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Roger7500  
#1 Posted : Monday, March 5, 2012 11:56:29 AM(UTC)
Roger7500

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Noted that freezer was "clicking" intermittently, the compressor would not run, and temp was rising. This is a old, sturdy, and dependable 15 c/f unit in the garage. Been doing a heck of a job for 25 years or so.

Not totally unfamiliar with refrigeration and mechanics, I pulled out the unit and dove in... with reasonable care, of course. Fired up with a large 350 mf cap I temporarily pulled from another motor. Determined that the 88-108 mf cap might be bad, I replaced that. Could not resist the temptation to mess with the overload -- a Klixon MRA5933. It did need attention because the crimped wire connections were getting shaggy. Foolishly, I removed the bi-metal and it's stem, cleaned up contacts, and although the unit is now connected and is running properly, I do not trust the overload which absolutely must be way out of spec -- no way it could not be.

FYI, my Kill-a-Watt reveals start up current at nine (9) amps, and run amps at about three or so (3.0). Resistance between S and C is about 25 ohms, and between R and C about 5.5 ohms.

Other than any sage advice anyone cares to offer, what I REALLY need is a direct replacement for the MRA5993 overload. My research for that part reveals that I should have looked for it 15 years ago! Anybody... anyone... anywhere with a part number??? I'll be in your debt. Regardless, thanks for reading and your patience.
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richappy  
#2 Posted : Tuesday, March 6, 2012 3:08:16 AM(UTC)
richappy

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First, verify no compressor pin is shorted to ground. Next verify the klixon is still ok. This item is very reliable and it's kick open current probably between 25 and 35 amps.The trip open current, in my experience, does not deteriorate with time. However, if it now is opening often, eventually the contacts will fail. These klixons are carefully selected to protect each compressor, the implication is there is no universal replacement.
Let us know if you still want to replace it and the start device, universal replacements are available, but with reduced reliability/ safety.
Roger7500  
#3 Posted : Tuesday, March 6, 2012 6:37:20 PM(UTC)
Roger7500

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Thank you, Richappy. Measured with digital MM up to 20 meg range -- absolutely no pin is shorted to ground. Resistance: common to start is 19.2 ohms; common to run is 2.3; start to run is 21.1. Those seem good and well within spec. I already had disassembled the Klixon MRA 5933. Contacts were worn and pitted to a degree. Regardless, the bi-metal is no longer as flat as when it was new, and I have no idea of bi-metal tension or calibration of any sort. In my opinion, I have rendered the Klixon as useless. As it is now, temporarily in circuit, but not placed in correct proximity to the warm compressor housing, the freezer starts, runs, and stops appropriately. The Klixon might remain closed at 75 or 100 amps for all I know. Under these circumstances, I'd probably be just as unsafe/unprotected by removing the Klixon from the circuit altogether!

Note that the running compressor probably reaches an external temp of 60 degrees C., which is my wild guess. Another guess is that the initial problem involved a failing 88-108 mf start cap. Another possibility, is that various wires had corroded and frayed adjacent to their capacitor. Perhaps, it was a matter of pulling too much current through original 16 and 18 gauge wire which had been reduced to maybe a 22 gauge wire.

The only sensible thing, in my opinion, is to replace the overload. I know these things are "speced" in design -- that is a problem. One vendor, Carbonbrushes, claims to have Klixon MRA5933 in stock at $20+. I'm more inclined to go with a Supco protector in the OV30 to OV40 series. However, I' be real interested in whatever replacement you suggest.

Thanks again.
richappy  
#4 Posted : Tuesday, March 6, 2012 11:55:42 PM(UTC)
richappy

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My guess, you need a klixon with a kick out current between 25 and 35 amp. You can take your old klixon, put it in series with your oven, monitor the current and turn burners and bake elements on one by one till the klixon trips out, would verify exactly what you need. The click out temperature is not that critical.
Roger7500  
#5 Posted : Wednesday, March 7, 2012 12:03:33 PM(UTC)
Roger7500

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Thank you. I believe that I understand your approach. I'll do some more work, and we'll see how it goes.
richappy  
#6 Posted : Thursday, March 8, 2012 12:23:07 AM(UTC)
richappy

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For the old klixon, it appears to work fine as it trips open.You can allways use a heavy soldering iron and solder the frayed wires.
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