Blower continiously running...switched out fan control brd, still runs...rmoved all t stat wiring and still comes on
Hi, sounds as though your at the end of your rope!! Yes, this can be a ***** to figure out. So, you replaced the main control/blower board, and removed all stat wires at the stat. I don't know if this is a split gas heat and cooling unit or a heat-pump or the age of the unit? On the blower board, did you remove the stat wires on it first before you took it out and the fan kept running? Or did you switch it out by doing one wire at a time and then putting the stat wires on the new board. What I am trying to find out if you remove the green wire now at the board, have you tried this to see if the fan stops? I'm just trying to rule out any stat wires touching at either end or in the wall causing the fan to run, but I don't believe this to be the problem. Depending on the unit if it has a gas furnace or heat-pump, you need to go to the fan limit control. If it is a gas furnace, you have a fan control that has stuck contacts causing the fan to default and run. If it is gas and a older unit, it will be a Honeywell type with a chrome box on it. Behind the cover is a switch, fan control switch that brings the fan on and off. It rotates and they will get dirty and stick. It will need to be removed a cleaned with a old tooth brush works well. If you have a heat -pump, no gas indoor unit, look for your fan time delay relay. Look on your schematics and it will show you where its at on the unit. It is most likely the cause, burned or contacts welded together. It will say TDR on the schematic. It will send 24 volts to another relay where one leg (hot wire ) that your fan connects to all the time causing fan to run. If I were there on site, with a few checks with my meter would have you on your way, but I'm not. Also. there is a small round fan limit which depends again on the type, that is located on some up by the blower motor with a wire in and out and has a fan reset button on it. By resetting it, it opens the circuit shutting down the fan. Check these things out and keep me posted. If you will, please tell me more on the type of system it is you have. This will make it much easier to trouble-shoot. Please let me know and please be kind when rating me. I thank you for this. I hope I have been of some help to you. I will be here for more help to you.
A/C & Heating Contractor
Jul 01, 2010 |