Automotive Air Conditioning Information Forum

I was trying to check the low pressure side os the ac on my 2008 Mazda 3 but the gauge set that I have have which is about 15 years old would not read any pressure.
Upon inspection it looks like the Mazda schrader valve sits deeper the the port than the part on my gauge set depressing stud and will not push down on the valve allowing the gauge to read the pressure.
Are there differant low pressure fittings?

Low side R134a ports are all standard in size. It's the high side that is different with R12 systems.

I just checked on my 2005 Jeep TJ w 4.0 it has the same scharder valve depth.
Here is a photo of the LPS fitting in my 15 year old Manifold set and a can to hose to LPS fitting that was included with some cans of r134 I got from Ebay.
Note the locking balls are at the same depth but the plastic LPS has the schader valve depressor sit uo at a depth of the locking ball while my old fitting thr depressor sit down deeper than the locking balls.
I have never needed to add any freon to my jeep.
But had to top off the Mazda so I used the plactic LPS one.

Thanks

Also, make sure that you rotate the thumbwheel on your adapter clockwise to open the port, which is not intuitive.

Do your adapters look like these? If so, they should work.

Here is my LPS fitting

Examine the depth to the depressor when the knob is in the open position vs the closed position.
I have seen the depressor knobs marked backwards.

JPHikr wrote: Sat Aug 16, 2025 10:50 am I have never needed to add any freon to my jeep.
But had to top off the Mazda so I used the plactic LPS one.

I meant to tell you that you can't "top off" a system. Although pressures are good diagnostic tools, they can't and won't tell you the amount of refrigerant contained in a system. It MUST be charged precisely by weight using an accurate refrigerant scale in conjunction with a Manifold Gauge Set. The best way is to recover the refrigerant (or have it done) and then recharge the system into a well-held vacuum.

The specs I have for your car are as follows: 18 ounces net weight of R-134a, and 5.0 fluid ounces of PAG-46.