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bounderdude · 10-03-2022, 01:40 PM

Hey guys. Not to long ago I found out the furnace would not do anything at all (no fan no clicking no nothing) when the thermostat was turned on. I’ve bought a replacement board(which is an SF35 replacement board and actually for all suburban furnaces/hot water heaters) which has a “PWR” and “BLO” tab that have to be hooked up when the other board didn’t. Can you guys help me hook these up?
Thanks for the help!

Here is a link to the exact board I bought. In the reviews/Q&A people explain they have to hook those tabs up when the old board didn’t have them.
Suburban SB521099 3G Furnace Fan Control Board https://a.co/d/1bKgAnL

Old-Biscuit · 10-03-2022, 02:06 PM

YOUR SF35 model uses a Timed Delay Relay (relay in 2nd picture)
It is probably your problem
DC goes to the relay (and to thermostat)
When thermostat closes the DC comes back to relay thru coil to ground
Coil heating up allows DC to Fan

Bad relay...no fan ---no fan nothing else gets DC

The Circuit Board you purchased is for newer SF models that do not have the Relay.....it'sfunction has been incorporated onto the circuit board

BUT all is not lost.....there is a 'wiring kit' with instructions available to swap from the TDR to Pwr/Blo

https://pdxrvwholesale.com/products/...ing-kit-520832

Replacement/new style TDR available but costs $40-$50 depending on vendor
Suburban Furnace Time Delay Relay 48000