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Old 10-03-2022, 02:40 PM   #1
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Suburban SF35 Board Replacement Issue

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
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Old 10-03-2022, 03:06 PM   #2
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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
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Old 10-03-2022, 06:07 PM   #3
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Does this eliminate the time delay relay that is pictured?
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Old 10-03-2022, 06:08 PM   #4
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Quote:
Originally Posted by bounderdude View Post
Does this eliminate the time delay relay that is pictured?
YES as shown in info in LINK posted





New wiring diagram provided also

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Old 10-03-2022, 06:33 PM   #5
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Yep I saw that right before I came back and saw your reply. Thanks a lot for the help I went ahead and purchased the wiring kit!

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Originally Posted by Old-Biscuit View Post
YES as shown in info in LINK posted





New wiring diagram provided also

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Old 10-11-2022, 03:50 PM   #6
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So my SF 35 has no valve switch. Do I just ignore these steps or am I going to have issues?

Quote:
Originally Posted by Old-Biscuit View Post
YES as shown in info in LINK posted





New wiring diagram provided also

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