Heater won't ignite, pressure switch

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  #1  
Old 03-30-03, 02:31 PM
joelgris
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Heater won't ignite, pressure switch

I have a Trane central unit that will not ignite. It is about 7 years old and uses natural gas. The ignition board has a fault LED that is giving a code for a "pressure switch problem". The manual says the igniter will not work if it does not detect an open condition at the switch. I've found the switch on the unit by tracing the wiring. Can I just replace the switch and fix the problem? I'm concerned about doing that. I don't know if negative or positive pressure must be on the sensing line before the switch will operate correctly. Do I need to investigate any further before ordering the switch? The unit did the same thing about two weeks ago. I messed with the switch and tried to pull off the line to make sure it was not obstructed but all of a sudden the unit started working normally.

It is a cold weekend and this unit heats my children's bedrooms!
 
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  #2  
Old 03-30-03, 03:39 PM
fjrachel
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Tap the switch to see if it will open...you may have a drop or two off water in the pressure tube causing the switch to stay closed. Remove tube and check for moisture.
 
  #3  
Old 03-30-03, 03:48 PM
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fjrachel is right

either it is sticking closed, hanging open, has moisture in the switch or tube, or tubing may be cracked. also check the interior of the inducer motor assy where the tube hooks up. i have seen buildup on this port restricting flow through the tube to the switch
 
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Old 03-30-03, 04:00 PM
joelgris
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I just went out and tapped on the switch and it started working properly. I guess I should just replace it?
 
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Old 03-30-03, 04:24 PM
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try this

blow out the tube to the fan assy, disconnect the tube be sure it is clear. reinstall tube with no trap. replace switch if it happens again
 
  #6  
Old 03-30-03, 04:29 PM
joelgris
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Thanks to both of you for the answers. I'll do what you suggest. I appreciate the help.
 
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