F&P N210 freezer defrost problem

[daringpeter]

I have a F&P freezer which is not defrosting. I replaced the defrost timer (which on test was faulty) with an identical, electronic one. However, it still will not defrost automatically- but I can do it manually by pushing the 'test' button, showing that the cabinet defrost components are OK.

The schematic (found on line) shows the phase supply going directly to the thermostat, then to the defrost timer. My question is, is that correct for a electronic timer? The parts list shows that the original timer, which may have been motor driven, was later replaced? by the electronic? one. I can see that a motor driven timer would retain the total 'run' time ie continue to accumulate time whenever energised, but does the electronic one? Can anyone help?

DP

[TVguy]

A mechanical defrost timer suggests the fridge has some miles on the clock. Defrost cannot run when the compressor is running, hence the connection to the thermostat.
The electronic alternative will have a timer that is simply based upon compressor run time. Adaptive defrost is adopted in modern refrigerators that bases defrost timing on door opening frequency.
Unlikely your electronic alternative is so sophisticated. Perhaps you could post a link to the schematic?

[daringpeter]

A mechanical defrost timer suggests the fridge has some miles on the clock. Defrost cannot run when the compressor is running, hence the connection to the thermostat.
The electronic alternative will have a timer that is simply based upon compressor run time. Adaptive defrost is adopted in modern refrigerators that bases defrost timing on door opening frequency.
Unlikely your electronic alternative is so sophisticated. Perhaps you could post a link to the schematic?

[TVguy]

Link reports a "bad request".

[daringpeter]

then select F&P and N210.

[TVguy]

Do you have an image or schematic diagram of the electronic timer? Does it has the same four terminals as the mechanical original?
You have demonstrated that the relay will energise the heater using the test switch. Clearly an electronic timer needs to be energised to run; therefore, it needs a permanent active connection.
Perhaps the module has a jumper or extra active connection to ensure it keeps time. Constant power cycling from the thermostat will be resetting the timer, never allowing it to accrue sufficient time to activate defrost.

[daringpeter]

It looks exactly like the pictures of what I think is a mechanical timer (sourced from the USA). I say think, as I have looked at the USA manufacturers web site, and I think it mentions 'synchronous motors". And it is drop in replacement- fits the cable loom. All very strange.