Checking the pressure switch on a gas furnace Video

Measuring ohms on an energized 80% gas furnace

Does it matter ...
Does it matter which wire goes where on a pressure switch? I unhooked mine and I'm not? sure which order they need to go in.

Respond to this ...
Respond to this video... TWO thumbs up on the use of meter. ? system did not let me take the thumb down away .

@kisssfan TWO ...
@kisssfan TWO thumbs up. great explanations of use of the? the meter

Just fixed my ...
Just fixed my parents' furnace by clearing the pressure port in the combustion chamber blower housing. (By poking a wire into the port until the very hard obstruction cleared.) Does this mean that the chamber, or the blower housing, is caked with hardened soot? Should I disassemble the blower housing to clean? it?

there is? no power ...
there is? no power throu that switch, since he removed the circuit board leads at the beginning, so he is able to ohm it, the inducer motor created a negative draft which will close a properlly operating pressure switch allowing for an ohm reading. DONT ohm it with those leads connected

Arent you suppose ...
Arent you suppose to never use your ohmeter on a? live circuit ??

The thing? to ...
The thing? to remember is the pressure swith has to start open, then close or the furnace will not heat.

i was under the ...
i was under the impression that you could not test for resitance or ohms while the power was on or you could? fry your meter. Do you have a special multi-meter ?

Nice? meter
Nice? meter

hey man nice vid I ...
hey man nice vid I just Graduate remindes me of school I? remember them days keep up the good work

Part 2 of my ...
Part 2 of my question The reason I sought out your instructional video is that I simply? don't trust this guy! He wants to either replace the motor/switch or the entire unit. It is 15 years old so I understand the age issue...but if I performed this test, and am getting a good reading, and had heat output last winter, and the unit is running and putting out heat now, then what would you make of my situation?!?

Part 1 of question ...
Part 1 of question Hi kisssfan - thanks for the clear video! I have a follow up question. I just performed the? test you detail in your video, and I received "0" with my ohm meter. But I had the unit "tuned-up" for the winter a couple of weeks ago, and the service man indicated that I would need to replace the heat inducer motor and/or pressure switch on this unit. He indicated that if I don't do this, I will certainly not be getting any heat out of the unit this winter.

The problem with ...
The problem with this conventional method is you can't see at what exact pressures they open/close and you cant? test the internal diaphragm. Thus, you can get false positives all day long.

Nice Video, I just ...
Nice Video, I just wanted to share with you a new tool I've invented that accurately tests pressure switches without the furnace even running. It works by simulating the Draft Inducer. With a manometer attached you can find out exactly? when the switch opens and closes, thus proving it's working properly. You can also find out if there is a weak diaphram, and CALIBRATE adjustable pressure switches! I posted it as a video response, I hope you like it!

If I may add....... ...
If I may add.......if you use a Magnehelic across the pressure switch, you will have a MUCH better idea where the problem lies.....whether you have? a bad switch or another problem elsewhere......You can also save a bit of time and simply check voltage with the leads connected, or unplug the NO/NC or both and just leave C connected and check for 24V.....that will tell you right away if your switch is closing....but using a Magnehelic will also tell you if the switch SHOULD be closing.

I just had a bad ...
I just had a bad snow storm that? dumped 17.5 inches of snow in the area and the pipes/chimney were plugged on the roof for the furnace from the snow so i had to wait for the snow to melt and it worked, I was getting the LED status error code 31 because of the plugged pipe for the inducer I believe.

Nice video, thank ...
Nice video, thank you? !

Thank you for all? ...
Thank you for all? your video postings. They certainly help clarify and reinforce HVAC/R studies

why not check kor ...
why not check kor 24 volts across the? switch when the inducer motor starts

On this particular ...
On this particular meter, infinity would read as an "OL" meaning? open line. In other words, the meter is actually sending out a voltage from it's batteries thru this switch and will display that voltage in an "ohm" value if it receives it back. If the circuit fails to close there will be no voltage back to the meter, and it can be thought of as reading infinity because the signal response will never come back to the meter. The signal sent out just continues on and on forever.

a really high? ...
a really high? number

Do you mean by ...
Do you mean by infinity reading a large number or essentially a number close to? zero? Thanks doc

The pressure switch ...
The pressure switch shown in this? video does not have an impeller in it. There is a pressure sensitive diaphragm and contacts that allow 24 volts to pass thru it when the inducer fan is operating. The inducer creates a negative pressure which is transfered to the pressure switch via a tube which in turn closes the diaphragm and contacts. This then allows the sequence of operation to continue. It is a safety switch which proves the proper operation of the inducer fan.

No we haven't ...
No we haven't shorted out a transformer, nor have we blown the 3 amp fuse located in the circuit board. The wire terminals are factory insulated for that reason. If you turn the power off, the inducer fan as well would be turned off and it could not pull the negative? pressure required to close the pressure switch. So, ultimately that would be useless. Thanks for your concern.

have you ever? ...
have you ever? shorted out the transformer when you dropped the wires to the casing like that?!! you could just turn the power off to the unit first.

An impeller is in ...
An impeller is in those switches??

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