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Tim H.
Tim H., HVAC Professional
Category: HVAC
Satisfied Customers: 3971
Experience:  Experienced in all aspects of HVAC, both residential and commercial.
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My thermal zone furnace does not turn on at all. No lights

Customer Question

My thermal zone furnace does not turn on at all. No lights on the control panel. Thermostat clicks but nothing at furnace. It's a Thermal Zone, Model # ***** Serial# *****
Submitted: 1 year ago.
Category: HVAC
Expert:  Tim H. replied 1 year ago.

Hi, I'm Tim and I'm an HVAC expert here to help answer your question(s). Please provide all the information I ask for since I'm not onsite. At the end of our dialog you will be asked to rate my service, but please wait until then and all your question(s) have been answered satisfactorily. Thanks for your business!

Have you checked for a blown fuse on the control board?

Customer: replied 1 year ago.
the 3 amp fuse tests good
Expert:  Tim H. replied 1 year ago.

Does the furnace have incoming power as measured with a voltmeter? 120 volts?

Expert:  Tim H. replied 1 year ago.

If not, need you to take a couple measurements and get back to me. Get a voltmeter, set to "volts AC" and measure incoming voltage (120 volts) and also take a measurement across C or COM to R at the board. We should have 24 volts there. If you can upload a clear picture of the wiring diagram, this will help me tremendously.

Customer: replied 1 year ago.
I have voltage
Expert:  Tim H. replied 1 year ago.

Did you see my last post?

Customer: replied 1 year ago.
okay, I have voltage to the on/off switch, I have voltage to the cover door switch and I show voltage going into the control board at the bottom last 2 terminals on the right. the rest of the control board shows no voltage.
Expert:  Tim H. replied 1 year ago.

If no voltage across C or COM to R, then it would be a burned out transformer.

Customer: replied 1 year ago.
there are 2 transformers in the unit, one(small) looks like it's for the thermostat and the other is for the furnace.
Expert:  Tim H. replied 1 year ago.

It would be the thermostat one.

Expert:  Tim H. replied 1 year ago.

You can also take the thermostat off the wall and measure across R to any other terminal. You should have 24 volts.

Customer: replied 1 year ago.
is there a part# ***** that one?
Customer: replied 1 year ago.
I have the following connections at the thermostat.....RC, RH, W, G, Y
Expert:  Tim H. replied 1 year ago.

RC-RH should be tied together. You can measure from either one of those to any other terminal.

Customer: replied 1 year ago.
OK, I get 0 volts at the thermostat
Expert:  Tim H. replied 1 year ago.

OK, that would be a bad transformer, then, if furnace has power. You will probably need to purchase part online as local dealers may not sell to you unless you're a contractor. Found this site that sells Thermal Zone parts. You can probably call, give them your model number, and they can locate that transformer for you.

Expert:  Tim H. replied 1 year ago.

Let me know if you have additional questions. Otherwise, good luck! Thank you for using Just Answer and please don't forget to rate my service as that's how experts get paid (Thanks in advance for any bonus left). Otherwise experts work at their own time and expense. Feel free to post back with any other questions.

Customer: replied 1 year ago.
will do, called the folks at the website, waiting for return call.
Expert:  Tim H. replied 1 year ago.

OK, thanks!

Customer: replied 1 year ago.
just to recap, you don't think the control board is the issues?
Expert:  Tim H. replied 1 year ago.

Nope, not if you have no low voltage. You need to have 24 volts available for the control circuit. You said you have nothing across C or COM to R at the board. You could tip the board over, and examine the back to see if there are any burned or scorched areas.

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