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Trane XE 80 Fan keeps running

PostPosted: Thu Nov 17, 2016 10:56 am
by homebody
Have an 17 year old Trane XE 80 and a few days ago had a professional HVAC company come out and do a winter tune up. Unit was running fine - no problems before their visit.

The next day after they left, the heat came on and the fan will not stop blowing after heating up to the temp indicated on the thermostat. It worked properly for about 14 hrs after they left - but then this fan issue occurred. The unit will not turn off at the thermostat and the only way to get the fan to stop is to go up in the attic and turn off the power switch to the unit.

After about 3 hours of it being off - turn it back on and it will then work properly for about 24 hours - and then the fan issue returns. Have to go back up into the attic and turn it off again.

It is Model # is TUD080C936H4. Trouble code is 5 flashes which according to the manual - "flame sensed with gas valve off".

The tech who tuned it up appeared to remove a whole bunch of wires and said he was testing to see if everything was in proper range. He said the unit was in remarkably good condition for it's age and that the burners looked nearly new. I got the distinct impression they wanted to sell me more than just a winter tune up.

Could he have put any wires back incorrectly or done anything that would make this happen? Is it reasonable to ask them to come out and check it at no additional cost to me ? I can pull the cover off the unit and wonder if there is anything I should look for where they might have screwed up.

Tks.

- Trane XE 80 Fan keeps running

PostPosted: Sat Nov 19, 2016 2:13 pm
by Freon
I would definitely call them back before you do anything. As it stands now, their hands were the last to touch your furnace. Sadly I think the tech messed things up. Tell the company exactly what you posted here and make sure their return visit is at no charge before authorizing them to come.

If they don't find the answe, post back here. You will need to look at the wiring schematic that's usually glued on the inside of the blower (fan) door and verify each connection. It is possible, if you have a "smart valve" that the circuit board on that valve is bad. But first get the company back.

- Trane XE 80 Fan keeps running

PostPosted: Tue Nov 22, 2016 12:36 pm
by homebody
Thank you for the reply. Trying to get the company back out. Been doing some research online and someone had suggested it could be the fan relay switch sticking. To be clear about what is happening - the fan will keep running after it heats up to the temp on the thermostat, but if I shut off the power to the unit for a few hours and then turn it back on - it will function properly for about 24-48 hours and then the running fan issue starts again.

Where would the fan relay be located or this smart valve that you mentioned.. or are they one in the same? Based on the cold weather we are having, it is likely that if the company does come back out to check it... that it will be working at the time they come (since I have to shut it down and turn it back on to heat) - otherwise the fan would have to be running continually until they get here (days) and that would likely burn it out.

Thank you in advance.

- Trane XE 80 Fan keeps running

PostPosted: Wed Nov 23, 2016 10:18 am
by Silverjwj
It sounds like somethings wired wrong causing things to happen out of sequence. Id make them fix it.

- Trane XE 80 Fan keeps running

PostPosted: Wed Nov 23, 2016 2:14 pm
by homebody
Had the company come back out - different tech this time. Explained what was happening and he looked it over and said that there is now an intermittent short in the control board. According to him the unit will work properly until the board heats up causing the short - thereby triggering the false reading from the flame sensor.

If we turn the power to the unit off for a few hours and then turn it back on, it will work for a period of time and then this fan issue starts happening. Luckily it was happening when he was here so he got to see the error code.

It is highly suspect to me that this would happen after a routine checkup. They did come out again at no charge to check it. $448.00 fix for the board is what they want and that is their "preferred" customer price.

If there is an HVAC pro reading this who can respond - does their diagnosis sound reasonable? Tks in advance.

- Trane XE 80 Fan keeps running

PostPosted: Wed Nov 23, 2016 4:24 pm
by Freon
The control board for the furnace will be inside the furnace, not on the valve. I would turn off the power and carefully remove the furnace control board making very careful notes about wire connections. You'll need the notes to reconnect it. Carefully look for any cold solder joints or cracked copper leads/traces on the circuit board. If the intermitent operation is a result of thermal expansion/contraction then there may well be a tiny crack in a solder joint or copper trace on the circuit board. The relay is not stuck but the power to it is not being switched off for some reason.


Also get any data off the board and go shopping. Sometimes you can find a new one at a much more reasonable price.

- Trane XE 80 Fan keeps running

PostPosted: Thu Nov 24, 2016 10:18 am
by homebody
Thank you for the replies. Found the number on my circuit board (CNT2182 50A50-473) and went looking for a replacement and there appear to be a few other boards that can replace it. However they are not the same size physically as the previous board and they also look to have different connector layouts. The one that is coming up the most is part # 50A55-486.

Would this be an easy basic wire switch over from the old control board to this new one? Any issues with it being smaller in size and attaching it to the furnace?

Thank you in advance.

- Trane XE 80 Fan keeps running

PostPosted: Thu Nov 24, 2016 2:54 pm
by Freon
Google the 50A55-486 and see if it definitely says it is a replacement for your board. That sounds like a White Rogers number and they do make many control boards. If it's a direct replacement, download the instalation manual and read it comparing their connections with the connections on your old board. The connection terminals should be similarly labeled. If you can understand how to wire the new board, then you can get it.


As for size, that's not important provided you can fine one or two screws to fasten it securely to the furnace. You don't want the bare PCB to be able to contact the metal furnace frame. But it doesn't have to look pretty, it only has to function.

- Trane XE 80 Fan keeps running

PostPosted: Thu Nov 24, 2016 6:49 pm
by homebody
Thank you Freon. Appreciate the help. Will locate a board and give it go. Tks