Furnace High Limit Switch Open

Locate the white limit switch.

Furnace high limit switch open.

I have a 1994 lennox 80 mgf series furnace and there is a 4 ligh flashing which say high limit or rollout switch open. The switch makes sure the furnace is operating safely and at its desired settings. The limit switch will open periodically to prevent over heating. It reads the temperature of the plenum and waits until it gets appropriately warm.

Some furnaces provide extra safety features by wiring two or three high limit switches in a series that check the temperature in the furnace at different points. They will be mounted near where the flame may rollout the front of the furnace due to venting blockages heat. Depending on your furnace model the switch will be surrounded by a silver or white cover. It will be located at the top of the panel.

Founded in 1982 goodman manufacturing is an american company that produces heating and air conditioning equipment for residential and commercial customers. It s also known as a fan limit switch or simply a limit switch. I have the the amana air command 80 high eff gas furnace and the unit works for 3 4 hrs cycling on and off normally then will shut down and won t start again until the unit is powered off reset. So to put it simply the limit switch tells the furnace fan when to turn on and when to shut off and it tells the furnace to shut down if it is overheating.

Attempting to reset the furnace limit switch while the power is connected may result in electrical shock. Goodman residential furnaces contain multiple limit switches to ensure safe operation. The vent limit switch which is also referred to as a fan limit switch and is typically shaped like a small metal disc prevents damage to your furnace by shutting the furnace down in the event. The high temperature limit switch is an important device used in forced air furnaces powered by gas or heating oil.

Rollout switches and high temperature fuses are different from limit switches in that when they open they will not close again unless reset as in the case of the rollout switch or replaced as in the case of the high temperature fuse. Remove the cover by lifting it upwards or pulling it off to reveal the body of the switch and two metal arms. Some of these parts are shown on the left.