Air Conditioning Manifold Gauges

My favorite air conditioning manifold gauges are Digi-cool.

They tell you the pressures AND temperatures for commonly used refrigerants including 410A/AZ 20, and have a bar graph that shows momentary pressure drops and spikes, which gives you an even clearer picture of what's happening in the evaporator and condenser.

You don't have to carry a pressure/temperature card for the different refrigerants out there, because they're all loaded into the Digi-cool software, and you can change the refrigerant read-out with the push of a button.

Digi-cool air conditioning manifold gauges definitely streamline the process of evaluating what's happening when troubleshooting or charging a system, and if you're an HVAC technician who works on a wide variety of equipment and refrigerants, the bottom line is that they'll help you be more efficient.

For more information about their features, pay them a visit at

My second favorite brand of air conditioning manifold gauges is Yellow Jacket.

They can take a lot of hard knocks, and when they finally fail, the manifold has a lifetime warranty.

I've sent two failed Yellow Jacket manifolds in, and was sent replacements that looked brand new, with no questions asked.

That's remarkable customer service, and I appreciate it.

The only reason they're not my absolute favorite gauges is that they're not quite as versatile as the Digicool set.

How do I use my air conditioning manifold gauges?

On a unit that's running, the pressure readings can give you a picture of what's happening in the system.

On the low side, (if the unit is running normally, or close to normally), imagine the evaporator being about half full of cold, low pressure, boiling refrigerant.

Imagine that the suction pressure (and evaporating temperature) is exactly at the top surface of that refrigerant, where the bubbles are popping.

This might not be a scientifically perfect definition of suction pressure, but it's a mental picture that will help you evaluate the overall operating characterisitics of the system accurately and efficiently.

If you have high superheat, the evaporator is mostly empty.

If you have low superheat, the evaporator is mostly full.

On the high side, imagine the condenser being about half full of warm, high pressure, liquid refrigerant, with drops of condensed refrigerant running down the inside of the tubing, and the discharge pressure (and condensing temperature) is exactly at the top surface of that condensed liquid refrigerant.

Once again, this might not be a scientifically perfect definition of discharge pressure, but it's another mental picture that will help you evaluate the overall operating characterisitics of the system accurately and efficiently.

If I have high subcooling, the condenser is mostly full.

If I have low subcooling, the condenser is mostly empty.

For more detailed information about troubleshooting with your air conditioning manifold gauges, see our Air Conditioning Troubleshooting page.

Other tips about using air conditioning manifold gauges:

The new refrigerant R410a/Az 20 is a high pressure refrigerant.

You will need a manifold gauge and hoses rated for the higher pressures.

When evacuating through shraders, if I don't remove the pins, I start evacuating through the low side only, and watch the high side gauge to make sure the hose fitting has depressed the pin enough for a vacuum to go through.

After I've seen the high side gauge drop towards a vacuum, I open the high side manifold valve.

Test your air conditioning manifold gauges if you're using them for deep vacuum evacuations.

Plug either the high or low side hose end, put a micron gauge on the other hose end, put an isolation valve on the center hose end, pull the set into a deep vacuum, then isolate it and see if it holds 500 microns.

If it doesn't, either overhaul your manifold and hose set or start evacuating through copper lines.

I hope this page has helped, and please, feel free to contact us with any specific questions you might have, including questions about air conditioning on Guam, and refrigeration on Guam.

Are you learning the HVAC Trade "on the job"?
If you would be interested in developing your potential to become the finest HVAC Technician you possibly can by studying a complete, accredited HVAC Technician course at home; we highly recommend that you contact Penn Foster Career School and request their free, no-obligation information brochure.
Requesting the information is easy and only takes 2 minutes; and it might be the first step towards changing your whole future.
You'll find a brief review of the course on our HVAC Training page.

Return from Air Conditioning Manifold Gauges to the Air Conditioning and Refrigeration Guide home page.

Share this page:
Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.