# Fan relay bypass...



## jreyno24 (Dec 5, 2010)

Hi,

A while back my Honeywell ST9101A control board went bad. The fan relay stopped working. He rigged the wiring so the blower fan ran constantly. Rather than spend the $400 he wanted for a new board, I went ahead and replaced it with a ST9120U. Moved all of the wires over and the blower fired right up. While I was moving the connections over, I notice there was no wire connected to the "COOL" terminal on my old board. There was also two terminals that look like they were disconnected from the board and then taped together with electrical tape. So a few questions ... 

1) Is is ok to not have a COOL connection to the board? Is does run both my heating and cooling. The A/C still works.

2) I have no idea about those two wires taped together. They have terminal connections on them, so I assume they were connected to the board at one time.

3) The blower still runs constantly. What did my technician do to bypass the fan relay?

I can provide pics if that would help.

Thank you!


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## yuri (Nov 29, 2008)

Pics would help. Post the make and model and serial # of furnace also.


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## jreyno24 (Dec 5, 2010)

Thanks .. It's a Rheem Criterion RGDG-075AUER. The two wires with terminal connections taped together are coming through the blower. Post pics in a bit.


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## jreyno24 (Dec 5, 2010)




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## yuri (Nov 29, 2008)

What the heck is going on there????
Everything needs to work off the original Rheem yellow board!!!
You may have a bomb sitting there with no proper flame failure circuit etc. Only OEM boards will work and meet the code etc.


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## jreyno24 (Dec 5, 2010)

The original board was a Honeywell. No Rheem yellowboard.


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## yuri (Nov 29, 2008)

I can see it behind your board in the pic. Sits inside that plastic box. Somebody is trying to retrofit your unit and that is not allowed.


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## jreyno24 (Dec 5, 2010)

yuri said:


> I can see it behind your board in the pic. Sits inside that plastic box. Somebody is trying to retrofit your unit and that is not allowed.


The board in the back is the bad Honeywell ST9101 that is being replaced. The board is no longer produced. It's the board that came with the house and that passed code. My neighbor also has the same board with the same system.


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## yuri (Nov 29, 2008)

Suit yourself. The original Rheem board is still inside the electrical box and should be used. The furnace was AGA and UL certified for the Rheem board only. Universal ones have a large disclaimer that they may not work with all models properly. I won't use them. The same tech altered your neightbors furnace and it was not passed by the proper authorities. I am sure your house ins. may be void if there is a fire/explosion and they find out about that board.


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## jreyno24 (Dec 5, 2010)




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## Jackofall1 (Dec 5, 2010)

jreyno24 said:


> Hi,
> 
> A while back my Honeywell ST9101A control board went bad. The fan relay stopped working. He rigged the wiring so the blower fan ran constantly. Rather than spend the $400 he wanted for a new board, I went ahead and replaced it with a ST9120U. Moved all of the wires over and the blower fired right up. While I was moving the connections over, I notice there was no wire connected to the "COOL" terminal on my old board. There was also two terminals that look like they were disconnected from the board and then taped together with electrical tape. So a few questions ...
> 
> ...


Both heat and cool off the same relay, see no problem with that. Usually for different fan speeds.

Trace the wires that are taped together back to where they originate, my guess is they come from the motor. They have stake ons but they don't look like the type that would go on a board (no insulation on them).

My guess is the motor was wired direct to line and neutral, the wires taped together are from the motor for differenct speeds. Again just a guess but thats all we can do at this point.

But like the guy says, that board doesn't belong on that furnace and this could present problems and expose yourself and family to a very dangerous situation. I did search and found that board quite easily as well.


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## yuri (Nov 29, 2008)

OKAY, I apologize, all the Rheems I see in Canada have a genuine Rheem board and I was concerned about your safety if a hacker substituted a universal in. I would get the board from Rheem and they should have retrofit cables and instructions in the box for all the wiring. You may be getting some backfeed and blowing relays with the way it is now. There is a specific purge cycle timing and flame failure response timing where the universal board may not match the Rheem specs and thats where the danger and liability issues arise. Safety comes first not saving $$.


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## jreyno24 (Dec 5, 2010)

What is the model of the correct board that is supposed to go in here?


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## Jackofall1 (Dec 5, 2010)

jreyno24 said:


> What is the model of the correct board that is supposed to go in here?


Honeywell ST9101A is this not the board that is mounted in the backgound.


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## yuri (Nov 29, 2008)

Depending on your electricity rate it may be costing you $1 a day to run that fan all the time. Better to get the proper Rheem board. New furnaces have energy saving ECM motors that only use 80 watts on low speed. One of our buds homeairdirect dot com may be able to hook you up with the proper board. Needs the complete furnace model and serial # and Honeywell info from the original board.


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## jreyno24 (Dec 5, 2010)

Thanks everyone..


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## yuri (Nov 29, 2008)

Check my previous post for added info.


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