Cruisair Stowaway near LRA/RLA amps and popping breaker at startup

[codingparadox]

One of the three 2008-era Cruisair 18k Stowaway units (SXUF18/1-HV-RMT -- 115VAC version) on our boat has been tripping the breaker periodically for a few weeks now, running the heat nearly constantly in the Baltimore weather. It would always trip during compressor start, the standard problem. A couple days ago, it tripped for its last time, and no amount of waiting was letting it come back to life. So today I dug in a bit.

When the compressor cuts in, my clamp ammeter shows a rapid climb up to ~72 amps peak draw before the breaker (25A) trips. The LRA/RLA on the unit is listing 79 amps, so I'm guessing we're real close to locked rotor status.

I pulled apart the wiring box and checked the start/run capacitors. The caps check out okay -- with my Fluke 115, the run capacitor checks at 57 uF, rated at 60 +/- 6%, the start capacitor checks at 51 uF, and I can't figure out what the rating is supposed to be (model # for the cap isn't pulling anything up either).

I checked resistance on the three compressor wires (at the wiring panel, so past a few feet of wiring) and got around 2.1 ohm, 1.8 ohm, and 0.8 ohm between the three pairs, which seems pretty low based on what I'm reading online, but it's not zero. The compressor is a Matsushita 2K21C126B, and I can't find specs on what the resistances should be.

If it had just flicked into this LRA mode all of a sudden after working perfectly, I'd suspect that the compressor had just shat the bed, but the slow buildup implies to me that something else is awry here, and my knowledge of A/C units is still pretty weak at this point.

Anything else I can check out? Or try beating on things with hammers?

I'm trying to extend life out of this stuff for another 3ish months while I design and build out a full chiller/boiler setup, so if this unit is dead, I'll just swap our helm unit (least used) out for it in the meantime, that's just going to be a fairly exhausting swap to deal with. I'm coming out of hernia surgery last week so I'm not supposed to lift anything, so this timing sucks pretty good.

[pesarsten]

Are there any Schraeder valves on the refrigerant lines? I was wondering if you could get a drop of oil out so you can smell it and check if it's burnt?

[codingparadox]

Two last checks I did after trying to read a bunch more online:
* I tried starting it with measuring current across specifically the start and run windings. Start winding was ~5 amps, run winding was ~71 amps. I checked voltage at run winding (to common) during this, and it was at 105VAC, a ~12% drop, but also it's pulling 71 amps, so that's not too surprising.
* I pulled the cap off the wiring at the compressor to check resistance there. Start to common was 1.8O, run to common was 0.6O, start to run was 2.4O. So, right at the compressor, run to common seems pretty damn low... But still significantly more than the 0.0-0.1Ohm I'd expect to see for a true short.

[codingparadox]

Originally Posted by pesarsten

Are there any Schraeder valves on the refrigerant lines? I was wondering if you could get a drop of oil out so you can smell it and check if it's burnt?

I tried briefly pressing in on the schraeder valves, but just gas came out, no oil of any trace that I could check for an appreciable smell. Didn't want to keep pouring R-22 out so only did a couple brief taps on each of the two valves tho.

[codingparadox]

Tried one last thing also of reversing start and run leads at the compressor, which made a different humming sound but did not seem to dislodge it at all. That kinda points to pretty seized compressor, it seems like.

[team karst]

How do the other two read? Does that meter measure inductance? That goes down quickly with shorted winding.

[codingparadox]

Unfortunately my meter only reads resistance/voltage/current/capacitance/frequency.

What other two readings are you asking about to check?

[team karst]

U mentioned three units total? A compare should be easy.

[codingparadox]

Been a super cold and also super busy week, so didn't get around to checking this until today when it finally warmed up on the holiday.

Interestingly, and surprisingly, the resistances on a working unit are right about the same -- 2.4/0.6/1.8. So it doesn't appear that the rotor has welded itself open/closed, it might just be physically stuck, not that that helps. But I tried running it again today and same result -- locked rotor hum, high current pull, and breaker blow.

Any other ideas anyone?

[Bowdrie]

Originally Posted by codingparadox

Any other ideas anyone?

Perhaps have a tech hook-up the gages and also check the operation of the reversing valve.

[codingparadox]

The problem is that by the time I pay the fee for a tech to come out and look, when they're free 3 months from now, I'm a long way towards just buying a new unit. This unit can just be turned off forever and it will be a minor annoyance but only that. I'll just replace it all with a chiller unit sometime this year.

[Tin Tin]

I did not read all the stuff, but did you trying running it in cooling mode?

[codingparadox]

Yeah, it blows there too.

[Bowdrie]

Originally Posted by codingparadox

The problem is that by the time I pay the fee for a tech to come out and look, when they're free 3 months from now, I'm a long way towards just buying a new unit.

Understandable.

[team karst]

Well, there is definitely a way to stop the breaker from tripping!