Refrigeration problems

[Perfect Excuse]

Refrigeration problem with a Grunert Polar Mate water cooled unit. It runs well for about an hour then starts to 'pulse'. The amp gauge jumps from about 6 to about 17, back to 6 and so on. The water spurts out the outlet with corresponding rhythm. As the amps gauge spikes, there is a click from the cooling unit. My first though was plugged strainer, I cleaned that completely. I took the water pump apart it seems fine and runs well. If I turn it off when it starts to pulse and let it sit for 1/2 - 1 hour. It will start and run fine for about an hour. The fridge and freeze's thermostat had both been removed when I bought the boat, so I operated it manually by turning on & off the breaker. Could the problem be the fan relay? As anyone had a similar problem? Suggestions?

 

[Benny17441]

Hard to diagnose on-line but I would check the following; 1) make sure the strainer is clean and that you have good water flow from the thru-hull scoop (if in doubt disconnect hose and blow compressed air down the fixture) , 2) make sure there are no kinks or loops in the intake hoses to prevent air lock 3)make sure the pump is mounted below the waterline, 4) make sure all the wiring connections are clean and tight. It may seem the pump could be loosing suction perhaps due to air in the system, a blockage in the water conduits, a pump malfunction due to a voltage drop or an internal failure. If everything checks out perhaps bench testing the pump would be the next step. Connect intake and discharge hoses to the pump and use a bucket above pump level to recycle the water and let the pump run for at least two hours to see if you can duplicate the failure. Lastly sea water can create growth and scales in the water conduits and constrain water flow. Flushing the unit according to manufacturers recommendation might be necessary if obstructions are noted.

 

[Perfect Excuse]

Thanks Benny. I have done all that suggested. The symptom that I can't explain is the click associated the pulsing. My thinking is that may be the pump relay switch. We"re in La Paz, so I have limited resources and would like to know if I could jump the relay if I can't get another. Suggestions?

 

[woodster]

Thanks Benny. I have done all that suggested. The symptom that I can't explain is the click associated the pulsing. My thinking is that may be the pump relay switch. We"re in La Paz, so I have limited resources and would like to know if I could jump the relay if I can't get another. Suggestions?

you can jump the relay but you may need to do a standby and monitor the unite so as to shut it off when the system closes down other wise you may burn something out.... that relay may be the one that excites the compressor and scene the pump is not flowing good it may just be kicking in and out with the spurts...best to get the pump flowing 100% and then see what happens problem may be solve when pump is working again with even flow also check your wire connections and make sure they are good and solid especially the ground

 

[Stu Jackson]

Have you checked on Richard Kollmann's site? http://www.kollmann-marine.com/Performance problems.aspx

He posted here recently that 99% of fridge problems are electrical.

 

[Benny17441]

PE go ahead an replace the relay or adapt a substitute one. It is basically an inexpensive repair worth a try. The symptoms are indeed consistent with a relay failure. If you were thinking about jumping the relay as a fix rather than a test I would advise against it.

 

[woodster]

PE go ahead an replace the relay or adapt a substitute one. It is basically an inexpensive repair worth a try. The symptoms are indeed consistent with a relay failure. If you were thinking about jumping the relay as a fix rather than a test I would advise against it.

i just went back a reread your op i will have to agree with Benny on this... sounds like the contacts are burning up on the relay and letting it drop out

 

[Perfect Excuse]

Found an expert here in La Paz, turns out to be a simple low on freon. Too obvious. Arn't boat problem supposed to be more complex? For anyone interest the expert is Bob at Inflatable Boat Repair, La Paz.
Thanks everyone for your concern. Bob Bear

 

[Benny17441]

It crossed my mind but since you indicated the unit would run well for about an hour I just took it to mean it was also properly cooling. This is the reason why I don't like jumping relays or circumventing safety shutoff systems. Was the unit freezing up? It is usually a tell tale of low Freon. Glad you found the problem and the fix is quite inexpensive.

 

[Brewgyver]

It sounds like the circuit has a low pressure safety, which would explain the click, but if so the unit shouldn't have run for any appreciable length of time.
Also, low on Freon is not simple. Did he locate and repair the leak? Pressurize with nitrogen to confirm the repaired leak was the only one? If it's the kind with quick connect fittings on the line set, the connectors are the most likely location for leaks, but they could be anywhere in the circuit. The newer polarmates have dye in the circuit, so plug in a black light and look around.

If the tech just pumped some refrigerant into it, the problem WILL recur.

 

[Benny17441]

Just keep the unit under observation to see for how long it will operate with just a Freon refill. Don't know what the condition may have been with the low pressure switch to allow the unit to run repeatedly for up to an hour before cutting off but I would suspect its reliability should you start having problems again. I concur with BrewGyver in this regard. The switch seems to have worked erratically at best.