Bypassing a Furnace Control Board with a 90-340 Relay to get Blower Running

Not DIY advice. This is just myself diagnosing a control board for a furnace that would not let the blower motor run. I bypassed the blower motor fan part of the faulty control board with a all purpose 90-340 relay for a temporary fix to get the cooling going.

[@richlikeg3722]

This video saved a customer from the heat of Texas. Her motherboard burnt up and I had to bypass it. I had a 90-340 in the truck and I hooked it all up. She was cooling within the next hour. Get it done fellas, I never used on before.

[@AaronPowellvox]

I like that method. I usually straight wire the fan until I can get them a new board but your method allows for the fan to run with everything else like normal until you can get a new board.

[@jaykeller1]

So far this is the best video I have seen for peforming this temperary fix.

[@TheRicardo7500]

This is an amazing video, straight to the point, you made it look easy. Thank you so much!

[@wilmercruz3889]

I love your videos man, I've been working as maintenance tech for a couple of years and your content has helped me a lot.

[@ApartmentMaintenancePro]

Thank you wilmer I appreciate it :_

[@benjamintimmins1656]

You're a hell of a tech bro! I've never used a relay just a contactor or actually what I like to do it hook the fan speed up to the door switch....but good job. Now I know how to do it!

[@ApartmentMaintenancePro]

Thanks Benjamin I appreciate that 👍

[@gotchaplumber]

Great video!

[@user-mb5cr1ts8g]

Oh mugid was about time someone did it so simple

[@bawipengcin8591]

Thanks for sharing and teaching

[@MsFishingdog]

Good job.

[@esbonwordenjr6069]

Just for future as long as you dont have an ecm fan motor you can take your heat wire off and put it on the EAC terminal which will also do the same thing without having to add a whole seperate relay because the eac is electric air cleaner which has its own relay to turn on when the furnace turns on.... ive done it multiple times till i get a new ifc board.... or you can unsolder the relay from the board and solder on a new one if u got it which most people wouldnt so just pull the wire off and put it on eac terminal which is a 120 terminal...... let me know if you have tried this before

[@markharris9647]

I'm a new tech I will try that can you make a video for me

[@Niafi11]

I just need to know if i can use 90380 instead of that 90340. Its all i got and its the Weekend. I guess im gonna have to wait til Monday

[@BridgeWater94]

Question. How are you able to work on hvac equipment and get supplies? I’m doing maintenance right now and they want me to work on some hvac equipment. The problem I’m running into is I can’t get into supply houses for equipment. What can I do to get into supply houses assuming your able to? Do you have a mechanical contractors liscence for hvac? I’m stuck on how to go about this

[@ApartmentMaintenancePro]

My company has an account with Johnstone so I can walk in there . We also use a mechanical contractor to get us supplies

[@viper22304]

thanks for sharing. awesome work. Question: if you were to use the low speed (heating), where would you connect it to the relay?

[@ApartmentMaintenancePro]

Remove your speed wire hooked up and place the low speed wire in its place. Ensure the speed wires are insulated or strapped up

[@jorgedelaossa9899]

Thank you

[@mikeo9049]

If you don't mind me asking, what do you record your videos with? Keep up the great work.

[@ApartmentMaintenancePro]

Most of the time its an iphone 14 pro. When I'm at home, I use a nikon z6ii with various lenses.

[@cwilliams6884]

if you can find the relay that goes on the board that's a pretty easy board fix

[@adielguillermo]

How can bypass if is the heat?

[@viper22304]

thinking the same question.

[@mohammadalizada7715]

You said that the board is bad so why still the natural works there? 🤔

[@BigWilldeClue83]

Fan relay is bad on the board, so once it calls for as the relay is the only thing that doesn’t close to complete the circuit.

[@5251168]

In that application why not just use a spst 90290 or other rectangluar fan relay, the other circuits are not being utilized, and eliminates the thunk noise people will complain about

[@ApartmentMaintenancePro]

I used what the building had, which was the relay that can bypass almost anything. I've also used 2 pole contactors in a pinch before for the same thing. It's in a common area in an apt building.

[@abdullah_q8171]

Bypass you dont use the board?

[@benjamintimmins1656]

The relay on the board is stuck open...this is a better way than hooking the fan up to door switch where it runs all the time...

[@esbonwordenjr6069]

Just take the heat wire off and put it on the eac terminal and bam your done till you get a new board because no one usually has an electric air cleaner hooked up so use that terminal.... it will just make the fan turn on immediately when a call for heat or cooling comes in.... just as long as you dont have an ecm motor but even if you did no relay would work anyway

[@bobbywanger8123]

👍👍👍👍👍🔥🔥🔥🪛🪛🪛🪛🪛

[@ApartmentMaintenance]

I keep one of those relays on hand for an emergency situation just like in your case. I put it in place of the goodman AWUF blower board if I dont have a board on hand for some reason. Its funny how some guys are amazed when they see something like this done cuz all they know is swap out part for part. But if you understand how the system & the relays work you can make it happen. Nice job bro! 🛠️👍

[@ApartmentMaintenancePro]

Thanks man ! Hope all is well with you. I've used contactors before to bypass boards in a pinch 😆 there's always a way to make it work

[@ApartmentMaintenance]

@@ApartmentMaintenancePro Sure is. All good with me. Waiting for the weather to cool off some to catch a break & get some other things done around the property. It's just been non stop all summer.

[@jugears1081]

Thanks