Waeco fridge maintains different temps at 120 AC and 12 volt

aero3113

YYZRC said:

That’s what mine did. Compressor would cycle on and off constantly when on DC power. Worked fine on AC. 

My cabin fridge does the same once my batteries discharge a little. I might have to do this mod.

YYZRC

My fridge ran all night last night with no issues. I think this is working!

Spyderweb

Update on my testing.  Turned off battery charger at dock for 2 hours to stabilize battery.  Voltage at battery was 12.75, tested at fridge when OFF, was 12.66.  Tested with fridge ON, dropped to 10.50.  I then disconnected the wires at fridge and ran 2 12 gage wires direct from battery to fridge.  With fridge OFF, had 12.73, when ON dropped to 11.69.

So, receiving power from the electrical panel there is a ~2 volt drop, when receiving power direct from house battery there is only a ~1 volt drop.  Also ran the test from a starter battery and got a similar 1 volt drop.  

In both cases, compressor seemed to be on.  Correct me if I'm wrong, but is likely that out on the water, it doesn't take too much falloff in the battery where the voltage is just too low, and compressor stops running?  And is the differential in voltage drop significant enough to indicate high resistance in the original wiring?

Further testing this past week took me into the electrical panel.  I removed the fridge wires from the breaker and attached to a different breaker and tested.  I got the same ~2 volt drop.  So breaker appears good.  Also pulled on all the ground buss wires and checked for loose screws.  All was tight.

My next thought is to run a test where 1 wire (red or black) is connected directly to battery, and leave the other original wire attached to the fridge.  Then turn fridge on and record voltage drop.  Reverse wires and try again.  I think that would isolate whether the resistance is on the positive or negative side.  If negative, I think I could fairly easily run a wire from the ground block near the batteries directly to the fridge going up the port side of the hull.

Is this a sound plan or am I missing something with my simple minded understanding of electricity?

And @YYZRC, You're voltage booster is my plan of last resort.  It just concerns me that boosting voltage to fix a problem (high resistance somewhere) is kind of a band aid approach.  The high resistance is still there, and can it get worse, cause more heat, smoke, etc.?

YYZRC

I think a 13 year old compressor is just not efficient anymore. Whether you can fix it by running heavy gauge wire directly to the battery or via the voltage step-up route I took, both are a temporary fix for what is really an old mechanical device that is nearing the end of its useful life. 

On my 330 I ran new heavier gauge wiring to the panel and it didn’t help. I believe the underlying issue is that the old compressor requires a lot of amps to get going and that brief period of high draw causes the control board to shut the compressor off as it senses voltage is too low. Maybe someone smarter than me can figure out how to add a capacitor to help even out the draw on start-up?

Spyderweb

Latest Update:  Was up to the boat this past weekend.  Planned to run the test mentioned above on the last day to isolate the resistance to either the (+) or (-) wires.  Meanwhile, went out on the water the 1st day and fridge acted as always, essentially warmed up all day when on battery until evening when freezer was 35 and fridge 55.  Went out next day, expecting the same thing, and freezer stayed 6-9. and fridge 38-40.  ALL DAY!  

It worked the way it's supposed to, as in cycling on and off all day.  Before I think it was constantly trying to start up, sensed low voltage, then shut down, then tried to start again... Essentially the compressor was drawing power all day and getting no cooling.  I even noticed less overall draw on my house batteries when it actually kept the fridge cold all day.  

My only explanation is that when I removed wires from fuse and tried a different fuse last week, then back to original fuse, it cleaned up the contacts enough to reduce residence.  But, why did it not work the 1st day out?  And will it still work next time up? Stay tuned.

Handymans342

Why you ask??? Because it’s a friggin Boat

Spyderweb

LOL

MarkB

Handymans342 said:

Why you ask??? Because it’s a friggin Boat

yup.

LaRea

(ignore this)

Spyderweb

Latest Update (hopefully last) - Went up to the boat for an 8 day stay.  1st 4 days out on the water, fridge worked perfectly all day (freezer 3-6, fridge 39-42).  End of the 5th day I noticed the fridge was high 40's.  I was leaving the "mothership" and headed out fishing with son in law and grand kids on his boat so didn't look into it.  Thought it was probably a fluke, or door left open, or wife added a bunch of uncooled drinks etc.  Got back in the dark and forgot about it. 

Next day wife and I were out on the water and I paid attention to it.  1st few hours, definitely working and holding temp.  In the afternoon it went back to its old way, fan running, compressor can't kick on, fan shuts off, 10 seconds later starts up again, and continues this cycle. All the while the temp increasing inside.  

Was really bummed. Didn't want to mess with taking the doors off the electrical panel to access the fuse again.  Next trip.  After awhile, I decided I would at least pull the fridge out and clean the contacts of the (+) and (-) of the controller.  Took fine sandpaper to them, plugged back in, and nothing.  Only the fan cycled on and off. 

Then I noted the pair of wires behind the fridge, the 12 volt feed wires, butt connected to the controller wires.  I gave them a hard wiggle and thought I heard the slightest waver in the sound of the fan.  Figured I had nothing to lose, so I cut them out and replaced with new connectors.  I plugged it in and heard the compressor shudder, as if turning on.  We sat and just stared at the thermometer, waiting to see if it would go up or down.  It went down.  Eureka!  Put the fridge back into the cabinet, and within about an hour, temps were back to normal.  

I'm claiming victory on this one!

LaRea

Bravo!  That was the issue with my cockpit fridge.  Those connections do not last forever in a marine environment.  

Liberty44140

Awesome!!

aero3113

Nice! I should replace mine. Always seems like on the hook on DC power, my cabinet fridge starts to give up later in the day. Same symptoms….

MarkB

There's always a reason! You found it!

YYZRC

Living the good life here! I adjusted the hinge on the cockpit fridge (the seal was binding) and it is now running great. 

Spyderweb

The numbers on the left side of my 1 year Accu Rite have deteriorated where several lines of the LCD no longer work.  The good news is my cockpit fridge maintained 36 all weekend.  Probably helped by the fact that the cabin was 74 and not 88 like it was a few weeks ago.