i found my carrier 58pha090-016 furnace had no flame with the igniter on, and exhaust fan running, etc. it kept trying 3 times then stop. i reset the power switch of the whole system, the same cycle repeated. of course, i confirmed the main gas valve to the furnace from house was open, and the heater near by working fine. i testeded the power cable to the gas valve (White Rodgers modle 36j24-618, 1 stage, 24V) had 27V after the igniter on, and no voltage when the system off, that meant the control board and limit switches etc were all functional. More likely the bad gas valve. I could replace the gas valve. however, i am not sure if the 27V output from the control board was the root causing the damage to the gas valve from the first place, or it's still a acceptable range? Ichecked the gas valve manual there's no range in its specifications. i checked the output from the transformer (with label of 24V output) the reading was 27V. some people online said the transformer range could be from from 24V to 28V. if anyone has any experience about this, pleait's greatly appreciated for your advises. thanks in advance!
Is the 24v transformer output ~27v normal
furnacegashvactransformervalve
Best Answer
It does sound like the valve and/or solenoid is bad. You measured 27 volts, but that's only about 10% above the specified value, which is pretty close for a random transformer. The voltage will likely sag as you approach the rated current draw from the transformer, but even if it doesn't that's pretty close.