Freezer won't stay cold

[Richard Kollmann]

Many of today’s refrigeration thermostats like the Veco are designed for modern variable capacity technology compressors like Danfoss BD unit systems. Coupling the Veco with its microprocessor software to the Danfoss BD electronic controller requires careful programming. Veco controllers are capable of switching off compressor if condenser temperature is outside the preset range This unit also has a frost management system and a auto defrosting function.

The justification to replace Veco controller is involved first in testing Danfoss control over compressor with Veco disconnected. It thermostat bypassed on Danfoss provides continuous compressor running the next step is reprogramming Veco controller with help of manufacture.

[a64pilot]

Originally Posted by MarkJ

I shall reiterate the excellent knowledge spewed forth but obviously unread, from my last post...


You can buy a 12 volt timer that turns on and off 16 times per day.
I use that to regulate my big fridge that basically only has drinks in it. Coming up to 5pm when Sundowners are called, all the beer is cold.
But when the batteries are low, 1am till 8am its only on 5 minutes per 2 hours...

Mark, you have a link to this timer?
My system has two large cold plates, I'm thinking about a large off time at night, but let it run continuously during the day when I have excess Solar. I think the large cold plates will maintain fridge temp during the off time.

[MarkJ]

Originally Posted by a64pilot

Mark, you have a link to this timer?
.

https://www.amazon.com/CN101-DC12V-D.../dp/B00A4PDMPQ

CN101a

https://antidiary.com/video/watch/vid47J0xfPHTk-hQZY

[a64pilot]

Thank you.

[leftbrainstuff]

Originally Posted by MarkJ

Hi Brad,

You say "when you open the lid" the compressor starts up again.

This sounds like a thermostat problem, doesn't it?

My big fridge had the thermostat chopped out by the previous owner (sunsail) so I put in a 12 volt timer that dies many sequences per day.

You could do my test if its the thermostat by putting the purple wire off the compressor. (Mine is purple, dunno about yours).

Then either replace the thermostat or go onto a time based method.

Could a corroded thermostat connection be the cause? As in clean it up and see?

Good place to start. You need to isolate components to root cause.

I recently replaced a failed frigoboat thermostat. Fridge now performs much better with the new thermostat. So there is clearly a performance difference between the same part numbers.

I still have an intermittent fault in the controller which needs a power down and restart to resolve. By isolating components I now have a better understanding when issues arise.

Many of the components are hit and miss for quality. This results in multiple unrelated failures and variability in performance when replacing components.

All the above requires you to develop good troubleshooting skills. You also need to spend time with these systems to fully understand them. When there is documentation I find it misleading, wrong or incomplete.

I notice this issue with most marine electronic systems. They do not have the quality and reliability of automotive and aerospace components.

[Typhoon]

Originally Posted by leftbrainstuff

Good place to start. You need to isolate components to root cause.

I recently replaced a failed frigoboat thermostat. Fridge now performs much better with the new thermostat. So there is clearly a performance difference between the same part numbers.

I still have an intermittent fault in the controller which needs a power down and restart to resolve. By isolating components I now have a better understanding when issues arise.

Many of the components are hit and miss for quality. This results in multiple unrelated failures and variability in performance when replacing components.

All the above requires you to develop good troubleshooting skills. You also need to spend time with these systems to fully understand them. When there is documentation I find it misleading, wrong or incomplete.

I notice this issue with most marine electronic systems. They do not have the quality and reliability of automotive and aerospace components.

The exact reason to keep these systems as simple as possible , electronics fail.

Yes I do use a electronic thermostat in my system because the design allows for it. This controller is 10 dollars easily found on ebay or amazon. At that price you can carry a few on board.

I have yet to have one fail on my boat or or anybody else's . I personally have six of them running 24/7/365 on my boat, controlling refrigeration and heating . If one does give up, which I doubt , it's an easy swap out , just snap it out of the panel pop in a new one, connect the wires, good to go .

I don't use any automatic speed control on my system, just a manual speed switch . Simple.

Regards John.

[Ding Duck]

Some suggestions you may want to try. As richard suggested, short out the C & T terminals and run the system. If you can measure the plate temp with another thermometer to verify your temp controller readings. Seems strange how it goes from -4 to +12 in a short time. Plenty of Insulation?

Verify the Temp Sensor/ Controller. I assume this is Electronic and if so, can you get the tech data for the controller/ Sensor. The Sensor will be either PTC or NTC, which means the resistance changes based on temp. If you get some resistors from Jaycar, use these to confirm the controller by connecting these in place of the Sensor. You may want something like a 390 ohm 1/4W resistor and a trim pot (500 ohm). Otherwise, some fixed value resistors and check various values to see if the controller is OK.
Check the Controller settings. Is it set to Hysterisis or PID Control? Suggestion would be to set the Hysterisis to say 5 degrees (?). Once temp rises 5 degrees above set point, compressor should start again.
See how this goes?
Good Luck