You asked: So my question is does something halt the timer (defrost terminator?) by sending a live to terminal 1 which feeds the capacitor if it is heavily frosted in the freezer? am i best manually defrosting freezer and see if this makes a difference '
The answer is yes the motor for the timer is stopped temporarily by sending a live to terminal 1 when the single pole changeover contacts move from position 4(compressor run) to 2(defrost). See my diagram below. The live passes through the defrost stat (DFST). The motor M has a live on 1 and 3 so there is not potential difference across the motor to cause it to run - thus the mechanical timer stops.
What now happens in defrost mode is current passes from Line L through contacts 3-2 and the DFST to the defrost heater HTR. The compressor C has no power because contacts 3-4 are open. Over time the heater HTR warms up the evaporator and when the temperature exceeds 0C the ice and frost starts to melt and fall away. The heater remains turned on until the frost stat DFST detects the evaporator has exceeded 6C. With the compressor still unpowered the block of ice can only melt further and hopefully fall away from the evaporator.
Because the frost stat DFST has opened terminal 1 is now connected to Neutral N via the low resistance of the heater HTR. There is now a potential difference equal to the mains voltage across the motor M which starts to turn the timer mechanism. After a dwell of 7 minutes the contacts 3-2 open and 3-4 close which switches from defrost mode to compressor mode for cooling.
I hope you can see now that the voltage on terminal 1 will be live during the time the frost stat and 3-2 are both closed and low otherwise.
The key thing to note is that during heating the timer motor is stopped. How long the timer remains stopped depends on the power of the heater, the temperature of the ice and how much ice has accumulated. It is perfectly normal for the timer to be stopped while it waits for the frost stat to open at about 6C. I show this in my diagram as time duration x.
The 7 minutes dwell/delay after reaching 6C is to allow some time for heat to flow through the block of ice for the phase change from solid to liquid to happen ie the ice to melt and fall away.
The run time of 12 hours is an accumulated compressor run time not 12 consecutive hours. This is because the line input to the frost timer terminal 3 is via the freezer temperature control stat which of course cycles on and off. Thus even when contacts 3-4 are closed motor M only runs when the control stat is closed also.
If then the evaporator is very iced up it could take some time before you hear the timer motor to start up and implement the 7 minutes dwell/delay before resuming cooling.
Why did you think the capacitor needed replacing?
Might it be the evaporator was unusually heavily iced up and it is just taking much longer to melt and fall away. In which case you could manually defrost by turning off the power to the freezer completely and waiting for it to melt away. Then dry down evaporator and power up comletely again. Check drain hole is clear for melt water to clear away.
PS: Your timer is for a so-called Type 1 defrost wiring scheme which means motor M between 1 and 3. A Type 2 wiring scheme has motor M between 1 and 4.
Many thanks for this info.
We had manufacturer engineer visit to rectify fridge freezer. His conclusion was that defrost timer was faulty, but manufacture said part was obsolete. Having looked inside timer i could only assume the capictor was at fault or motor winding. took the chance on capictor and the new one when fitted the cogs started turning. However it advanced into defrost mode and as explained cogs then stopped turning.
i have since completed a manual defrost of freezer and then switched back on. Again timer cogs turned in cooling mode and fridge freezer working, but before it went into defrost mode the cogs stopped again, so unsure if still faulty.
Questions i have are: would the visiting engineer swapped over wires on defrost timer termials to enable fridge freezer to work only in cooling mode???? As per picture the wiring configuration is how i found them.
I have now sourced a exact same timer make , volts times etc, but worried if fitting will cause it harm.
To confuse things further i contacted manufacture explaining problems as per this posting and asking for wiring diagram. Only response i have had is that their technical team say the defrost timer should always be turning, and that a faulty defrost heater could be sending the power to terminal one
email reply from hoover candy
Our technical team have advised "The timer turns the heater on and continually carries on turning. Normally set to come on around every 8hrs. If defrost heater is faulty it will cause the timer to stop. This could be the heater is open circuit so that’s why the timer stops."
So i am at a loss with this now. Have asked that if defrost heater is available to get a manufacture engineer out to re look at problem and fit the new defrost timer.
But cooling still seems to be working, but when advance manually to defrost it doesn't activate.
