trane xr80, no heat, nothing, 3 flashes on board

Old 11-02-14, 09:24 PM
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trane xr80, no heat, nothing, 3 flashes on board

so 3 flashes is the pressure switch, I checked the tube and into the chamber there is no blockage, testing the switch itself when I blow into tube I have a broken circuit, when I suck air from the tube my ohm meter then goes to 0 so I'm not sure if that is how the pressure switch is supposed to work, does anybody knows how to really determine if the switch is bad? However, I just connected the switch leads to close the circuit to test that aspect and still get the same flashing 3 times. This is a new board installed this summer and A/C works ok. by directly connecting the switch leads to eliminate if the problem is in the switch itself, could it be that the board itself is faulty? or can there be something else besides the switch itself to cause the 3 flashing lights? I have googled a fair amount but have not seen anything specific
Old 11-03-14, 04:16 AM
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The pressure switch works on vacuum, sounds like the switch is OK. Trace the wires from the switch and make sure the connections are good.
Old 11-03-14, 06:37 AM
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A 3 flash code points to a problem with the pressure switch, inducer motor or vent pipe.

Here is a link to the installation guide for your unit:

Make sure the hose from the pressure switch is clear from end to end and has no rips or tears. Check the nipple where the hose attaches to make sure there is no crud blocking the small hole in it. You can use an opened paper clip or small drill bit to ream it out. Make sure it is clear all the way through.
Check the vent pipe to make sure there is nothing blocking it such as a bird's nest, bee hive, dead bird or other debris inside.

When you set the thermostat to heat does the inducer motor start up right away and run at normal speed?

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