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starlitecafe · Oct 27, 2009, 09:16 AM

My xc90 (the furnace) has sporadically worked on and off for the past couple of years. Right now it's not working at all.. there is 24v at W but the inducer isn't coming on. The error code tells me there is a pressure switch issue but the green led flashes slowly indicating there is no call for heat. If I still had hair, I'd be pulling it out. Help.

hvac1000 · Oct 27, 2009, 11:52 AM

Turn off main furnace power then jump R and W on the low voltage strip in the furnace then reactivate main power and post back with results.

starlitecafe · Oct 27, 2009, 02:03 PM

Originally Posted by hvac1000

Turn off main furnace power then jump R and W on the low voltage strip in the furnace then reactivate main power and post back with results.

There is 24v back from the stat to W but the green led flashes slowly indicating no call for heat.

starlitecafe · Oct 27, 2009, 02:06 PM

Originally Posted by starlitecafe

There is 24v back from the stat to W but the green led flashes slowly indicating no call for heat.

I had disconnected and then reconnected power and even waited 60 minuets to clear the memory. I keep getting the same error code (pressure switches) but even when I bipass them, no dice.

hvac1000 · Oct 27, 2009, 02:08 PM

I do not care if 24 volts is coming back from the thermostat. I did not ask you that question. I told you to do exactly this for a reason.

Turn off main furnace power then jump R and W on the low voltage strip in the furnace then reactivate main power and post back with results.

starlitecafe · Oct 27, 2009, 02:18 PM

Originally Posted by hvac1000

I do not care if 24 volts is coming back from the thermostat. I did not ask you that question. I told you to do exactly this for a reason.

Turn off main furnace power then jump R and W on the low voltage strip in the furnace then reactivate main power and post back with results.

Ok. Upon re energizing I had 2 error codes. One indicated pressure switch problem and the other indicated an inducer communication fault.

starlitecafe · Oct 27, 2009, 03:14 PM

Originally Posted by starlitecafe

Ok. Upon re energizing I had 2 error codes. One indicated pressure switch problem and the other indicated an inducer communication fault.

My mistake. It is an xv90.

hvac1000 · Oct 27, 2009, 03:52 PM

The next step is to check the pressure switch and inducer motor for proper operation.

starlitecafe · Oct 27, 2009, 04:41 PM

Originally Posted by hvac1000

The next step is to check the pressure switch and inducer motor for proper operation.

I removed the hoses and blew into the pressure switches and they appeared to function properly. I put 110v directly on the inducer motor (high speed) and it worked properly. While it was running mysteriously on it's own, which it has done from time to time, the bearing temperature maintained at 165f which seemed normal as the burners were on at the time.

starlitecafe · Oct 28, 2009, 01:23 PM

Originally Posted by starlitecafe

I removed the hoses and blew into the pressure switches and they appeared to function properly. I put 110v directly on the inducer motor (high speed) and it worked properly. While it was running mysteriously on it's own, which it has done from time to time, the bearing temperature maintained at 165f which seemed normal as the burners were on at the time.

Perhaps someone can tell me if the pressure switches should be no or nc upon a call for heat. Also, does the inducer motor, after a proper time out, supposed to come on first, creating pressure(or lack there of) for the switches, when heat is called for.