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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Intertherm natural gas furnace model no. m1mbo77abw will not

Customer Question

Intertherm natural gas furnace model no. m1mbo77abw will not turn on
Submitted: 11 months ago.
Category: HVAC
Expert:  airheatman replied 11 months ago.

Will fan or anything come on?

Customer: replied 11 months ago.
no nothing moved thermostat to high used electrical sniffer to see if voltage was present
Customer: replied 11 months ago.
set thermostat for fan to run and nothing their as well
Expert:  airheatman replied 11 months ago.

Do you have a volt meter for troubleshooting?

Customer: replied 11 months ago.
but not at house where furnace is located
Customer: replied 11 months ago.
Interthem does not have an air filter and everything covered with dust.
Expert:  airheatman replied 11 months ago.

Ok our first step in troubleshooting is to verifiy we have 24 volts between C and W on board when calling for heat.Can you get the meter?

Customer: replied 11 months ago.
Assume I need to check the voltage on furnace circuit board?
Customer: replied 11 months ago.
Any idea why blower fan does not turn on when set on thermostat?
Expert:  airheatman replied 11 months ago.

Very possible that either we are not getting 24v out of transformer or tstat could be bad, Try jumping the R and G wires on control board and see if fan will come on and R and W to see if heat will come on.That will tell us if thermostat is an issue.

Customer: replied 11 months ago.
OK how does this work if I have to sign off and come back latter to further troubleshoot?
Expert:  airheatman replied 11 months ago.

Just sign in to JustAnswer and go to "MY Qusetions"

Customer: replied 11 months ago.
Thanks will sign off and do some trouble shooting.
Expert:  airheatman replied 11 months ago.

We will go from here when ready

Customer: replied 11 months ago.
Will look for your reply later, the Interthem furnace has poor set up for air filter do you know of anything to improve air filter or add on as inside is covered with lint. Trying to think how I could filter return air before it goes into heat exchanger. Furnace is in a small space, manufactured home
Expert:  airheatman replied 11 months ago.

Is return pulled through the louered panel or from top of unit?

Customer: replied 11 months ago.
Not sure believe the top?
Expert:  airheatman replied 11 months ago.

Can you attach a photo?

If you have a paper clip icon on your page you can attach using that link.Or

You can upload the pictures using the tiny pic site .

Here is a link to the site.

Click on Browse , select the file from your folder.then click UPLOAD NOW.

They will give you a quote to enter in the box to verify you are a human.Enter the quote and click UPLOAD NOW

You will see your picture on right side of screen.

Then copy the link URL for email & IM

Paste that link here on the site.