A/C Heater Question

This is a wierd issue, but I will do my best to explain it. Any advise is greatly appreciated.
I have a newer Trane A/C installed last summer. The A/C works great. If the fan is on auto and I set the thermostat at 75, when the temp reaches 76 it turns on, when it gets down to 75 the fan and a/c turns off, just like its supposed to.
The issue is with the heater. If I turn the fan to auto, it never comes on, but if I turn the fan to "on", the heater works great. The issue is, I have to leave the fan to on, which means it will run until I manually turn the fan off, even if the heater kicks off. For example, if it is 74 in the house and I turn the thermostat to 75 and switch the fan to on, the heater kicks on and pours out heat until it hits 75, but the fan keeps blowing after the heater turns off. If the temp drops a degree the air the fan is blowing becomes hot again.
Everything seems to do its part, but the auto fan on the heater side, even though it works fine on the a/c side. I figured it was a faulty thermostat, but I've tried four different ones and they all do the same thing.
More info on the unit, it has 4 wires to the thermostat, White, Yellow, Red, and Brown (Ground). There just isn't much to it. The heater is electrical.
Does this make since, any ideas?
snipped-for-privacy@wideright.net -aj
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Hello AJ,
Normally, the thermostat turns on the fan in cooling mode, but, the heat sensor turns on the fan in heat mode, so, since it's four wire stat, it's a gas heat unit.
Now, depending on the model Trane, the heat can turn on the fan either by sensor or time delay relay, usually mounted to the circuit board, which is probably what you have.
So, since it is still under both labor and manuf. warranty, I'd go for that, and have them fix it.
Take care, Paul
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Thanks for the reply. The unit is definately electric and I got the unit off the back of a truck and somehow got it in and working on my own. I paid someone to sweat the pipes and drain/refill the freon and other then that it was fairly easy. It was in the middle of summer when I did it and I was just happy the A/C worked, I tested the heat then, but only by turning the fan on. I think this issue is probably over my head though and will most likely call someone out.
Someone replied that a similiar issue stating that the thermostat doesnt have enough juice to turn the heater on automatically and I need to install a relay. That make any sense to you?
-aj
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You either have the wrong type of thermostat or a defective furnace. There should be a temperature sensor that turns the fan on in heat. Some models use a differemt type of thermostst though. This is why there contractors. The manufacturers have schools that are set up to teach contractors how to install their equipment. You need to get one of those to figure it out. You can keep guessing, probably with the same results. Get someone who knows waht he/she is doing, safer and cheaper in the long run. BTW, the brown is probably going to the green (G) terminal. That is what makes the fan work in COOL.
Good luck.
Stretch
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This is Turtle.
First it can be atleast 8 different things wrong by what you say but most likely as i can see is your short one wire to operate the fan only of the furnace. this may include adding a fan relay to do this operation.
Now you have 4 wires white, yellow, red , and Brown.
White-- operates the heat. yellow-- operates the cooling. red-- Operates the 24 volt power to the thermostat. Brown-- Has a common to operate the thermostat. Green-- is missing which operates the fan.
So you need 5 wires in this case to have the fan operate independently of the system. You need another wire from the thermostat to the furnace to get the fan to work.
Now that i read more here Stretch is correct in needing the heat sequancer changed out also with the wiring job of the green wire.
TURTLE
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You bought stolen goods? You deserve all the trouble you have and more.
Next time someone mugs you or breaks into your house and steals things, don't complain.

Remove NOPSAM to email me. Please let me know if you have posted also.
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It is not stolen, just from an inside connection. Unfortunately the guy I bought it from knew just enough to help get it in and I'm trying to avoid paying someone to come work on it, if I can do it myself.
Turtle If the green wire was missing, why would the fan still work with the A/C? Or is the green wire just for the heater?
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AJ wrote:

The green wire is the safety ground.
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You should learn the meaning of metaphors before you use them. "Fell off the truck", "off the back of the truck" mean stolen, whether you stole it yourself or you bought it from an employee who stole it.
Now you say it is "from an inside connection". If that connection isn't the guy who rings thing up on the cash register and who rang you up and gave all of the money you paid to the company he works for; and if the connection isn't the owner, who can give away his stock at whatever price he chooses, or at no charge, it still sounds stolen to me.
What inside connection are you talking about?
If you got a lower price than you could have because the guy you bought it from stole it, then you are also one of the thieves.
You still sound like you stole it.

Remove NOPSAM to email me. Please let me know if you have posted also.
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Plus, if the OP ever tries to get warranty parts/work done on it and it has been reported as stolen, watch out! Someone will be coming to his house to take it away....
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