Need help !!! furnace wiring

[LI Pets]

I'm on the road I have no heat. I had the furnace bench tested before I reinstalled it, now having trouble getting it going. Here's what I have: frpm the wall going to the furnace 2 blue black wires, I assume t-stat apink 12 volt hot and a white ground.

From the furnace;
2 black 1 yellow 1 white

I put a multi tester from a ground to each of the 4 wires from the furnace. The yellow, white and 1 black indicate ground. I took the remaining black wire and connected to the 12 volt pink hot and I heard clicking. I took the white from the furnace and went to the white ground to the wall. I tried crossing the remaining yellow & black from the furnace crossed them as if they were going to the t-stat. Tried a few different variations. Can't get the fan to go on. Nothing happens.

As a safety precaution I turned the propane off, so I at least expected the fan to go on.
Can any one help get this wiring squared away or tell me what to check. I,m boondocking tonight.

[azflycaster]

On my 75 TW the wires are as follows
Blue (2) - Thermostat
Yellow - Ground
Red - +12 volts

1976 used the same colors as well.

Only one wire should be at ground. One should be at 12 volts.
If you ohm between the wires from the thermostat they should be open (infinity) or closed (0 Ohms) depending on the setting of the thermostat.

Hope this helps...

[LI Pets]

Thanks, I try that shortly.

[lewster]

Bob,

Furnaces have the +12VDC and the -12VDC (ground) to them all the time. the control (on/off function) is performed by the thermostat wires (usually blue). You might have a t/stat problem.

Be sure that your power and ground are connected. Connect the 2-t/stat blue wires to each other at the back of the t/stat and after a few seconds, your furnace blower should come on. After purging the chamber, initiating the sail switch (completing the circuit for ignition) and heating up your time delay relay (assuming that you don't have direct spark ignition or an igniter board), the gas valve should open, the electrode should spark and you should get furnace ignition.

Try this and let us know what happens!

[LI Pets]

Well I tried that yellow wire still no change.

I took off the exhaust tube and spun the blower motor it was free.

Lew not sure what you mean by T-stat problem, I'm not using it, I crossed the two wires going into the furnace?

[lewster]

Originally Posted by LI Pets

Well I tried that yellow wire still no change.

I took off the exhaust tube and spun the blower motor it was free.

Lew not sure what you mean by T-stat problem, I'm not using it, I crossed the two wires going into the furnace?

Bob,

See if you can find the power leads that go directly to the blower motor and isolate them. Apply 12VDC to these wires in the proper polarity and the fan should start. If not....bad motor.

See if you can find the model # of your furnace and let me look up a circuit diagram for it. Another problem might be the time delay relay (TDR). If that is bad, your blower won't work either. (I'm assuming that you have an older model furnace and not a new one with an igniter board and direct spark ignition).

[LI Pets]

I was just about to pull the unit out to work on it.

I was looking thru the side openings with a new Led flash lite, when I saw a bare wire.

It was the yellow wire coming out of the unit, I think when it was tested the guy pulled the wire out so hard he stripped it on the sharp steel casing.

Anyway I I got some shrink wrap on it then the + and - changed.

Just for anyone else to know.

THe two blacks are T-stats.

The yellow is ground, the white to the pink 12+

We're warm and toasty in Topsail.

[azflycaster]

Glad to hear that everything worked out well.

Happiness is a warm Twinkie!