Pressure switch replacement

Check flame sensor , check hoses to pressure switch not split etc

You may need to replace the sail switch. It senses the fan speed and when it connects the gas valve should open and furnace should fire up.

The best thing to do for these units is replace the ignition module, on Ebay they are cheap usually. Clean all orifices where any pressure switches or tubing connects on the induced drafts assembly, Does the pilot ever light?

TRI-COLOR (DSI LED) DIAGNOSTIC TABLE
No. of Red BLINKS
1 Flame sensed when no flame should be present
Verify the gas valve is operating and shutting down properly. Flame in burner assemble should extinguish promptly at the end of the cycle. Check orifices and gas pressure.

2 BLINKS Pressure switch stuck closed/ inducer error
Pressure switch stuck closed. Check switch function, verify inducer is turning off.

3 BLINKS 1st-stage pressure switch stuck open/inducer error
Check pressure switch function and tubing. Verify inducer is turning on the pulling sufficient vacuum to engage switch.

4 BLINKS Open limit switch Verify continuity through rollout switch circuit.

5 BLINKS Open rollout/open fuse detect Verify continuity through rollout switch circuit, check fuse.

6 BLINKS 1st-stage pressure switch cycle lockout If the first stage pressure switch cycles 5 times (open, closed) during one call for heat from the thermostat the control will lockout.Check pressure switch for fluttering, inconsistent closure or poor vacuum pressure.
7 BLINKS External lockout (retries exceeded) Failure to sense flame is often caused by carbon deposits on the
flame sensor, a disconnected or shorted flame sensor lead or a
poorly grounded furnace. Carbon deposits can be cleaned with
emery cloth. Verify sensor is not contacting the burner and is locatedin a good position to sense flame. Check sensor lead for shortingand verify furnace is grounded properly.

8 BLINKS External lockout (ignition recycles
exceeded where flame is established and then lost)Check items for exceeded retries listed above and verify valve is not dropping out allowing flame to be established and then lost.

9 BLINKS Grounding or Reversed polarity Verify the control and furnace are properly grounded. Check and reverse polarity (primary) if incorrect.

10 BLINKS Module gas valve contacts energized
with no call for heat Verify valve is not receiving voltage from a short. If a valve wiring is correct and condition persists, replace module.
11 BLINKS Limit switch open - possible blower
failure overheating limit Possible blower failure, restricted air flow through appliance or duct work. Verify continuity through limit switch circuit and correct overheating cause.

12 BLINKS Module Ignitor contact failure Fault code indicates the module ignitor contacts are not functioning
properly. Replace module.Solid Module - internal fault condition Module contacts for gas valve not operating or processor fault.
Reset control. if condition persists replace module.
3 double 2nd-stage Pressure Switch Stuck Open/Inducer Error
Check pressure switch function and tubing. Verify inducer.

Hi.
If it is stuck open you will need to replace the switch....

Here is a tip that will help you try to figure out why your furnace is not working.

Basic Furnace or Heating System Troubleshooting

heatman101

The pressure switch requires a negative pressure (vacuum) to close the contacts. It is measuring the pressure in the inducer and indirectly ensure there is good combustion airflow throught the heat exchanger. Check for a small vacuum, in the neighborhood of 1" water column. Usually the vacuum required to close the switch is stamped on the vacuum switch. Check the vent pipe for obstructions and correct size and installation.
If the pressure aka vacuum switch does not close the furnace will not continue with ignition, for safety reasons.

This more often than not, indicates that your pressure switch is gone and needs to be replaced. Watch the YouTube video for a fuller explanation and heed the warning to use OEM parts! Gas Furnace Pressure Switch Failure and Replacement Amazon com gas furnace parts

Don't know your furnace model specifics but if it has a powered exhaust blower it must be blowing and the pressure/vacuum switch must be functioning.

Also if you had a malfunction and the high temp or out of burner flame detectors tripped you will need to replace them or manually reset them depending on type to get things back up and running.

Also most furnaces have a safety switch on the blower cabinet door and will not let anything start up if it is not made..had it happen to me loose panel on furnace shut it all down.

listen for the gas valve to click on,,,if you do not hear it clicking on u could have bad gas valve,,,if it is smart valve which was around about 4 years ago they had major troubles and most where dead on startup. if it is clicking on than you might have something in the pilot tube or moisture in the valve,,try banging on the valve some ,,sometimes that will break it up and let it flow past if do right after it clicks in..might have to pull the pilot tube and blow out,,,sorry just dont have enough info at moment for lock down diagnoses,,good luck

try cleaning the burners and or adjust the distance the igniter is from the actual burner .