Greetings. I just took the advice provided by a guy with the handle "labman" that was sent to someone several years back--2005. He was having problems with his furnace's limit switch as am I. My blower works fine, just putting out cold air. I replaced the igniter thinking this was the problem as there was no flame, but it did not resolve the issue. So, I place a piece of wire between the two contacts on the limit switch and voilà, I have flame and heat coming from my furnace.

This is my question, actually two: (1) Is it safe to leave the furnace running with the wire connecting the two contacts on the limit switch? And, (2) Where can I order a new limit switch?

Thanks much for any assistance. Best wishes. Steven.

No,its not safe to run furnace with wire jumper

You might find the correct limit switch on eBay, get the numbers off old limit
You could try a local hvac parts house, or try some local hvac contractors

Good luck

Hi wmproop. Thank you for the information. I am wondering if you could assist a bit further. I called the supply shop in my town, and they do not have the Supply Air Limit Switch I need in stock. Further, with the holidays, I am told the part would not be here until Tuesday (January 3) if they order it. Sooooooo, I do not want to keep running electric heaters in part of the house in the meantime. I will check eBay. However, what is the risk I run if I continue to use the wire jumper on the supply switch for a few days? If you know, I would appreciate this information. Thanks much.

Simply put, leaving the limit jumpered runs a risk of burning down the house. Keep using the electric backup heaters until you can get the correct replacement limit. Its just not worth the risk. Most likely something caused the limit to fail. Once you get the new limit, watch the furnace closely to see if the new one trips. Most common causes of high limit failure are dirty filters, clogged secondary heat exchanger, or clogged evap coil if you have central a/c, or weak blower motor or dirty blower wheel..