Bryant Gas furnace won't ingnite
I have a Bryant Plus 90 gas furnace. When themostat calls for heat it will sometimes blow cold air, or will shut itself down. The LED is giving a code 21 which the manual says it is a problem with the gas valve relay. Sometimes resetting will fix it, but the last few days it will not. Starter will glow, but when the click comes to start the gas, nothing comes out and the furnace shuts down with the 21 error code. Do I have to replace the control panel because of a bad relay switch, or is there another possibility? Pls post the full Model Number This is a Bryant Plus 90 - Model 350MAV It does look like you have a bad gas valve. Code-21 means gas valve did not open. Since you can hear the click, it appears the valve is getting its voltage...but mechanically (on the inside) is not opening. The failure is then, likely mechanical, and requires a valve replacement, but let's make sure that the gas valve coil is indeed receiving the 24V it should. B/C if 24V is not what the valve is getting, then it is not the component at fault. Here's what you need to do: 1- turn the thermostat to OFF 2- get yourself a voltmeter that is capable of reading 24VAC 3- notice in your furnace that there is a BLUE wire connected to one spade connector on the gas valve, and a GREEN wire connected to the other. 4- one of the meter leads must clip the spade connector on the gas valve where the BLUE wire ends; the other meter lead does the same on the other one (where the GREEN wire ends) 5- stay by the furnace so you can see what's happening. Have someone else have the t-stat call for heat 6- have a screw-driver on hand, grab it by the shaft (not the handle) 7- the inducer blower will kick-ON, the ignitor will glow...glue your eyes on the meter display when you hear the click 8- At the click you should read 24V on the meter...IF SO and no flames, the valve is bad. What the screw-driver for? when you hear that click and no flames are seen, gently tap the body of the gas valve. You only have about 2 seconds before the board shuts the furnace OFF on safety lockout. The tapping may un-stuck the valve and the burners ignite...this is for show and tell purposes only...the valve needs to be replaced anyway. 9- if the meter does not show a voltage reading, either a wire is lose (the Blue or the Green going back to terminals 2 and 8 on the 9-prong-plug hooked up on the board), OR the board is at fault (but from the sympthoms this is unlikely)
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