I changed the defrost timer on a cpf50c and lost my position tags on two wires. I need to find a technical manual with a wiring diagram.

2 and 4 are power for the timer 1 and 3 are load lines N is defrost termination.

sounds like a bad defrost terminator or timer wired wrong. won't make temp as the evap is not clear of ice/frost build up. check your wiring diagram for location and operation of terminator.

Melt the iced up evaporator with a hairdryer for a temp. fix. The auto defrost system isn't working. I can't find diagrams of yours but here is basically how it works.

The evaporator coil behind the cover on the back wall inside the freezer will ice up under normal conditions. Every 8 to 10 hours for around 20 minutes the defrost timer (or in most newer models the electronic adaptive defrost control) will turn the defrost heater on to melt the built up ice. There is a defrost thermostat which prevents the heater from overheating the freezer by breaking the heater circuit when the temp reaches close to 32 degrees F. The entire cooling system shuts off during the defrost cycle and starts back when the timer advances through the cycle.

If this ice is not melted it will continue to build up until the air can't flow over the coil to circulate the cold air through the freezer and into the fridge. The temperature change in the fridge is usually noticed first followed by the freezer.

If the defrost thermostat is bad, it can prevent the heater from coming on OR it won't turn the heater off when it gets too warm. It is clamped to the evaporator coil at the top to sense the temp. If it appears to be misshapen it is bad.
With an ohm meter it should show continuity when cold and none when warm.
You can also bypass(disconnect the two wires plugged into it and twist them together) the thermostat to see if the heater comes on then. If it does then you know the thermostat is bad and needs replaced.

The defrost heater is located on the evaporator. It is in a tube which is at the bottom and can also go up the sides of the evaporator. On some types you can see a burnt spot if it's bad. With an ohm meter it should show continuity from end to end when disconnected from the wiring in the freezer. You can also test the wiring for voltage when it's in the defrost mode.

If you have a defrost timer you can test it. It can be located under the fridge behind the kick panel on the front. Some are in the fridge with the controls at the top. You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer because that means the timer is not running. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.

If you have an adaptive defrost control instead of a timer, replace it if the heater and thermostat test good. It is located in the fridge with the controls in some models and on the back in others.

I have a generic wiring diagram that I use on all my installs that works very well. It is basically the same for most all commercial walk in freezers. Send me a email address and I'll scan and forward what I have.

Hi, installing a defrost timer is not difficult if you know what the wires represent. Since you don't have a manual and you are removing the timer that was put on in place of the original one, I would call the manufacturer of the freezer for help on this. If you mis-wire it, you can burn the motor for the timer out. The freezer it self should have a schematic diagram pasted on it showing the wiring for the defrost timer? Check on it and see. Keep me posted and I will continue to look for one.
Sincerely,
Shastalaker7

the freezer has a defrost timer and relay. if either is bad, it may get stuck in defrost mode(depending on what position the switch failed in). The fan will run constantly if this is the case. You may choose to follow the wiring diagram on the back of the service panel or hire a technician. If you do it yourself, unplug the unit for your safety

Most all commercial freezers have a fan delay/ defrost terminator. It is usually mounted on the end of the evap coil. It's purpose is to sense the temp of the coil during the defrost cycle. When it hits a preset temp., usually around 55 degrees or more (depends on Mfg.) It terminates the defrost cycle. It also doubles as a fan delay. It allows the evap coil to cool off from the defrost cycle before allowing the fan to come on. Usually, the coil has to get around 20 degrees before fan will energize. I would look for this as a possible problem. It could be one device with 3 wires or 2 separate devices with 2 wires each. I've seen it both ways.
Hope this helps.

You might check the defrost timer. They come set on defrost. You can usually use a screwdriver to turn the timer manually to get it to immediately start. I did not check the schematics for yours but you may also check that the cap. is of the correct uf rating and that the wires are in their correct position.

The cause if no defrost cycle , remove the panel where the ice is and derost with unit unplugged , use a hairdryer or similar to defrost ice , make sure its all defrosted , check the heater under that coil to make sure its still intact.
Also check the defrost timer , there may be a wiring diagram on the back showing where this is located.
Phil

almost certainly a problem with the defrost timer - just replace complete. doesn't matter what position you set timer to when replaced