Carrier 50TJ low voltage Issue

[coolitdown]

Good evening everyone. Need a little direction. We have a 6-7 year old, 5 ton (carrier 50TJ) package unit one heat, one cool unit that has recently had the blower motor replaced. End of last week service tech replaced a thermostat and time delay relay. I went by today and found blower motor not shutting down after satisfied thermostat. Found an additional relay with N.O contacts that were stuck closed. Replaced and tested operation. Found unit doing same thing due to voltage being supplied by Heating wire from thermostat. Disconnected heating wire and fan shut down. Removed thermostat from wall and went back up for testing. Phsically jump wires to get into cooling and then discounnected. Fan stayed running and W (heating wiring) showing 20-22 volts with thermostat pulled from wall. (FYI Red from xfrmr has 26volts). Not sure why, perhaps shorted with another low volt wire, but unable to locate. Did get cooling running today and was fine. Called customer who said it was running ok all day. Asked him to shut off and restart with thermostat and call me back. He called back and said system never started back up placing it on cool at 65 degrees. Tried just blower fan operation - nothing. Think tripped the transformer? What do you think?

[just_opinion]

Good evening everyone. Need a little direction. We have a 6-7 year old, 5 ton (carrier 50TJ) package unit one heat, one cool unit that has recently had the blower motor replaced. End of last week service tech replaced a thermostat and time delay relay. I went by today and found blower motor not shutting down after satisfied thermostat. Found an additional relay with N.O contacts that were stuck closed. Replaced and tested operation. Found unit doing same thing due to voltage being supplied by Heating wire from thermostat. Disconnected heating wire and fan shut down. Removed thermostat from wall and went back up for testing. Phsically jump wires to get into cooling and then discounnected. Fan stayed running and W (heating wiring) showing 20-22 volts with thermostat pulled from wall. (FYI Red from xfrmr has 26volts). Not sure why, perhaps shorted with another low volt wire, but unable to locate. Did get cooling running today and was fine. Called customer who said it was running ok all day. Asked him to shut off and restart with thermostat and call me back. He called back and said system never started back up placing it on cool at 65 degrees. Tried just blower fan operation - nothing. Think tripped the transformer? What do you think?

I think you definitely need a service tech. Sorry but no DIY

[dandyme]

and just what did the tech replace the thermostat with???

[timebuilder]

Good evening everyone. Need a little direction. We have a 6-7 year old, 5 ton (carrier 50TJ) package unit one heat, one cool unit that has recently had the blower motor replaced. End of last week service tech replaced a thermostat and time delay relay. I went by today and found blower motor not shutting down after satisfied thermostat. Found an additional relay with N.O contacts that were stuck closed. Replaced and tested operation. Found unit doing same thing due to voltage being supplied by Heating wire from thermostat. Disconnected heating wire and fan shut down. Removed thermostat from wall and went back up for testing. Phsically jump wires to get into cooling and then discounnected. Fan stayed running and W (heating wiring) showing 20-22 volts with thermostat pulled from wall. (FYI Red from xfrmr has 26volts). Not sure why, perhaps shorted with another low volt wire, but unable to locate. Did get cooling running today and was fine. Called customer who said it was running ok all day. Asked him to shut off and restart with thermostat and call me back. He called back and said system never started back up placing it on cool at 65 degrees. Tried just blower fan operation - nothing. Think tripped the transformer? What do you think?

I think you need some specific instruction as to how to handle this that cannot be provided in an open forum.

Get your post count up, get Pro membership, and post in Pro Technical for stuff like this.

I diag stuff like this in less than 30 mins, one man, so I'm a little concerned that this is still an issue.