by try waiting for 67 minutes and check if it turns on after leaving it in normal mode.

After entering service mode, I cycled through all 4 tests.

I followed this guide on YouTube - https://www.youtube.com/watch?v=vN5hvM2k...

I did not actually check whether Test 2 : Defrost Heater, started the heater. I followed the video and took Amp readings behind the freezer.

The only test that didn't receive any Amp draw at the back was for the evaporator fan. However, I checked the fan and it is fine.

I disconnected the pot and tested the resistances. The only readings I got were between the orange and yellow wires. No other combo received any reading, just OL. I assumed this was maybe the wiper?!

to answer your first question - I'm pretty sure that the heater came on whilst in Test 1 whilst the compressor and condensor fan were running behind. I will double check this.

I will also try manually activating defrost with the 5 magnetic touches and see what happens.

I can confirm that all tests worked as they should.

First test - fan and compressor turned on.

2nd - defrost heater started.

3rd - interior bulb on

4th - evaporator fan started.

Unsure as to how to check voltages on pot which indicate +5v.

Maybe the lack of readings on the pot wires would indicate a problem?

@adhoc33589

If you didn't get any resistance reading when using an Ohmmeter to directly measure the temperature control pot between the brown and yellow wire terminals of the pot (or between the brown and orange wire terminals) then the pot is faulty.

You should get a resistance reading when measuring between the yellow and the brown wire terminals on the pot as this is the full range measure of the pot and not just part of it as it is when measuring between the yellow and the orange. Make sure that it is disconnected from the harness cable or whatever and measure on the pot itself.

The pot is used as a voltage divider i.e. current flows from the yellow to the brown and also from the yellow to the orange and depending on where the orange wire which is connected to the wiper is along the coil resistor or whatever it is in contact with e.g. it could be a graphite resistor will alter the amount of voltage being "seen" by the control board indicating at what temp you would like the freezer set to. The voltage signal value = the desired temp setting or even "off".

It may be and I don't know if this is correct, that if the control board "sees" the full 5V which it will if the section of the pot between the orange and the brown is open circuit then this might indicate the "off" position on the pot so maybe that's why it doesn't turn on

For example there is 5V DC supplied to the pot by the control board but essentially the 5V is divided into 2 voltages i.e. the voltage drop on the pot between the yellow wire and the orange wire and the voltage drop on the pot between the orange and the brown e.g. it could be in the ratio of 3:2 or 4:1 or 1:4 or even 5:0 if this does indicate the off position etc depending where along the pot the wiper has been positioned by the user adjusting the temp setting.

The voltage value on the orange wire is translated into a temperature value and this is compared to the resistance value of the temp sensor in the air column which is also translated into a temperature value so the control board knows whether to cool things down further to what you want or turn off as it is cold enough.

This is also with the proviso that it is operating withing the standard upper and lower preset temp limits for your freezer of 4°F → -4°F. All the temp control pot does is allow you to vary the temp within this range or to turn the unit off.