problem with concord 80 gas furnace

djmanley

changed out honeywell gas valve and furnace worked great. Had a small gas leak and tightened up coupling. restarted furnace after rechecking for any additional gas leaks and it would not cycle through and was flashing 3 lights signalling pressure switch or auxillary limit stuck open. Looked at schematics and traced the violet wires down to the orange tubing checked tubing clear no water in it and could easily blow through it. Put tubing back on and again same signal. Any suggestions or helpful hints would be greatly appreciated! Thank You

Patrick Eubanks

Check the opening going into the pressure switch. Take a piece of t-stat wirn and stick in the opening where the tube connects to the pressure switch. Sometimes these will clog.

djmanley

will try that next and see what happens. If that doesn't work any other suggestions.

JJboy

Also check limit switch. Using multimeter in ohms you should have 0 ohms across the terminals

__________________

**Always kill the power ** Hot air rises, but heat will always move from higher to lower temperatures. ** Real man shoot in manual. ** If it ain't grounded, it ain't dead.

thestig3

Was the gas valve an OEM replacement or an universal type? I've had a call back on another techs GV change out, he used a universal and didn't check his outlet gas pressure on GV. GV putting out too much heat and tripping high limit. Adjusted pressure and I was good to go. No problems since.

djmanley

I know this is going to sound dumb but looking at the schematics I can't figure out which is the limit switch. Could you describe where it is located and what it looks like? This would be of great help! Thanks

Doc Holliday

Doc Holliday

In the first pic there is only one high limit switch, usually there are more than one tied in series.

djmanley

I greatly appreciate all the wonderful suggestions that was offered by all. The one from Patrick Eubanks is the one that did the trick I had tried this previously but not with that small of a wire and with his idea was able to get in there far enough to push what ever was in the opening on past and it is working perfectly now! Just in the nick of time as cold weather is moving in tonight! Thanks again