White Rodgers 21V51U-843 Universal Two-stage HSI Integrated Furnace Control Kit Schéma

The 50V51-843 has only one serviceable part –an automotive 

type fuse, which protects the low voltage transformer from dam-

age if the output is short-circuited. If the fuse has opened up, 

remove whatever caused the short circuit and replace the fuse 

with only a 3 amp automotive type fuse. If the fuse is not the 

cause of the control’s problem, replace the entire 50V51-843

control. There are no other user serviceable parts. 
Following installation or replacement, follow appliance manu-

facturer’s recommended installation or service instructions to

insure proper operation.

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