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Topic: Pressure Sensor for R134 gas. Air Conditioner. (Read 2133 times) previous topic - next topic


Hello, I would like to see the feasibility of diagnosing some Air conditioner units with Arduino. I would like to add some pressure transducer to the high and low line and read the values from an arduino.

Could someone help me find a pressure sensor for this purpose?
It would be really convenient that it comes from eBay as shipping is very high in other websites.

Any general information is greatly appreciated

Thank you very much


You have to be careful with possible leakage, i'd stick with some nice emmerson PT4 transmitters
(4-20mA) and connect them as described (the second one) on this page:

I work with refigurants all the time and in my opinion: the few bucks aren't worth the risk of leakage
or blown up avr's.

Best of luck!


Thank you very much for your suggestion and recommendation kenny.

As per your experience with HVAC systems, do I need to by special R-134 or refrigerant specific pressure transducer?
or any pressure transducer within the desired range would work?

I am planning of carrying some beta testing and based on results decide whether to make 10 to 20 of this.

thanks for your help


No there are no specific ones i know off, but i usually use one for low pressure in a range like
-0,8-7 bar and one for high pressure in a range like 0-30 bar.

Look for sensors that can take like 30bar max. or so, so that when you have some issues with your
condenser or something they will give reading again when the pressure is within the limits of the sensor.


I just googled and found some transmitters for specific refigurant, but that must be a load of crap because it's just a stainless housing with a membrane and they will work like any other.

hope this helps you


That is very useful information, thanks Kenny!

I kept looking on the net for "specific" pressure transducer but could seem to find any, so I was not sure if I was just not looking correctly or if there was no such thing.

I will follow your recommendations on the ranges and try to find something based on it and my system values.

Thanks again, really useful.


I know I am late,
You can use any over the shelf R134a P/Sensor(NOT SWITCH) as long as you use one that is suited for the pressure you intend to read.
I.E. Low side would be good (higher resolution) for pressures from  zero up to 150 psi, and high side with a lower resolution up to 450 -500 psi. Use the standard R134a "quick connectors" to attach the sensors to the High and Low side service ports.

OR use the sensors on board the vehicle and incorporate your own "Y" connector to utilize the standard factory installed HI/LOW side sensors with out having to "Pipe into" the system.

Don't forget to add a reading for when the condenser fan should come on and to monitor the RPM's for efficiency

You have a Good idea going here


Where would this standard r134a quick connectors be in?
In a car? I don't have experience in car systems so don't know about those connections...
But on a home air conditioner it should be normal 1/4 flare with a schrader(this is in dutch don't know the english word) inside.
If you are to connect these on your home system you will need a copper gasket, but my advice for connecting these things if you don't have experience would be to ask someone who does to take a look with you.

If you can get these readings, it's awesome.
If you get leakage it's going to be expensive to get it filled again if you don't have the tools and

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