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, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
Type Your HVAC Question Here...
Phil is online now
A new question is answered every 9 seconds

I have a Trane natural gas forced air furnace model number

Customer Question

I have a Trane natural gas forced air furnace model number BLD45L936A furnace that was built in 1983. It has a problem with consistently igniting the burners. If I reset the furnace by turning off the power and turning the control valve to the off position
for 5 minutes and then turning everything back on, the furnace will ignite and everything will work as normal. The problem is that it will not consistently work. I have to reset the furnace to get it to work. Is there a way I can isolate the bad part or parts?
Submitted: 1 year ago.
Category: HVAC
Expert:  gotoman for ac replied 1 year ago.

This unit should have a sensor for flame. Sensor located next to last burner. Looks like a large piece of wire with one wire attached. Clean with sandpaper and retry furnace. Russ

Customer: replied 1 year ago.
My furnace has electronic ignition
Does your suggestion work for that?
Expert:  gotoman for ac replied 1 year ago.

Yes . It should light and prove flame thru sensor. Russ

Customer: replied 1 year ago.
I cleaned the sensor with sandpaper as you suggested and the furnace will not ignite. No sparking from the electronic ignition. What is the next step to isolate the cause of the problem?Thanks,
Expert:  gotoman for ac replied 1 year ago.

Can not find any info on that furnace. Searched Trane archives and it comes up obsolete. I will opt for another expert.

Expert:  Phil replied 1 year ago.



Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip-icon at the right end of the toolbar at the top of this dialog box,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip-icon, look for the '+attach files' link at left of your send button.

I can mark it up with trouble shooting instructions. You will need a multi meter ($30 at a hardware store) and some experience working with appliances, let me know a lot about your skill sets in those regards.

If none of this in your skill sets, tell me which direction you are from the center of the nearest city and I will look for a few well rated service outfits in your area.

We can go from there.

Customer: replied 1 year ago.
Hello Phil, I do have a multimeter and have repaired electric and gas appliances in the past. I have attached some pictures. Let me know if you need anymore. You can call my cell at(###) ###-####if that works better for you.Thanks,
Expert:  Phil replied 1 year ago.


See if you can find a 'sequence of operations' note on the diagram or elsewhere on the furnace and send me a photo of it.

I also need the brand and model number of the gas valve.


Customer: replied 1 year ago.
I looked all over the furnace and could not find a sequence to operation note. I could find a model number on the gas valve but the lighting instructions sheet pasted on the outside of the furnace says that it is a 36E Series gas valve. According to the Operating Parts Replacement List that came with the furnace documentation, the catalog number for the gas valve is WG19X215. I am also sending pictures of the gas valve.
Customer: replied 1 year ago.
Phil, I also found the attached in my owner's information manual.
Expert:  Phil replied 1 year ago.

Hello again, that furnace has some pressure switches that I am not familiar with, and lacking a sequence of operation on that furnace I am not confident that I can help you... I will opt out, so other of our experts here can see your question.

Customer: replied 1 year ago.
Phil, Thanks for trying. Hopefully, someone can help.