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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22679
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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Hi Billy, I have an american standard 90 furnace. I am getting

This answer was rated:

Hi Billy,
I have an american standard 90 furnace. I am getting the red blinking light in a three flash cluster. The blower is running but i am not getting any heat. It does not seem to be igniting. Could you help me please?

Is it the upper exhaust blower that is running?

Customer: replied 4 years ago.

No it is the main fan that blows the air through out the house.

Thank you,

So if you turn the power off and back on...thermostat set to heat...the exhaust fan does not run...and the main fan does? Then 3 flash error ocurrs?

Customer: replied 4 years ago.

That is correct

Do you have a voltmeter by chance?

Customer: replied 4 years ago.

Unfortunatly i do not but i can go borrow one if i need too. Would take me about 40 min. Should i go and get it?


It will confirm if power is going to the inducer motor but the motor is not running..

We have to decide betweeen circuit board or inducer motor.

Customer: replied 4 years ago.

Ok i will let you know when i am back with it.

And confirm the 3 blink pattern

Customer: replied 4 years ago.

Ok when i get back will it help if i send you a picture of the furnace with the covers off so you know what my set up looks like?

That would be beneficial.

Anything helps.


Customer: replied 4 years ago.

Ok have the volt meter and i will try to attach some pictures to this as well.


Unhook the wire connector to the inducer motor. Turn power off and put leads in the power supply wire to the motor...turn power on and thermostat to heat and turned up.

tell me if 115v ever flashes on meter

Customer: replied 4 years ago.

Nope. I get no reading at all.

Thank you.

just to confirm....can you tell me if there is 24v at this time terminal W to C on circuit board where thermostat wires attach?

Then we will be done..
Customer: replied 4 years ago.

Yep 24 exactly

Thank you.

The circuit board is bad. once 24v is present w to c then the inducer should get 115v output from the board. In this case (which is common) the inducer relay in the board is not engaging.

You will need to replace the circuit board.


Customer: replied 4 years ago.

Is that something i can do or should i have an expert come and do it? If i can do it where would i be able to get one and what is the cost? If i have to have someone else do it what should i be charged? (i realize those costs would just be approximate estemates)

Circuit board = around $175-$200

Labor/service call = $150

The boards are upgrade and have changed. Some require retrofit and get get a bit complicated.

I never know ones comfort level or aptitude for this can of work so I am afraid I must leave that choice to you.

I really wish you well


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