My weather maker 8000 furnace 58zav is flashing a 31 led code and won't turn on in heat mode on thermostsat. I turned the setting to automatic on thermostat and it came on and ran for a while but hasn't came back on help please.

Take out the flame sensor clean it with sand paper and put it back.see if it works I had the same ptoblem my problem was solved but on other fourms I heard that code 31 is for pressure switch.I have no idea about pressure swith.u can Google it just write weathermaker 8000, it will take you to havc forum.
Good luck

Check the front/blower panel for list of codes & instructions. Code 31 is pressure switch-related. Try nudging the wires on the switch. If operation is restored, the pressure switch is failing.

Thanks for the info.I will try those things.im still baffled though because it came on again in auto mode on thermostat and every thing ran fine.it just won't call for heat until its really cold could this be a thermostat?

It could be the thermostat, or the furnace locking out due to a malfunction. Keep an eye on the status light when you suspect trouble.

Just to let people know I had a repiar man come out and diagnose the problem for sureand it was a faulty control board. So error code 31 could also be a malfunctioning control board. I'm trying to find a new control board but no success anybody knows where to get one please let me know

Let me Google that for you: Carrier Circuit Board Kit 325878-751 [325878751] - $248.00 : Shortys HVAC Supplies, Short on Price, Long on Quality! - Indianapolis, IN

Carrier tends to constantly make improvements and the part numbers keep changing, this newer control boards may require different wiring harnesses to work.

Happens all the time.

Those guys are always a RIPOFF see below link

Carrier Conversion Board Kit 325878-751 NIB - eBay (item 260523596046 end time Dec-19-09 06:54:00 PST)

Here is a bunch of them.

325878-751, great deals on Home Garden, Business Industrial on eBay!

And I was going to check eBay too. Thanks for being my shadow.

Yep but you also have to watch the Ebay sellers also.

Yep. Read between the lines. They may leave parts out, but their descriptions are accurate. You just have to read them carefully.

The worst is when they say new and you get it and you can see where the 1/4 inch male spades have lines on them from the female connectors meaning that wires were attached already and the board was probably used. Now the sealed bag stuff is OK.