Carrier Series 160 heat is not turning on.

Old 11-20-08, 04:18 PM
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Carrier Series 160 heat is not turning on.

The A/C works and the blower works. When I set the TS I get a signal to the air handler.

When I manually move the PS plunger and deactivate the switch the ignitor turns on, lights the gas and the blower turns on.

The PS in the schematic shows it should be N/O but the PS plunger is always pressed against the switch. Is this correct?

I removed the PS and made sure that the tube was not clogged.

I also bypassed the thermal switch which is in series with the PS and it made no difference.

The control board LED is flashing 31 which is Pressure, Draft Safeguard, Auxiliary-Limit (when used), or blocked vent shutoff (when used)

When I manually deactivate the PS the LED is on continuously.

Thanks for the help.
Old 11-21-08, 04:47 PM
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The switch is open, and the plunger is pushing it open when the furnace is not running. But a soon as the inducer comes on, the plunger is sucked away from the switch, closing the contacts, and the furnace runs.

You have confirmed that you have manually made the switch part work, by some method. Therefore, we know the contacts/switch part of the PS is good. But what we DON"T know is if the furnace draws well enough, or if the PS diaghram has a tiny leak.

Did you try to take off the vacuum tube from where it plugs into the inducer, and ream out that hole in the inducer?

If that does not help, disconnect the vacuum tube from the inducer side, leaving the tube still attached at the PS. Now suck on the tube a little and see if the plunger pulls in, and while doing that, pinch off the tube real tight with flat pliers, and see if the plunger holds, after you stop sucking, and while you are still pinching it off good. You must squeeze off that tube very well, or else this test can fool you.

If the plunger backs off, repeat the test making sure you are pinching it good with flat pliers. If the plunger backs off toward the switch, then replace the PS.

If it does not, you need to find out why the furnace is not pulling. You probably should blow out your condensate drain tube each way, as this can cause the draw through the furnace to reduce and cause PS to not work. Blow both directions - toward th drain and back into the furnace. If that does nto help your furnace run, check the vents that let exhaust air out and perhaps fresh air in, for obstruction.

Get back with us with any of you discoveries, please.

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