Coleman furnace model # 7956A856 ,

The problem I'm experiencing is that the burners will not ignite. It was working fine this morning came home from work to a cold house. The pilot is still lit,. has current, the thermostat is functioning, as is the limit switch as there is continuity from the one terminal to the other the only thing I can think of is the small transformer died,. no burner and no fan turn on to provide heat.

Any sugestions??
Thanks for any support anyone can give,.

Check for voltage out of the transformer. It should be around 28 volts AC.

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Originally Posted by Grady White

Check for voltage out of the transformer. It should be around 28 volts AC.

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Thanks Grady,. I did check that originally and I'm not getting anything,. the meter shows .001v. AC at 2 terminals, And nothing on the others on the transformer,. that's what made me think it was the problem. 120 v. AC at the power switch in and out and 120 v. AC at 1 orange and 1 brown connection on a pair of thermal sensors (?) mounted on the face of the cabinet right next to each other. (they actually share the center mounting screw)

Check anything else ? Or just surmise it's going to be the transformer,.
Thanks again,.

From what you are saying, it sounds like you are not getting any power to the transformer. Check the wiring diagram on the furnace to determine which wires are power to & from the transformer. You should have 120 VAC in & +/- 24 VAC out.

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Originally Posted by Grady White

From what you are saying, it sounds like you are not getting any power to the transformer. Check the wiring diagram on the furnace to determine which wires are power to & from the transformer. You should have 120 VAC in & +/- 24 VAC out.

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Thanks again,. I was trying to determine what fed the current to the transformer The schematic that's glued to the transformer cover is deteriorated and only 1/3 of it it still there. I'll have to backtrack the feed wire to see where it takes me in the morning I've been up since 4 AM to go to work this morning and I'm dead tired at this point. I tried searching online for a workable schematic but just got a maze of various search engines leading me from one to the next without any luck in finding the diagram,.

A very BIG thank you for your assistance with this so far,.

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Originally Posted by warlock49766

Thanks again,.. I was trying to determine what fed the current to the transformer The schematic that's glued to the transformer cover is deteriorated and only 1/3 of it it still there. I'll have to backtrack the feed wire to see where it takes me in the morning I've been up since 4 AM to go to work this morning and I'm dead tired at this point. I tried searching online for a workable schematic but just got a maze of various search engines leading me from one to the next without any luck in finding the diagram,..

A very BIG thank you for your assistance with this so far,..

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Just wanted to let you know the findings,. someone else may visit this site with the same issues.

It was a faulty "roll-out switch" giving me all my headaches,. thanks for all your help and suggestions,. Terry

Glad you got it figured out.
BTW, those two thermal sensors which share a center screw are probably the fan & limit switches. The fan is a normally open & closes on temperature rise to bring on the fan. The limit is a normally closed & opens on temperature rise to shut down the burner if the furnace gets too hot.

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Originally Posted by Grady White

Glad you got it figured out.
BTW, those two thermal sensors which share a center screw are probably the fan & limit switches. The fan is a normally open & closes on temperature rise to bring on the fan. The limit is a normally closed & opens on temperature rise to shut down the burner if the furnace gets too hot.

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Gotcha' Grady,. thanks again for your input and help. Nice to have the furnace up and running again with the temps outside in the high teens and low to mid 20's