Inducer motor blowing the wrong way - Intertherm Heating & Cooling

Look to see if the pressure switch contacts open close

3 flashes indicate an issue with either the inducer, pressure switch, plugged condensate drain or a venting restriction.

Clear all debris from the exhaust and intake air piping. Make sure they are not drooping anywhere.
Check the pressure switch and the rubber hoses for blockage.
Blow out the drain line that evacuates the condensation.
On the inducer motor housing, un- plug the rubber hose going to the pressure switch and check to see if there is suction when the motor is running.
Make sure your air filter is clean.
Listen to the inducer motor as it turns for gurgling or any other abnormal sounds.

To make the heater run while you have the cabinet open, tape down the door safety switch. Remove the tape after diagnosos.

The booster motor? Do you mean the inducer motor that helps push the exhaust? If the inducer motor won't shut off when the thermostat is satisfied and everything else does shut off, it sounds like the contacts on the relay that powers the inducer are at fault

what brand furnace is it? is there any blinking light on the control board? is the tube going to the pressure switch blocked? there should be a tube going from the pressureswitch to the inducer motor housing take it loose from the inducer and check for obstruction there,dont blow back into the switch.

I know that it's easy to spend someone elses money but in my experience when you get one actig that erratic it's usually the control board. I would check all the wiring including thermostat. You never know you might get lucky. I hope this helps you. Thanks

Check to see if theres power getting to the inducer motor, also check for loose or damaged wiring. If theres power the motor is bad. If not check the air flow switch, usually a disk shape with a silicone hose attached and two wires... take the hose from the furnace and blow into it and test to see if theres continuity, this switch is normally open and when you blow the switch closes. This is to make sure that the main blower is running so the combustion chamber doesnt burn up (and your house). Make sure your air filter is clean! If the switch is operational it could be the relay that controls the inducer motor, on newer models the relay is on the control board, check for error codes... try these things and if that doesnt work call your local furnace repairman!

PRSSURE, DRAFT SAFGUARD, AUX-LIMIT SWITCH(WHEN USED)OR BLOCKED VENT
SWITCH(WHEN USED) DID NOT CLOSE OR REOPENED (DOWNFLOWONLY)
If open longer than five minutes, inducer shuts off for 15 minutes
before retry.
Check for:
* proper vent sizing
* defective inducer motor
* restricted vent
* excessive wind
* low inducer voltage(115VAC)
* defective blower motor or capacitor
* defective pressure switch
* inadequate combusstion air supply
* disconnected or obstructed pressure tubing
If it opens after trial for ignition period, blower will come on for
90 sec. recycle delay.
Check your air filter for blockage, check pressure switch for a buildup of moisture. Make sure your inducer motor is turning and creating a vacuum to the pressure switch. Make sure all venting is clear and free of water or debris. Make sure there is no water in inducer motor and all drains are draining.

that means pressure switch failure,
with that particular failure you may want to check
you inducer blower, and your ducting between
usually when you get this failure , its more than likely your inducer is not creating enough flow to trigger the pressure sw.
rather than an actual failure of thepressure switch
read you amps at the inducer it should read around .6 running

code 31 indicates pressure switch did not close or reopened during the heat cycle....1st thing to check is the inducer motor,,this is a small motor that turns a small blower wheel that draws the exhaust gases through the furnace and blows them into the vent pipe....1st locate the inducer assembly,,most easily identified by the small plastic fan blade that cools the inducer motor as it runs..1st turn off tstat and turn off furnace power switch..then turn on furnace switch,then set tstat to heat,set the temp above room temp by 5 degrees...remove the furnace front cover,locate the inducer motor,,if it isnt turning,but is warm or hot after a minute or so,likely the inducer motor is bad..if it isnt turning and isnt warm after 1 minute,then likely the main control board is bad,,not turning the inducer motor when it should,,,,,if the inducer motor is running,,then the pressure switch isnt closing,, could be a bad pressure switch but more likely there is a problem with the venting...some possible problems that would cause the pressure switch not to close in an 80% eff furnace [metal vent pipe] are: [1] a blockage in the vent pipe,base of chimney,dead bird at the furnace where vent connects to furnace or down inside the inducer assy,accessed by removing vent pipe from furnace....if all clear the chimney could be blocked up inside,,is the draft good when vent is removed from base of chimney?..if furnace is a 90%+ type [pvc plastic vent pipe],,then check the intake pipe at the furnace by removing it where it attaches to top of furnace..is the intake clogged with anything?..then check the intake and exhaust pipes outside for blockages,,including ice/frost/snow at the exhaust pipe outlet..