Furnace Problems? Part 2

MCSE · 11-30-2006, 09:44 PM

This is a follow up to "Furnace Problems?" a couple threads down. I thought I better repost as a new topic because we thought the issue was resolved.

I redid all the wiring from the thermostat to furnace and now the burners will not ignite. I disconnected the thermostat wires directly from the furnace and placed it in manual and it still will not light. The blower operates fine during the cycle but there is no ignition. The pilot light is fine. Last night the manual mode worked so I used that to keep the house warm.

There is a component on the part which contains the pilot light knob(to turn on the pilot light) that says "Genral Controls". This is where the thermostat wires hook up. There are also two other blue wires on this component which seem to go to what looks like a solenoid by the incoming power connections. Can I put the two blue wires together and bypass that component if I wanted manual mode? It appears to have no connection to the limit control. I just need to get some heat going and I don't mind spending another night getting up every few hours to put the furnace in manual.

Any suggestions would be greatly appreciated by my children, pregnant wife and myself....lol...My sob story.

#CARRIERMAN · 11-30-2006, 10:01 PM

Hi MCSE

Go to your thermostat, take the R and W wires off of the thermostat. Touch the two of them together, it should have a small spark but the burners should come on. Let me know what happens.

Rusty

MCSE · 11-30-2006, 10:04 PM

Hello Rusty,

It does spark but the burners do not ignite.

#CARRIERMAN · 11-30-2006, 10:06 PM

Hi MCSE

Stupid question, is the knob on the gas vale in the on position?.

Rusty

MCSE · 11-30-2006, 10:08 PM

Yes, the knob is on and the pilot light is lit.

#CARRIERMAN · 11-30-2006, 10:17 PM

Hi MCSE

Than I will say I have to feel for you tonight. You need to replace the gas valve. I would reccomend a Robertshaw gas valve if they are available in your area. I believe the one you would need is a 720-402 if your burner manifold is 1/2" or if it is 3/4" you will need a 720-502. Either way, I wish I had better news for you. I now myself have about 1 1/2' of snow in my town. Let me know if I can help you any further, one question before I go. When they sold you the fan limit switch did they tell you to break out the tab in the bottom center of the new switch. If they didn't or you fogot to, you just ran 120 volt through a 24 volt gas valve and thermostat. If this happened you may end up replacing the thermostat also.

Good luck
Rusty

MCSE · 11-30-2006, 10:18 PM

Could I have done something wrong when rewiring the thermostat? My thermostat is only using two wires and when I replaced them I did one at a time. Therefore, they must be correct. Is it possible that the little black box(on top of the part that has the pilot light knob) got shorted out somehow??? The power was off when I rewired so I cannot see howit would have got damaged???

As well, is it possible to bypass that black box(mentioned above). It does not appear to be connected to the limit control.

MCSE · 11-30-2006, 10:21 PM

They said that the tab did not need to be broken off because the furnace only had three wires going to the limit control. I looked at the old limit control and it was not broken off either.

MCSE · 11-30-2006, 10:23 PM

I hear ya....about the snow that is...

I am in Edmonton Alberta and we have loads of snow too. Plus, it has been reaching temperatures of -40C as of late(with wind chill).

#CARRIERMAN · 11-30-2006, 10:25 PM

Hi MCSE

That makes me feel alot better about there being no damage. But it doesn't do much good to keep you warm. I cannot believe that there was one of those old General valves still in operation, I thought the last one went down with the Mayflower. I think ITT shut down the General controls division almost thirty years ago.

Good luck
Rusty