I have replaced two evaporator fans for family members who could not afford a repairman. One of the units was designed to suck air in the other to blow it out. You can save big bucks by using the knock off motors. I bought one for kid u not $35. The last one was $75 :-( but the original TRANE motor retailed for ever two hundred. I had to cut the shaft to make it fit and figure out that the original dual capacitor could still be utilized to start the compressor even though the knock off motor required its own run capacitor but everything is clearly labeled so it doesn't take a rocket scientist to figure it out. The knock off motors have reversing wires such that when you switch them the direction of the fan motor reverses. Sometimes I switch them just for the heck of it. It's kind of fun. No difference in cooling or efficiency as far as I can tell. Sometimes I trick my wife and ask her if that fan is sucking or blowing. After she answers I go out and switch the wires to prove her wrong. :-). This sounds hard but it's really easy. Unless you want to leave this earth literally and figuratively make sure the 220 breaker is OFF. Some electricians put the 220 in the main breaker box but only label the low voltage control circuits. They figure this way there will be fewer guys messing with their own AC compressors because those guys will be dead. If you haven't switched off a dual circuit breaker with at least 40 amps you've still got 220 volts in the circuit! Regardless of the fakey 20 amp breaker labeled AIRCONDITIONING SYSTEM. when all else fails check the voltage going into the contactor switch with a volt meter. If you don't know how to do that call a repairman and while you write that check for $500 smile while telling yourself IM STILL ALIVE :-)

Ok...did some more digging and I now know why the fan was trying to turn, hat case had become live and so it was acting as a neutral. I have never seen this before, is this common? All three wires have a resistance of 40ohms to the case, so what could cause that problem. Thanks, Neil

"The one tech just added one pound of Freon." Oh now theres an HVAC destined to greatness!!!! LOL More then likely acdude is right on. Probably original relay and its tired. Obviously neither one of them are all that familiar with a simple air conditioning circuit. Intermittent problems could be annoying sometime. Instead of just walking away one of them should have at least put in a new fan relay and said to you "see if this works, I'll be back in a couple days or so" A new relay is only a couple of bucks.

It depends on the age and brand of the furnace, is it gas, electric, heat pump or oil fired? Most of the older furnaces developed in the sixties and the seventies had fan limit controls and mechanical relays that energized the fan circuit. The newer furnaces today utilize a continuous fan feature, to indicate that there is a problem with the furnace. This type of furnace usually will have a round glass window on one of the panels and you can look into it and see a blinking light, that light indicates a certain code-and using a code key inside the panel area one can usually determine a likely cause. Whats the age of your furnace? Model and Serial Number? You can probably type the model number of the furnace into the browser bar and find a location on line that indicates its electrical diagram. Get that and post it here-I'll look at it for you and tell you what I would check. E.W.