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no heat...help

14K views 42 replies 5 participants last post by  hvaclover 
#1 ·
I have a tempstar furnace which worked fine till a week ago..for a time the blower motor would make a humming sound before kicking in...now nothing. I checked the thermostat and there is no spark when you flip the mercury switch side to side. I tried the crossng w/r trick at the thermostat and on the furnace..nothing...no spark no nothing. What is the next step? new blower motor?

Thank you
Joe Buhler
 
#3 ·
One good test is to pull the motor and see if it spins freely without noise. The if you are comfortable you could plug in the motor to see if it starts okay. White is ground and any other color will work for hot. Most are black, blue and red for different speeds. Of course be real careful so that you don't short out the motor. If you have never done anything like this before then ignore my advice here.

As hvaclover said, check power first.
 
#4 ·
i have power going to the furnace and the motor turns freely with no noise. I pulled it out and it is clean and in good looking shape. I checked the power entering the furnace and it is all good to go. I read some where about touching the w + r i think wires together right at the furnace it's self....nothing. Is it possible the motor is blown and not allowing a full circit back to the switches?
 
#6 ·
LOL..no sry i got sent out to work for a couple weeks just got home.:whistling2:

anyways no the burners are not coming on...it is like it is dead in the water. i checked the power where the wire enters the furnace as it is tied in with merets. Good power there..i chased the blackwire down and it runs to the swtich on the bottom panel (safety Switch i am guessing for when the panel is open) ..good power there. Then it heads under to the blower motor i believe.
 
#14 · (Edited)
there are no fuses anywhere...i removed all panels and plugs and checked inside and out. I am not getting any power in side the unit, i still have 120 going in from the swtich and the wires where it enters the furnace tho. Guess i am going to have to get on the waiting list for a furnace guy around here at 150/hr....damit


sorry forgot to say THANK YOU to you guys for all the help trying to trouble shoot this furnace grief for me...it is really appreciated.


~Joe
 
#18 ·
Okay here is where the wires run to..from the safety switch they go to a box, the name on the box is "Heatcraft" model # FTC5-EH01 , on the right hand side of the box at the top it has a wire at a plug that says "Limit" , then below that on the right hand side it says "Valve". On the left hand side at the top it says "COM" and below that it says "24 vac". In the center there is 2 wires going to 2 plugs with a label over both saying "Blower" 1 goes to a plug labeled "com" and 1 goes to a plug labed "NO". From there they go up to the top of the furnace to another box it is a "Honeywell" along the right hand side of that box there are 7 wires and from the top it says:

Spark no number
TH-W #7
24V #6
24V GRD #5
Burner GRD #4
PV #3
MV/PV #2
MV #1

does that help you any?
 
#22 · (Edited)
Okay i taced the wires into the furnace..they join up inside the furnace at the top left hand side..there they are just tied to 2 other black/white wires..they go down and into a panel by the lower motor. The white wire splits..one end goes to what looks like a coil of some sort and the other wire goes to a plug that leaves that box and heads to the motor. The black wire also splits when it enter the box...1 goes to the same coil as the white on did and the other goes to the back of a 7 wire plug area.
 
#23 ·
Okay i taced the wires into the furnace..they join up inside the furnace at the top left hand side..there they are just tied to 2 other black/white wires..they go down and into a panel by the lower motor. The white wire splits..one end goes to what looks like a coil of some sort and the other wire goes to a plug that leaves that box and heads to the motor. The black wire also splits when it enter the box...1 goes to the same coil as the white on did and the other goes to the back of a 7 wire plug area.
Are thy joined with wire nutS?
 
#24 · (Edited)
with merets or i guess wire nuts..(yellow)..they both are tied with merets and head down into the furnace. The white goes straight to the lower panel, but the black of course goes to the safety panel switch and then to the lower panel also. I have good power to that point i know for sure(on the black that is)
 
#25 ·
Turn the light switch on the furnace off. Remove the wire nut (they should unscrew).

Once you have the wires from the switch disconnected turn the switch back, check across the black and white wire. Should Be 120 volts.

Make sure of the voltage and tell me what it reads. Before you answer I want you to check the black wire from the switch to ground and tell me what it is .
 
#27 ·
Reconnect the wires.

In the blower section is there a metal box with the the letters W C R Y and R.

What we are looking for here is the theromostat wire connection.

The heat wire goes to W terminal and should be white in color.
There is also a R terminal with a red thermostat wire to it.

There is a C terminal. There should be nothing connected to it unless you have air conditioning.

Locate these and tell me.
 
#28 ·
okay there are a ton of wires and they go as follows;

"C" white wire
"W" white wire
"R" white wire
"Y" has 2 a red and black wire going to it
"G" has a white wire

yes i have central air.

somebody has had them apart as they are all marked with duct tape on each one.
 
#29 ·
Making progress now, good.

OK, these will tell a big part of the problem.

Make sure you reattach the Yellow wire nuts to the wire they came off.

Once you make sure they are on good and tight I want you to turn the light switch on the side of the furnace to "ON".

Push in the safety switch (might have to wedge it closed). Make sure the thermostat is turned all the way up.

With the safety swich pushed in check R to C. you should have 24volts.

Tell me when you do that.
 
#31 ·
Ok now we are going to check the transformer. Thats the big coil that the black wire from the safety swich goes to.

Is that what you see? The black wire going to the big coil?

Tell mw hat you see. I'll be here til we find out the problem for sure.
 
#33 ·
The big coil is a transformer. There should also be a white wire going to the coil. It steps down 120 v to 24 v.

The 24 wires should come out of the opposit side of the transformer rom whee the black and white wire 120v went in. They will be of smaller guage and usually not white and black. Find were thes connect and see if there is 24 v present.
 
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