# My furnace board relay clicks off/on...



## mhvac (22 d ago)

Hey everyone, been having some issue with my furnace lately. Furnace still works fine and heats the home but has an issue with the board relay for the fan clicking OFF and back ON right way.

Basically this is what happens:
-Flame and the fan turn ON to heat the home fine
-When the home is heated to my thermostat temp, the flame turns OFF, fan stay ON for a few minutes to cool off the furnace as far as I understand and this is normal. This is when I can hear the fan relay on the board click OFF and right back ON in a split second. It does this OFF/ON a few times in the 2 3 minutes the fan is cooling off the furnace.

Wondering what's going on here?
Board going bad?
Or maybe just a fan relay going bad on the board?
Or could it be my Ecobee thermostat having issues actually and switching the fan off and on?

Thanks for any help I can get


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## mhvac (22 d ago)

*Got an update for anyone reading in the future, I figure it out 🙂*

I did some testing, and I found out that the OFF/ON thing always happens at exactly 30 seconds into the blower fan delay timer... exactly 30 seconds every time, found that add so did more testing...

So the blower relay has 2 wires on is going to the blower fan, one says HEAT one COOL. I decided to unplug COOL so only the HEAT blower fan wire is connected to the relay and guess what...

When the blower fan timer delay starts, first 30 seconds the HEAT blower wires has power going to the fan, then the board turns OFF HEAT wire at 30 seconds, and switches to the COOL blower fan wire, which is now unplugged so by blower completely turned off at 30 second. Then at 90 second mark I can hear the board click / turn OFF the relay again which is the COOL blower wire.

So for whatever reason this boards blower fan delay works like this: First 0-30 seconds uses HEAT blower fan wire, and then 30-90 seconds of the blower fan delay it uses the COOL fan wire/terminal to finish off the blower fan delay...

I have no clue if this is a faulty board or this is now it was mean to be originally but at least now I know what is going on and why I had the OFF/ON clicking from the board at 30 second into the blower fan delay timer.

Is this how this should work? No clue why its switching the blower from HEAT to COOL after 30 seconds

Anyways hopefully this help someone in the future if they run into the same weird annoying relay clicking 30 seconds into the blower fan delay...


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## upyourszz911 (17 d ago)

Look at your thermostat manual. it should have all kinds of adjustments. You can program how long (used to be dip switches) you want blower fan to run after heat or cool stops. usually 30 45 60 even 90 seconds. I believe some even have 0. Bad relay can be checked with multi meter, place on ohms and check for continuity. 30 seconds is a timed relay.


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## mhvac (22 d ago)

Had more talk on this in another forum for anyone interested in the future...

_So basically my Goodman board during "blower fan delay", does the first 30 seconds of the fan in HEAT mode, then the relay CLICKS and switches to the COOL blower for the rest 60 seconds... Thats the annoying click I hear that I was complaint about... Thing to note here, it happens exactly at 30 seconds every time which is what made me think it might be normal... _

Only thing the jury is still out on is why after almost 2 decades of living here I only NOW hear this HEAT blower --switch--> COOL blower after 30 seconds

PS board (b18099-13) has a 90, 120 or 150 sec fan delay setting, set but a jumper pin. Never messed with it before until this thread...


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## Ben.Wolfinger (22 d ago)

mhvac said:


> *Got an update for anyone reading in the future, I figure it out 🙂*
> 
> I did some testing, and I found out that the OFF/ON thing always happens at exactly 30 seconds into the blower fan delay timer... exactly 30 seconds every time, found that add so did more testing...
> 
> ...


The heat and cool labels on the board are simply for different fan speeds. Black wire to cool is high speed for air conditioning so when your thermostat is set to AC the blower runs at high speed. Generally speaking, you want the Red wire (Low Speed) for heat because slower moving air is generally warmer than fast moving air. Unplugging the black wire from cool should not have stopped the clicking because the thermostat set to heat should never have been looking at the black COOL wire on the board. The fact that this worked for you is indicative of a faulty control board.


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