Comfortmaker C9MPD100J14C Only goes on when I unplug and Replug pressure switch wire?

kevin211mvd

Comfortmaker C9MPD100J14C Single stage propain Furnace Brand New Only goes on when I unplug and Replugin pressure switch wire(quickly)? The unit does not show any diagnostic codes on the light, it just shows a heart beat(which means its operating fine). The unit works fine when i unplug the pressure switch wire and just plug it back in.It also heats up the house to the desired Temp i set on the thermostat and then goes off like it should. But it does not go back on when the temp goes lower then what I set it to. I have to do it manually like this everyday and its getting annoying. Does anyone have a solution?

sgthvac

I would say your pressure switch is sticking closed making the circuit think the furnace is already running. Before you replace it though, clean the ports where the tubing connect to the furnace. Clean it with a nail or paperclip. Debris will build up in there and create problems.

kevin211mvd

Ill give that a shot.. But Why would they be clogged if its a brand new unit?

sgthvac

I miised the part about being new, but that being said you would be amazed at some of the junk that comes out of a new furnace. Did you install the furnace yourself? If not call the contractor back to fix the problem.

kevin211mvd

Yess I installed it myself ... I think i found the prolem though now im getting a diagnostic code. 2 blinks Pressure switch closed when should be open

SD515

With the unit off, unplug the wires and the hose to the switch and check the continuity…should be open. If it’s closed, the switch is stuck closed and should be replaced.

__________________
Kyle

Just because you can, doesn't always mean you should

kevin211mvd

but now im getting 3 blinks pressure switch open when should be closed..... Has anyone had this same problem its frustrating...

kennzz05

switch should be open when not running and closed when running pull the wires and see if theres continuity thru the switch when off(shouldnt be) and than again with draft fan running (should be) or if you want to read voltage...24v when off and no reading when running