Here is a documentary on how I replaced a HVAC condensing overflow shutoff device. It's very common for a stoppedup drain to trigger this device and results in shutting off your AC/furnace. I am not a professional. This is for reference only.

Here is an explanation on how it works:    • Explain how does a HVAC condensate ov...  

If you want to buy this online, click on this link http://goo.gl/sFNaj