Automotive Air Conditioning Information Forum

i used my gauges a few times and noticed sometimes they have freon left in them after i disconnect them
i noticed when i hang them in my room after use the dials bleed down slowly over time

this time how ever the high side is steady around 100 and the low side has blead down to about 5psi
is this normal or do they leak the coup/connectors are closed

could it be the colder temps in my room making the pressures drop in the gauges?

1) pros will bleed the high side hose back into the car's system, since once it has been connected to the car, it is now full of high pressure liquid refrigerant. Also, if you don't bleed back, you are slowly depleting the refrigerant amount in the system each time you use your manifold
2) depending on the quality/age of the hoses they may be permeable to refrigerant, or the end seals may be shot

Gage set hoses come in a very wide range of quality. You get what you pay for in this area. Yellow Jacket or other top brand hoses have a limited life, this life will be very short with cheap hoses, long with expensive hoses. I end up testing my hoses and manifold everytime I have a leak I can't easily find. It's usually somewhere else, but occasionally I'll find leaking hoses and throw them out.

I suggest you cap the hoses by screwing them onto the plugs that are integrated into the manifold, pressurize and use snoop or soapy water or Windex. I would guess you'll find your leak, if the hoses are old, brittle, cracking, just replace

how do you bleed the high side hose back into the car's system?

penguins25 wrote: ↑Thu Jul 15, 2021 10:23 am how do you bleed the high side hose back into the car's system?

There's a little trick to that, but once you know how, it's easy.

Note that this is done only after evacuating a system and charging it. If you're connecting a Manifold Gauge Set (MGS) to test the pressures alone, there will be some air and moisture in the hoses, which you don't want to draw into the system for obvious reasons.

Here's the procedure after evacuating and charging a system, which must be done in this order:

1. With the engine running at a fast idle--about 1,800 RPM--the compressor engaged, and the MGS still connected to the A/C system and the refrigerant container, close the adapter connected to the system's high-side port AND the refrigerant container's valve to which the yellow hose is connected. The adapter connected to the low-side port remains in the open position.
2. Open both the high-side and low-side MGS hand-wheels. The system will quickly draw-in the pressurized refrigerant and oil from all three hoses through the blue low-side hose.
3. Disconnect the MGS from the system and the hoses from the MGS.

i pulled a vacuum on the low side and it does not hold
it very slowly leaks out over time
i think i might of over tighten the low side once could this be the cause?

penguins25 wrote: ↑Mon Jul 19, 2021 9:14 am i pulled a vacuum on the low side and it does not hold
it very slowly leaks out over time
i think i might of over tighten the low side once could this be the cause?

Could be. Maybe the over-tightening tore up one of the seals. Change the seals and/or o-rings inside the knurled hose fittings (common leakage area) and try the vacuum test again. If it still leaks down, it could be the valve stem(s) inside the Manifold Gauge Set (MGS), the adapters that attach to the vehicle's low-side and high-side ports, the connections where the gauges thread into the MGS, the gauges themselves, or the hose(es).

i got myself a 30lb tank of freon and a scale
could you describe step by step hot to charge my system

pull a vacuum on low and high side?
zero out the scale before i open the tank?
stuff like that
thanks

The process is the same as with cans.

pull a vacuum on low and high side - always
zero out the scale before you open the tank
be sure to bleed air out of any hoses that were not vacuumed out using the refrigerant
we assume you know what weight the correct charge is
Once all vacuumed and ready to charge, close the hi side handwheel.
leave low side handwheel open
open valve on jug (engine off)
allow the vacuum to pull in what it will (keep an eye on the scale)
once no more is pulled in, start engine and activate AC in the usual way
allow compressor to draw in remaining amount of refrigerant needed based on scale reading
close jug valve

Once you are satisfied with the system, bleed the hi side hose back into the system thru the low side as previously mentioned by JohnHere. This is refrigerant that was weighed into your system and belongs in your system
The amount of refrigerant remaining in the low side hose is insignificant

Thought you had issues with leaking hose seals or some such problem, be sure all your hose connections etc are leak proof. You can get fresh black sealing sleeves on line or from Tim, for example Yellow Jacket has them about 10 to a package. They have to be changed out periodically anyway

BTW it is not necessary to tighten the knurl knobs to death

Seems to me Tim has a sticky on here somewhere that describes all this better