My renter tried to change the stat, now the fan is running all the time.
The Manual says check Fuse line, but I can not locate it !
http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/ii394g-25-1.pdf

I have changed the switch limit so far, and removed the thermostat, still the fan is running.

Need to knowwhere is the fuse line/

If the furnace has a circuit board, there is often a fuse on it. These fuses are of the automotive blade style & usually either 3 or 5 amp.

EDIT: In the troubleshooting section of the manual to which you linked it states one cause of the fan staying on is a blown fusible link. They must be replaced with an identical part. Find the 120 to 24 volt transformer & follow the output from the 24 volt side. The fusible link shouldn't be far from the transformer output.

I changed the fuse link
And then replaced the old borad with a brand new one the board
, the new borad has a fuse (3 amp )on it.
As soon as I truned it on, the new 3 amp sparked and burned.
I assume if I change the 3 amp it should not last eathier...

What should I do next?

I changed the fuse link
and then replaced the old borad with a brand new one the board
, the new borad has a fuse (3 amp )on it.
as soon as I truned it on, the new 3 amp sparked and burned.
I assume if I chnage the 3 amp it should not last eathier...

what should I do next?

You have a short somewhere. Disconnect the thermostat wires at the furnace, replace the fuse & try again. If the fuse doesn't blow, the problem is in the stat or wiring.

You have a short somewhere. Disconnect the thermostat wires at the furnace, replace the fuse & try again. If the fuse doesn't blow, the problem is in the stat or wiring.


When the fuse blew the last time, I had the stat wiring discounnected. Only two balck wires were connected.

So I am sure the stat is not shorted.

When the fuse blew the last time, I had the stat wiring discounnected. Only two balck wires were connected.

So I am sure the stat is not shorted.

Were the wires disconnected at the stat or at the furnace? If only at the stat, the wires could be shorted due to a mouse chewing on the insulation, etc.
Where do these two black wires come from & go to?

Were the wires disconnected at the stat or at the furnace? If only at the stat, the wires could be shorted due to a mouse chewing on the insulation, etc.
Where do these two black wires come from & go to?

Discounnected in the furnace, so the wirring to the stat was nothing do with blown fuse.

The two black wire are connected to C and Y

I asummed they are the power to the unit.
If not, then are they coming from,A/C ?

The two black wire are connected to C and Y.
If not, then are they comming from,A/C ?

They do go to the A/C outdoor unit. I'd disconnect them too, just to eliminate any possibilities external to the furnace.

They do go to the A/C outdoor unit. I'd disconnect them too, just to eliminate any possibilities external to the furnace.

Thanks for you help
I will try that this aftroon and post results tonight.

Frist-I got the two wire (A/Cs) diconnected and had only the t. stat wires connected.
And put new 3 AMP fuse.
The fan stopped running. I thought it was fixed.
So I wend to T. stat and put the fan "ON"
But to my surprise, the fan did not run.
I took the fuse out and the fan started running ( so when the board in it not running)-
Then I put fuse back and A/C wires connected. The fuse did not blow but the fan was not running eaither.
Out side temp was around 70F so I put the stat to 80F to see if the furnace ignited.
Nothing! No ignition for 4 minutes, I gave up for the night.
I am now confused.

If you have a digital t-stat, depending upon make, you could have up to a 5 minute delay after powering up. You very well be frustrated by that delay. When they say 5 minutes, they mean at least 5 minutes but never less.

The fan runs with the fuse out just as if the fuse were blown. I guess it's supposed to be some sort of safety thing??

Here is current status, since It is getting cold around here I appreciate any help I can get:I checked the tranformer In 120 out 27.7 V
I put new fuse, No fan, so I shorted G (Fan) to R and got the fan running
Then I shorted W (heat) to R and got he sparks.
So I removed the new T. stat and put theold one back. Put the fan on "ON" fan started. Put the stat on Auto the fan stopped that is good.
I believe the Fan is fixed with the change of control board, limit switch & Fuse link
But the put the t. stat on heat 90F the furance started to sparked for several minutes but did not ignite. After several minutes I put the heat on "OFF" so not damge something else.

Now I might have new problem which is
" the heat does not strat ( gas is not ignite depite sparks)Did I damge something else? What should I do next.to get the heat

Here is current status, since It is getting cold around here I appreciate any help I can get:I checked the tranformer In 120 out 27.7 V
I put new fuse, No fan, so I shorted G (Fan) to R and got the fan running
Then I shorted W (heat) to R and got he sparks.
so I removed the new T. stat and put theold one back. put the fan on "ON" fan started. Put the stat on Auto the fan stoped that is good.
I believe the Fan is fixed with the change of control board, limit switch & Fuse link
But the put the t. stat on heat 90F the furance started to sparked for several minutes but did not ignite. after several minutes I put the heat on "OFF" so not damge somthing else.

Now I might have new problem which is :
" the heat does not strat ( gas is not ignite depite sparks)Did I damge something else? what should I do next.to get the heat

Thanks

It would seem you are not getting gas for one reason or another. First & simplest things to check are: (1) Make sure any manual gas shut off valves are open. (If propane ensure there is gas in the tank & the tank valve is on.)
(2) Check the gas valve on the furnace to verify it is set to "on".

Is there a small (1/4") aluminum tube attached to the gas valve? The presents or absence of said tube will tell me if the furnace uses a pilot (lit by the spark) or not.

The valve is set to "ON"
It is natural gas not propane
The manual (link above) says do not try to lit the pilot manually & I can hear the sparks when heat is called for but no ignition ( at least for several minute that I was watching it)

The valve is set to "ON"
It is natural gas not propane
The manual (link above) says do not try to lit the pilot manually & I can hear the sparks when heat is called for but no ignition ( at least for several minute that I was watching it)

Presuming the gas is turned on to the house, you have either a clogged pilot orifice or the furnace's gas valve is not allowing gas through.
Most gas valves have three terminals which are marked PV (pilot valve), MV (main valve) & a third marked Com, Comm, Common, or MV/PV. During the ignition sequence, measure the voltage between PV & Common. You should get +/- 24 volts AC. If you do, & hear a slight click the valve is getting power but is not opening or the pilot is clogged. Pilots can be easy or a bear to get out.