How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Phil Your Own Question
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8511
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
23932409
Type Your HVAC Question Here...
Phil is online now
A new question is answered every 9 seconds

I have a Trane xr80 that is not kicking on the heat. Blower

This answer was rated:

I have a Trane xr80 that is not kicking on the heat. Blower comes on fine. The light on the circuit board does not ever come on. The ignitor does not glow and tests with some resistance on the ohm meter. Gas valve does not appear to open.

Hello, set the fan switch on the thermostat and tell me if the fan comes on or not.... if not, check for a blown 3 amp fuse on the printed circuit card, its an automotive type.

To go much further you will need a multi meter so we can check fo 24volts ac at the furnace transformer or 19volts from the red wire that runs to the thermostat to the bare metal threads on the gas piping.

Customer: replied 7 months ago.
fan comes on
Customer: replied 7 months ago.
fuse is good
Customer: replied 7 months ago.
What will the voltages tell me?

Hello, since the fan runs, that proves the transformer and fuse are good we do not need the multi meter as badly.... we can still use voltage reads on other issues that remain to be seen as we go along however.

Next send me a close up photo of the wiring diagram glued to the inside of the blower access panel on the furnace, photo must be well lit, and *exceedingly well focused...I will mark it up with trouble shooting instructions.

So far it looks like a tripped high limit or door switch if we are lucky, or a bad printed circuit card if we are not as lucky.

Customer: replied 7 months ago.
The unit will go on/off when the door switch is engaged/disengaged...The high limit switches (2) appear to untripped but I'm not 100% clear on what that would look like. They look the same.I will try to get a photo of the diagram but it will take me a while before I can do that. I'll need a couple of hours to get them to you at this point...

Thanks, ***** ***** unplug the furnace, and disconnect the wires from any limit switch or flame roll out switch you want to test then use your ohm meter to see if its open or if the contacts are closed as they should be.

Customer: replied 7 months ago.
Circuit board...

Yes the circuit board.

You cannot tell if a switch is tripped by looking at it... you must disconnect it and use a multi meter set on ohms to determine if it is tripped or not.

The training required to sort these things out is 2 years of community college HVAC labs then a few years in the field working under a journeyman... I can coach people with a base of skills with a multi meter, but if that is not the case we can waste a lot of each others time.

At this point if you can tell me what direction you are from the center of the nearest city I will look for a well rated outfit that can arrive and do the diagnosis and repair for you.

Customer: replied 7 months ago.
Sorry about that vaugue reply... it was the board. I swapped it. Works great. You were helpful.

Good work!

If you would like to rate my work I will appreciate it! Thanks!

Just locate the 5 stars and award me all 5 if you like

Phil and other HVAC Specialists are ready to help you

Related HVAC Questions