What does a pressure switch look like ?

Obvious that the unit isn't getting gas to the ignitor.
To receive gas to the ignitor, there is a gas valve located upstream of the burners.
Have a friend turn on the heat while you are up close to the furnace.
Once the ignitor gets hot, there will be an audible "click" at the gas valve when the low voltage controls call for the gas valve to open to supply gas to the burners.
Listen for it.
If you hear a click, and the furnace still isn't firing, you need to check to see if someone has closed the gas shut off supply valves located on the gas line.
If all the shut off valves are open, you need to verify you have gas pressure in front of the gas regulator.
If you verify have pressure on the upstream side of the regulator, you will need to verify there is also pressure downstream of the regulator.
If there is gas pressure upstream but none downstream, replace the regulator.
If you have pressure downstream of the regulator, and the gas valve clicks, but furnace doesn't light, replace the gas valve.
LP has higher pressure than natural gas, and is dangerous.
LP is heavier than air and will sink to the floor or lowest area.
One static electricity spark is all it takes and an explosion can occur.

The fuel tank pressure switch is on top of the fuel pump and the fuel pump is inside the top of the gas tank.

You probably need to replace the pressure switch. There are several options like the pressure range, port location, port size and if it has a pressure relief valve. The link shows an example.
New Heavy Duty Air Compressor Pressure Switch Control Valve 90 PSI 120 PSI

Hi it is probably the igniter pack under the controls depending on the model it could be a fairly large single pack with a pressure switch wired from each knob or individual switches. You will need to remove the panel and see where it is then test each one, don't touch it they really bite, if you need more help let me know. Ray

Usually any control knob will activate all four igniters it's usually a faulty pressure switch rather than the igniter pack module.

Miele use pressure switches to activate the igniter pack if none of them work the fault is the igniter pack itself.

check the current to the clutch pack. The ac control and the blower motor will both have to on . If ok check for low gas pressure in the system (low pressure switch will switch off) or high head pressure ( blocked system or excessive gas level) will also switch off the unit.. Have it check at an ac shop

I would say you have a problem with your pressure switch, you may need to adjust it down. The pressure switch is normally located under plastic cover where your on off switch is on the compressor. There should be a screw with arrows next to it. Try that, otherwise you may need a new switch

if the Ac compressor clutch isnt engaging even with a hot wire then the solonoid has packed up if does engage then it could be a pressure safety switch although i would empty the system with my machine and weight the gas i take out as if less than 150 grms then it will not work ,never mind the pressure its the weight of gas in the system that makes the switch allow the compressor come on

P1782 - P/ES Circuit Out Of Self Test Range.
Means that 2-4 pressure switch sense circuit failure. It basically means that the transmission solenoid pack needs to be replaced.

The pressure 2/4-OD Pressure Switch is part of the pressure switch of the transmission. The pressure switch are located in the solenoid assembly. The switch provide input information to the Transmission Control Module (TCM). The switch will inform to the TCM is pressure exist in a specified hydraulic circuit. the TCM uses this information to verified that the solenoids are working or not.

Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)
- Transmission shift shock

Possible Causes:
- Low transmission fluid level
- Dirty transmission fluid
- Faulty 2/4-OD Pressure Switch
- 2/4-OD Pressure switch poor electrical connection
- 2/4-OD Pressure switch circuit is open or shorted


Hope helps.