An HVAC pressure switch is installed in both heating and cooling systems and is a protective device. Under certain conditions which may hurt the system, the switch will open and cause the system to stop operating. Pressure switches are commonly tripped by occurrences like clogged vents or hoses, dirty filters or condenser coils. You may also want to test the pressure switch itself if you are troubleshooting your system. Here PartsAPS will share tips with different issues one id how to test HVAC pressure switch and the second one is how to troubleshoot the Pressure switch if there is any problem. Before we start testing pressure switch let us know the little bit about what pressure switch is.
What is Pressure switch?
To monitor a process pressure and provide an output, a device is designed known as a pressure switch. To detect the presence of fluid pressure, a pressure switch is used. A diaphragm is used as a sensing element for maximum pressure switches. To indicate an alarm or initiate a control action, the movement of this sensing element is used to actuate one or more switch contacts.
What is the function of HVAC Pressure Switch?
To provide a path for an electrical circuit that is triggered at a certain pressure is the function of a Pressure Switch. The pressure switches are used in different places like:
- Air compressor control
- Oil pressure warning light in an automobile
- Industrial process signaling
- A pump controller (turn well pump on and off)
Step by step testing of the HVAC pressure Switch:
Step 1
Inspect the terminals on the pressure switch. Then you should replace the switch if any of them are burnt or badly discolored.
Step 2
To display AC volts, set the voltmeter or multi-meter.
Step 3
To either one of the terminals on the pressure switch, touch one of the probes from the meter. To any nearby bare-metal surface on the system, ground the other probe from the meter by touching it.
Step 4
Check the voltage reading on the meter. The pressure switch should be open if you are getting a reading of fewer than 24 volts. You may have a faulty pressure switch if all hoses, vents, and coils are free of clogs and clean.
HVAC: Pressure Switch Troubleshooting/Replacement Parts
- Turn your furnace on; set your meter to volts AC, so it is calling for heat. The draft inducer should start.
- There should be either two or three wires going into your pressure switch.
- While touching the other lead of your meter to ground, probe one lead of the pressure with one lead of your meter.
- You should be getting 24 or more volts between both leads to ground if you have a two wire pressure switch.
- Then you have a pressure switch problem if you do not get 24 or more volts with the furnace running.
- The problem could be caused by a gas furnace pressure switch by the following:
- Maybe a bird’s nest, wasp nest or debris, stopped your vent
- Maybe your draft inducer is plugged up. Many times the tube is plugged up with water. To hopefully clear the stopped up furnace condensate drain line, you can disconnect the pressure switch tube and run a wet vac.
- The draft inducer hole could be plugged up. Drill to open the hole back up, use a small drill bit.
- Causing water back up and blockage in the pressure switch tube, on high-efficiency condensing furnaces the water drain line could be stopped up. Use a wet vacuum to open the drain back up and take the drain hose lose from the condensing furnace.
- Note it and be careful when troubleshooting the pressure switch. The diaphragm inside the pressure switch can be damaged, if you suck on the HVAC pressure switch to test. It would be best to use a manometer or test with a voltmeter.
PartsAPS hope this will help you troubleshoot your gas furnace pressure switch. If you would like us to let us recommend a pressure switch or part for your furnace, then please share us your furnace’s model number.
