Hi, I have a limit switch on an american standard furnace that I think needs to be replaced. How much does it cost to replace one? --173.89.xx.xx

Off the top of my head, Limit switches for that furnace runs from $24 to $36 -- approximately. --47.156.xx.xx

Vacuum, mechanical or thermal? --76.188.xxx.xx

If it helps american standard is a relabeled trane machine, with some troubleshooting experience you may be able to use a trane part to get your unit going again, many times the flash code can guide you to the problem area. a vacuum switch is common to flue pressure - birds or bricks can block the chimney, mechanical is the rotary fan - high temp limit - a blocked filter or vents makes the temp go too high stopping the burner while the fan blows away the heat, a thermal switch is used near the burners to cancel the gas because the bonnet overheated or in the plunum acting as a high limit turning off the gas leaving the blower on to take away the heat. Find the problem and fix it, be safe --76.188.xxx.xx

Thank you for your responses. It is an older mechanical unit that has a dial with temps on it for the limit switch. --65.127.xx.xx

Me thinks the shoes will fix this, I have talked many landladys thru this over the years. --76.188.xxx.xx

As Vee said, those older ones, if it is the one I have pictured in my head, are almost bomb-proof, but they do get stuck over the years. Are you handy or have a 'quality' handy-man capable of first trying the "hit it" as Vee suggests, or, using an air compressor or those cans of compressed air for cleaning out electronic equipment, take the cover of the switch housing, and air/spraying the heck out of the switch and the contacts there. With the furnace power OFF, you might even get a spray can of auto brake cleaner or Electronic Zero Residue cleaner, and spray the mechanical parts of the switch, then again dry/blow it with the air compressor to make sure no residue exists. If that doesn't work, again, if a capable hand-person, most times that whole switch (it's about the size of a single light-switch box) is removable from the furnace. If I recall correctly, it has some probe-like on the back, the part that sticks INTO the furnace fire-box, to read the temp, so work carefully. If you remove it, blow it clean, maybe a VERY small spritz of some lube just on the shaft that rotates the dial, NOT on the temp probe. It'll likely work another 10 years. Can you post a pic of the switch in question? --38.121.xxx.xx

Thanks to all. I have talked to the Furnace contractor owner and the limit switch is OK. False alarm. --65.127.xx.xx