[joey_trivia]

I went on vacation for 10 days. Before I left, I turned off my unit from the termostat, letf the unit on OFF and fan on Automatic. Also turned off the pilot on my gas water heater. When I got back, the blower which is part of the furnace was running! who knows for how long. The house was at 90 degrees, (I live in texas) it took about 6 hrs to cool down to 82 which is what I like to have it at. Once the AC stopped, the blower kept running, So I thought maybe my thermostat was out since the buttons have always been pretty lose and it was an old one anyway. So I went and bought a new digital with programming features. I put it on, it works great, however the blower still does not stop. It has been running non stop. The AC seems to stop a and go accordingly to the temp on the termostat. (eventhougt, I think it is taking too long to cool things down).

So my question is, what do you guys think its wrong? Why is the blower still running?

Please help..
Thanks

[labman]

The blower is controlled by a relay switched by the thermostat. Additionally there is a timer that leaves the blower on 90 seconds after the thermostat shuts off the compressor. Chances are the relay is stuck closed, although, it could be the timer. If a good rap on the relay shuts the blower off, replace the relay. Otherwise, you will need to do some checking, seeing if the relay coil has 24 volts, and checking the timer.

[joey_trivia]

It sounds like it may be the relay like you said its "stuck Closed". So can you please be so king to help me test it?
First of all, what exactly do you mean by "a good rap on the relay" and how do I do that? Where is the relay?

Also, how can I check the timer? And where is it?

I am fairly familiar with working with electricity so I will take the necessary precautions.

Thanks a lot!

[labman]

On newer furnaces the relay and timer will be on a circuit board. On older ones, they are little boxes mounted near the other controls. Follow the wires from the blower motor back to them. Take a screwdriver, and with a flip of your wrist, hit the relay with the handle. If that stops the blower, the relay was stuck. Another test is to see if the coil terminals of the relay have either 25 volts AC, or on a board 12 volts DC across them. If not, and the blower is running, again, that means the relay is stuck.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

[bobodaclown]

Just a quick thanks. Had a stuck relay on a Train TWE030C140F1. Fan would run forever. Thought it was the relay. But it would keep running even with the Thermostat disconnected. Thanks for your help.