Is our fridge running too frequently ?

[heraulc2]

Hello,
I would appreciate any help with the following.
We have an Adler fridge, which until 2 weeks ago was running fine. Since then (no change of location or weather, filled to the same level, same operation), it has been cycling on/off too frequently, draining our batteries (replaced 6 months ago and in good condition).
We replaced the lid on the top door, added some insulation foam where we saw a small gap. Nothing changed..
We called a refrigeration guy who added some refrigerant and just replaced the thermostat.
The fridge has now been on for over an hour... so we decreased the thermostat from 3 to 2 and it finally stopped... But 10 minutes later, it started again for 2 minutes. Is this cycling frequency normal?
Thank you

[daddle]

No. The ON time should not be 2 minutes. ON time should be more like 20 minutes or longer. Might be an electrical connection problem with supply or thermostat. Careful testing with a voltmeter may be required.

[heraulc2]

Thank you. Electricity is not my forte. Can you please describe the steps I should follow in order to test all the connections? I see the + and - cables at the back of the compressor, and followed them all the way to the circuit breaker and terminal strip for the + and ground plate for the -. Also, although the compressor cycles on and off but at too short intervals, could the fuse be faulty or would it then not start at all?

[senormechanico]

If there's nothing in it, it won't run very long.
It's all about the percentage of run time, not how long it runs.
It is more efficient with stuff inside, as the first minute of run time doesn't really cool the box, it just ramps up the refrigeration coolant pressure.

[heraulc2]

It runs around 40% of the time. 3 minutes on 4-5 minutes off. Indeed it is not very full anymore since we've lost some food. we will fill it in a little.

[Noname]

Some thermostats have a "swing" setting; that is widening the variation between "on" and "off" points. A narrow swing setting causes more frequent on/off cycling and a wider swing setting causes a longer time between on/off cycles. Check the manual for your new thermostat to see if there is such an adjustment. Most household type thermostats will have this type of adjustment; but I don't know about the marine fridge type.

[onestepcsy37]

i'm no refrigeration expert, although i did remove the crosby engine drive fridge that the boat came with and replace it with an adler barbour setup. i've had it for six years now and it's run faultlessly, although when i first installed it it wouldn't run properly, i called adler barbour, they diagnosed it as a faulty control box, and fedex'd me a new one the next day - free of charge.

since you're fridge was running perfectly for years and then suddenly changed cycling frequency i can only suspect two places; the thermostat, and the control box. if you're happy with the thermostat, you might want to call adler barbour to see if they can diagnose the control box.

not sure if you know this, but the control box has a fault indicator light on it. it flashes fault codes when the box isn't working correctly. watch the fridge while it's running and see if the control box flashes fault signals when it stops. if it does, adler barbour (or your manual) might be able to tell you what the prolbem is.

another good source is richard kollmann, who occasionally posts here. he spent much of his life installing boat fridges in fort lauderdale; he's retired now but still keeps active including writing a couple of books on the subject. his website is kollmann-marine.com and i think you can ask him questions there and he will answer you.

[Richard Kollmann]

You are not going to solve the short cycling problem by filling box with product. The most likely cause of two minute cycles is thermostat's small temperature sensing tube is contacting evaporator where it should not. Five inches of sense tube at its end is the only part of tube intended to contact evaporator or cold tubing. Voltage drop in boats wiring will also cause Danfoss's control to stop compressor and allow it to run again in 2 to 3 minutes.

[daddle]

As Richard says, a voltage drop will cause the unit to short-cycle. Doing nothing useful. With a good voltmeter confirm that the voltage at the terminals of the controller, while it is running, is close to the voltage at the battery terminals. A couple of tenths drop (0.2V) might be acceptable.

The main suspect is the fuse you mentioned. They are nothing but trouble. Especially the inline type. You can often find voltage drop problems by touch. A bad fuse holder or connection will often be warm to the touch after a few minutes of the device runnning. All the connections should be suspected. Positive and negative. even the connections that look nice. No boat connection, switch, fuse or breaker should ever be warm to the touch.