The unit is a Westinghouse gas heater that works, but the fan does not come on when I have the settings to quot;heatquot; and quot;autoquot;. If I set the fan to quot;onquot;, the fan kicks in and my place gets warm. On the other hand if I set the AC to quot;coolquot; and quot;autoquot;, it works perfectly...the fan comes on when it needs to. I thought it might be the thermostat, and I bought a new one and the same problem happened.This began only after I changed a round 15amp fuse near the electrical outlet...if this help anyone who know about these things. I took the motor out and checked all the wires, but they look fine.Aside from replacing it (I know I should), any ideas on what the problem could be?Thank you!
A 37 year old gas furnace is about 35% fuel efficient and getting worse every year. Perhaps its time to consider replacing it with a 90+ High Efficient unit and save some operating cost and gain more comfort. Furnaces should be cleaned and checked yearly, filters changed every 2 months or so. How much is your gas bill? how many cubic feet of gas are you using monthly?
It sonds like the fan switch to me not the thermost. If the unit is functioning no sense to replace
Simple one for me. The fan comes on in cool because the tstsat energizes a relay that brings it on in the cooling mode. That realy is not used in the heat mode. The gas furnace relys on a temperature swith to close when the flame has heated the exchanger to a set temp. That temperature switch is bad. It is a 3 x 5: silver box near the top left of the unit as you face the control side. WARNING!! This is a dangerous situation because you are now relying on a safety control to shut down the burners when the box gets too hot with out a fan running. Get that fan in the on position and leave it there until you get this fixed. Pull that fan control/limit out and replace asap.
DSM Rooster are right, There is a bi-metal thermostat located above the heat exchanger that turns the fan on durning the heating cycle. It has a twisted metal coil that extends anywhere from 6-18 into the furnace. After 37 years of use the coil has probably fatigued and broke. New ones are readily avaliable at any HVAC supply house (menard's,and lowe's etc may even have them) they're only about $40 and easy enough to replace. Just pay close attention to where the wires are attached before removing them, write 'em all down maybe even draw yourself a picture. Don't laugh you'd be surprised how many times you take something apart thinking you can remember where everything goes and then get distracted by kids,dogs,wife etc, and end up forgetting. ***Be careful of a jumper on the new one too. There may be a metal bar that acts as a jumper between the fan side and the limit side. On some furnaces that jumper is cut so low voltage can be used on one side of the switch. If it's cut on your old one then cut it on the new one.*** Also make note of your set points on the dial and set the new one exactly the same. Use your thumb to hold the dial face still while adjusting the set points, try not to twist the dial too much as you set it, It is possible to break your new switch by twisting it too hard.. Good luck.......
I would consider myself lucky to get 25 years from a gas heater. You are so far over the max that you should replace it. There is a thermostatic switch on the fan. It measures the heat in the heat exchanger. It turns the fan on only when that heat reaches a preset point. That way you will not blow cold air out in the winter. Changing the wall thermostat's fan switch to on bypasses that thermostatic switch inside the furnace. Since bypassing it turns on the fan, it is a safe bet that the thermostatic switch inside the furnace is the problem. The fan is supposed to come on, and stay on, when the wall thermostat is set to cool (A/C) and the A/C is switched on because it is above the preset wall thermostat point. In other words, there is no delay like there is in the winter; when the compressor runs, the fan runs.
