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abcd_hvac · Oct 12, 2011, 02:06 PM

I have replaced the gas valve, Fan Limit switch but heat doesn't come on. Can someone help me?
Don't know anything about the furnace as far as brand name. Standing Pilot and Pilot works. I have 24 volts at transformer.

parttime · Oct 12, 2011, 02:44 PM

Hi and welcome, could you post some pictures? There should be a hi-limit switch that you could check in the mean time. Good luck

mygirlsdad77 · Oct 12, 2011, 04:23 PM

Going to need to trace back the wiring from the gas valve and see where power is being interupted. Pics of the furnace and controls will help.

abcd_hvac · Oct 13, 2011, 05:07 AM

I have checked All the limits that are there and they are fine.

mygirlsdad77 · Oct 13, 2011, 03:34 PM

So you have 24v at the transformer. Do you have 24v at the gas valve? Have you tried jumping your thermostat wires to see if it will kick on? Try that. Please let us know.

abcd_hvac · Oct 14, 2011, 05:17 AM

I think that I may found the problem. I have a wire coming from my gas valve going to my transformer and at this same piont I have a red wire from the t-stat there. I think that the wire from gas valve need to go to common on my transformer. I have downloaded pictures. I guess.

mygirlsdad77 · Oct 14, 2011, 06:02 PM

Well, good luck on this and please do let us know what you find. I would have to put my multi meter to this and trace wires to really see what is happening. Pretty basic setup really, but hard to explain through a keyboard. I see one limit that has no wires going to it at all (the white one right behind the gas valve). I just don't feel comfortable giving too much info on a system that has bypassed limits. Could get very dangerous in a hurry if you know what I mean. You may want to test the relay to the right of the transformer. Sorry I can't be of more service to you on this. It may be a good idea to call in a heating tech. They should be able to straighten this all out in short order. Take care.

abcd_hvac · Oct 15, 2011, 09:24 AM

I got the burners to light but Ihad to put the Fan limit on manual. The blower did not come on. I moved the wire form the gas valve TR that was at R on the transformer to common. I'm cert. HVAC I'm just new at this.
Look at Picture 384. You can see there is a wire from the t-stat and a wire from gas valve TR. I lift the red wire from t-stat on R on the transformer. I took the wire that was hooked up at R with the red wire from T-Stat and put it on Common. So now I have 1 wire on R on transformer and the wire from the TR from gas valve to common.

mygirlsdad77 · Oct 15, 2011, 03:06 PM

Do you have a honeywell fan/limit with a round dial in the middle? If so, spin the dial by hand, and if the gas kicks on, then someone wired the limit wires through the fan control, Usually fan control is on the left and limit is on the right (if installed vertically). The fact that putting the fan on manual on on the fan control kicked the gas valve in tells me it is wired incorrectly. Check it out. Should say fan or limit where the wires are hooked. Af for the gas valve, one side should be to common, the other side should run through all limits and thermostat then to r on transformer. Is there a wiring diagram with the unit(should be on the inside of the blower door). Sounds like someone did a little creative rewiring. Just follow the wiring diagram and set it back up the way it was from the factory. Hope this helps. Let me know.

abcd_hvac · Oct 18, 2011, 04:53 AM

Yes I do have a Honeywell Fan/Limit and checked it last night and it was wired wrong. I turn the system onbut still no blower. I traced the wires coming from the fan side of the fan/limit and found out that one wire was hooked up to the normaly closed contact on the fan controlled center. The other wire wasn't hooked up to anything. I guessing that wire neeeds to be hooked up to a wire going to the blower. Right?

mygirlsdad77 · Oct 18, 2011, 04:18 PM

You have humbled me my friend. Ive got to admit, sometimes it takes me awhile to trace all the wiring on a unit and get it all straightened out after someone else has wired it incorrectly. And that's when Im right there with my hands on the furnace. I just don't have the capability to figure this out with you through a keyboard. Sorry man, I really wish I could help further, but I wouldn't be able to sleep at night if I guessed at this any further. Sounds like you have a decent idea of what is going on, and I wish you the best of luck, but Im afraid I won't be able to be of any further assistance.

Hopefully one of the other pros here can help you out.

abcd_hvac · Oct 19, 2011, 04:48 AM

Thanks for the help. I think I just need to figure out what the blower isn't kicking on. I think it has something to do with that one wire that is coming from the Fan/Limit switch. Thanks Again.

mygirlsdad77 · Oct 19, 2011, 03:04 PM

If everything else is working at this point, you are going in the right direction. The neutral to the fan just needs to hook to the nuertal on the power coming in the furnace or a nuertal post with the other neutrals. Then the other wire to the blower needs to go through your fan controls. Once you get this all fixed up, make sure the limit works. You can test this by turning that wheel all the way clockwise when the burners are lit, and it should make the gas valve kick off while keeping the blower running. Just want to make sure your limit/s are working.