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Jerry M.
Jerry M., HVAC Technician
Category: HVAC
Satisfied Customers: 153
Experience:  29 Years of experience in HVAC design -install- service -controls /Comm. & Residential
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my lennox ghc-5500n gas fireplace will not ignite. The pilot

Customer Question

my lennox ghc-5500n gas fireplace will not ignite. The pilot light burns fine, but when I flip the switch from the wall, nothing happens. IT also has a wall switch for the blower, which works fine.

any help would be greatly appreciated
Submitted: 7 years ago.
Category: HVAC
Expert:  Jerry M. replied 7 years ago.
I will be happy try and help. Right inside of the fireplace opening, at the top edge and to the left, or possibly on the left side-wall towards the top, there should be a manual-reset temperature safety switch. This switch shuts the unit off in the event the flue is restricted. There is a red button to push to reset the switch - this button may or may not be readily visible - if not, you will need to remove the screws holding it in place, pull the switch out enough to access and reset the red button, then re-install. If your fireplace works after doing this, then check your flue pipe for restrictions! Let me know if this works - if not we'll keep going! Thanks! XXXXX
Customer: replied 7 years ago.
Thanks for the quick reply Jerry. My name is XXXXX XXXXX I live in Morgantown, WV.

I looked and there does appear to be some type of sensor with 2 wires in the upper left corner. The part is secured by 2 small screws with a standard 1/4 inch hex bolt head. It is round, approximately 1/2 inch in diameter, 1/2 inch deep and has a part number on it = "G158-42 L400 97/2". I do not see a manual switch of any sort.

What is the next step?
Expert:  Jerry M. replied 7 years ago.
Try removing the 1/4 inch hex screws and see if you can get a glimpse of the backside of the switch, and whether or not there is a reset button.I will be online, so I can respond back. Jerry
Customer: replied 7 years ago.
To view the part number, I had removed the screws, it does not look like a switch, but it could be a sensor. it is just a small, white 1/2 inch round, 1/2 inch deep cylinder with two red wires connected to the back.
Expert:  Jerry M. replied 7 years ago.
Here is a way to test this switch, but only if you are comfortable trying it. Take a short piece of wire, bared at each end, and "jumper it across the two terminals on the switch, then have someone turn on the wall switch to the fireplace. It won't take long to tell if the problem is with the switch - if the fireplace lights, then we know the switch is bad. If it still doesn't light, we'll go from there - keep me posted Jerry
Customer: replied 7 years ago.
I tried to jumper the switch, no luck. The switch is really odd... there is no button to push. I wouldn't have even called it a switch. I have a voltmeter... but not sure where or how to test.

Expert:  Jerry M. replied 7 years ago.

I have sent along a web address that will allow you to download a document that has wiring diagrams,etc. Go to - when you get to that page, simply click on "fireplaces" at the top of the left-hand menu. After you get to the "fireplaces" page, click on the "owner resources" category on the top menu bar, then click on technical manuals from the drop down menu. Find your particular model and download the .pdf - This should be quite helpful & you said you already have a voltmeter, so hopefully you can work your way through the wiring schematic and locate the problem.... please let me know if I can be of further assistance in ANY way! Best wishes - keep me posted! JERRY M.

Edited by Jerry M. on 4/27/2010 at 4:52 AM EST
Jerry M. and 2 other HVAC Specialists are ready to help you
Customer: replied 7 years ago.
Thanks Jerry. I am going to give this a try and then I will let you know how it goes. Thanks.
Customer: replied 7 years ago.

thanks again for your help. Turns out the problem was a pretty big deal. We had a local guy come look at it and it took him 3 trips and ordering 2 parts to get it fixed. You helped me at least know I needed someone to come help.

Thanks again,