View single post by The Seven
 Posted: Mon Apr 18th, 2005 09:21 am
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The Seven

 

Joined: Tue Mar 29th, 2005
Location: Canada
Posts: 181
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iceman wrote:
Looks like you are right, in the July 1999 version, the relay looks to be of a higher current handling capacity than the 1996 unit pictured above.


I would concur with you and Denrayer. The 1996 is much worse than the 1999.

My comments to these control boards:
1) Most defrost heater takes about 3A to 4A at 120V.
2) Most compressor-motor during normal running takes a full-load current of 2A to 3A at 120V.
3)At start, the motor could take a lock-rotor current (LRA) which is 6 to 10 times the full-load current (say, LRA = 12A to 30A).
4) The lock-rotor current is the most damaging current which tends to melt the contacts in the miniture relay. The contacts could fuse together to form a permanent ON circuit. Or they could melt apart to form a permanent OFF circuit.
5) The copper tracks on the circuit board may not able to carry the heater current and motor current. These copper tracks may be heated up and cause some melted soldering points at the relay. This will cause "intermittent" fault.

See the attached JPG photo. Melted soldering points at COM (compressor) and DH (defrost heater)

The under-current rating "relay" and "copper tracks" are the two main failure causes of these boards.



Attachment: FaultyCircuitBoard.jpg (Downloaded 313 times)

Last edited on Mon Apr 18th, 2005 09:27 am by The Seven



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The Seven