# 1 year old Goodman GMH81155CN Gas Furnace problem



## bcarter (Oct 18, 2010)

I have a
Goodman GMH81155CN Gas Furnace

115,000 BTU Furnace, 80% Efficiency, 2-Stage Burner, 2,000 CFM Multi-Speed Blower, Upflow/Horizontal Flow Application

as of last night these have been the symptoms:

1 click
2 click
3 click - RED LED at the bottom motor circuit board comes on
4 click - RED LED is still on
5 click - sounds like a double click and exhaust motor comes on the RED LED is still on, but after 2 - 3 seconds the exhaust motor cuts off, RED LED turns off, and the cycle repeats after about 2-3 seconds.

The HSI doesn't glow at all.

I switched off the heating functionality at the thermostat control, then went back to the unit to pull these fault codes:

3 - pressure switch stuck open
4 - open high limit

I used this site to check the high limit switch
IHateMyFurnace.Com we'll help you get along with your furnace.

according to this if i get continuity its functioning. I got continuity. 


Any Help would be great!
Thank you


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## kok328 (Oct 18, 2010)

So then that leaves the problem of the pressure switch being stuck open.
Test the pressure switch manually and see if this is the cause of the problem.


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## paul52446m (Oct 18, 2010)

bcarter said:


> I have a
> Goodman GMH81155CN Gas Furnace
> 
> 115,000 BTU Furnace, 80% Efficiency, 2-Stage Burner, 2,000 CFM Multi-Speed Blower, Upflow/Horizontal Flow Application
> ...


  When you take a continuity test you have to take the wires off the control you are testing because you could get a false reading.
  The same think holds true with the pressure switch, take the wires off if you want to check with continuity. You can take the hose off the other end
 and leave it on the pressure switch, the pressure switch should not have continuity, then blow on the hose and see is you get continuity. Make sure you do not have a plugged stack. Make sure you do not have any water in the hose going to the pressure switch. Make sure you do not have any 
 cracks in the hose going to the pressure switch, it only takes a small crack to stop the pressure switch.  
  I don,t understand the clicking as you are saying. Check the sequence of operation in your book. The first click should be the inducer fan, then the pressure switch makes,  then after 15 to 30 seconds the glow bar starts
 to heat, and after that  the main gas comes on. 
 Now the inducer fan can't start unless the limit and all roll out switches are made. let me know how you make out. later Paul


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