posted on 10/13/2007
I have a Trane 80XL and the light on it is giving the '3 flash' error indicating a draft pressure problem. Any help with troubleshooting? So far I turned off the power to the furnace, reset the gas ignitor switch, turned the power back on, turned the heat on at the thermostat and then I get the 3 flashes. The blower motor won't seem to kick in automatically. I can turn it on and it runs fine but it won't kick in on it's own. I checked the tubing to the fan - it's clean and clear. the furnance is only from 2002. Vents are clear, filters are clear... If I turn off the power to the furnance and turn the blower motor switch off, the light will flash normal (but the heat won't kick in) until I flip the blower motor swtich to on, then it reverts to the 3 flashing mode. any suggestions? Thanks!
replied on 10/14/2007
When you say the blower switch are you talking about the fan which delvilers air to the duct work or are you talking about the inducer fan? - I don't know of a swich for the inducer. but I think you have a problem with the inducer fan - first on a call for heat the inducer should come on - if it does't check for 120V to the inducer fan. if you have 120V going to the inducer and the inducer is on check for 24V to the pressure switch. if you have 24V to the switch but the switch is not closing (switch would give you the same code as if the inducer is not coming on) check the port at the fan end (this is a neg pressure switch) these ports sometimes plug up. if this is the case it should be cleaned and checked by a tec. if you do have 120V to the inducer and it isn't working . please note that this inducer is a neg system and 12" from the inducer the venting will work the same way a old furnace would work, heat will carry the products of combustion thru the vent (is sized properly, the only time this fan pushes air is at start up will the air thru the heat exchanger is cold. so don't assume the fan will push the products of combustion away. let know - Brian
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