Electronics > Repair

Seeking recommendations on replacement compressor relay for dehumidifier


door king:
Howdy all,

I just had a dehumidifier punk out on me and I have pinpointed the problem to the compressor relay.  The culprit is a Sanyou SFK-112DM: 

I was hoping I could get some recommendations on a replacement that will hopefully be of higher quality/reliability.  Of particular appeal would be a relay that will not fail in the "closed" state.  The original relay failed in the closed state, the contacts having apparently welded themselves together. (It's a normally-open relay.)  The other day I noticed that the compressor was running, but the fan wasn't.  After briefly fiddling with it I discovered that the compressor would run continuously, even when the machine was off (soft switch).  The only way to stop the compressor was to unplug it, so a replacement relay that is guaranteed to go into the "open" state if it fails would assure a little more safety.  Not sure if that's a thing. 

I found a few options at DigiKey: 
TE Connectivity PCF-112D2M,000 -- https://www.digikey.com/en/products/detail/te-connectivity-potter-brumfield-relays/PCF-112D2M-000/1128659
CIT J120D1AS12VDC -- https://www.digikey.com/en/products/detail/cit-relay-and-switch/J120D1AS12VDC/12503177

Also these, but they're not regular stock: 
Panasonic ALF1T12 -- https://www.digikey.com/en/products/detail/panasonic-electric-works/ALF1T12/645563
Omron G4A-1A-E DC12 -- https://www.digikey.com/en/products/detail/omron-electronics-inc-emc-div/G4A-1A-E-DC12/202598
CIT J120D1AC12VDC -- https://www.digikey.com/en/products/detail/cit-relay-and-switch/J120D1AC12VDC/14002110 (NOT SEALED)

Any comments on the quality of the above manufacturers?

Also, is there a designation or name for this 'form factor'?  Comparing them they all have the same pin layout, but I couldn't find any term that designates this style.  If I knew what it was called it would make it easier to search for further options. 

Does anyone know if there are any drop-in solid-state equivalents? 
(It will probably have to run fairly cool since the board is in a pretty tight enclosure.  Not much room for a heat sink and I wouldn't want to mess with that anyway. )

Thanks in advance,

I would just put in the one you have listed first and call it fixed.  The contact welding issue was either an issue with the quality of the OEM relay or the compressor drawing excessive current at startup.  I don't know of any mechanical relay that would 'guarantee' that it couldn't be welded and SSRs have their own issues.

How sure are you that the problem is the relay?  The most common problem for continuous running is loss of freon.  Is the unit still under warranty?  If so, just return.

door king:

--- Quote from: jpanhalt on June 19, 2021, 07:40:52 pm ---How sure are you that the problem is the relay?  The most common problem for continuous running is loss of freon.  Is the unit still under warranty?  If so, just return.

--- End quote ---
Low refrigerant would cause continuous running only if the controller is demanding dehumidification.  The compressor in my machine runs continuously independently of where the shutoff threshold is set, or even if the unit is turned off.  The fan behaves itself:  If I set the threshold below the room humidity, it will kick on, and if I set the threshold above the room humidity it turns off. 

With the machine unplugged and the wires on the secondary terminals removed (hot from plug & output to compressor), I read zero ohms across the secondary pins. 
With the machine plugged in, hot from plug reconnected to relay, and compressor wire still disconnected I get 120V at pin for the compressor, even when the machine is turned off. 
If it was the controller forcing the relay closed under the wrong conditions, the relay still ought to release and read OL when the machine is unplugged. 

She's long out of warranty, unfortunately. 


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