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Questions on new manifold gauge set. usage

jbrinker on Thu June 21, 2007 1:56 PM User is offline

Year: 2002
Make: Jeep
Model: Grand
Engine Size: 8
Refrigerant Type: 134

Hi all,

I decided to buy a cheap set of AC manifold gauges, a can tap, and have access to a vacuum pump. I have eyeballed these gauges, and understand in theory what Im supposed to do, but Im clueless about a couple things.

#1 - the adaptors that go on the ends of the hoses to attach to the car. They have a "valve" - sorta a knob, that looks like it depresses a pin. I assume this can be used to "close" the schrader-type valve on the car by UN screwing it? Is the best/standard procedure to just "leave it screwed in and push it on quick-release style"?

#2 - the manifold block has TWO connections for the yellow hose. One pointing down seems to be wide-open (just a fitting). One pointing toward me seems to have a schader-type valve in it. What's that for? How or what would I even use it for?

#3 - there are a couple of "dead" connectors on the sides of the manifold block. These are for storing the adapters? Not sure, there are no holes in them so they can't be real "connections".

Any help is vastly appreciated. I plan to do this work in the next day or two.


Oh, heres a pic of the gauges:

(Yes, I know they are CHEAP, but if I get a few uses from them I'm satisfied.) You can see that double-connector on the center port.


mk378 on Thu June 21, 2007 2:36 PM User is offline

#1 You should not screw the knob down until the quick connector is locked on, and also turn the knob back to retract the pin before uncoupling. This will close the shrader valve in the car first and minimize loss of refrigerant.

#2 Not sure about that. Maybe if you had an extra hose you could connect a vacuum pump and a supply of refrigerant at the same time.

#3 Yes those are to park the adapters when not in use.

Evacuate your new manifold before connecting it to a car for the first time, unless of course the car is up to air anyway.

jbrinker on Thu June 21, 2007 2:49 PM User is offline

OK, I think I have this figured out.

And from reading it seems that extra port is exactly that - to connect a can at the same time as vac, thus not introducing any air when charging. However, I don't have an extra hose... So now I wonder if these will even work for me! I will have to try and see, but I fear that if I connect the yellow hose to vac, and pull a vac on the system the schrader valve will surely open (due to pressure from the atmosphere) letting in air... It came with no "cover fitting" to seal off that port (at least none I see).

I guess one plan (not a very good one) might be to:

Car is at ambient pressure/discharged.

Connect blue hose to car. Connect yellow hose to vac, red hose to "Extra" service port, and leave quick connect closed (sealed).

Vac out car, through low side.

Close all valves, connect can to service port. Open high side hose a bit, open can a bit, and purge high side hose and manifold with 134. Close hose/can, close high side manifold valve, and attach high side to car.

Open can tap, open low side manifold valve and charge 1st can.

Start car, and contunue charging until Ive got 28oz in (factory charge).

Close valves, check pressures, etc.

Sound good? Someone please tell me if I DONT have to worry about that schrader valve in the service port....


johndmoon on Fri June 22, 2007 8:51 AM User is offline

Red and blue valves need to be open to pull vacumn on system. Once you pull the vacumn, close valves and do not loosen the red or blue line or open the valves on the manifold guage. This will just let air back into your system. Connect can to yellow line, pierce, then slightly loosen yellow line at manifold guage end so refrigerant purges air out of the line. Tighten yellow line then open blue valve on manifold to start letting refrigerant into low side, and you sound like you know the rest from there. Don't worry about that schrader valve on the manifold guage. Hope this helps - I'm a "newbie" also!


Bob K on Wed October 03, 2007 12:40 AM User is offline


You appear to have the same manifold gauges that I do. Where did you get the piercer for the referigerant cans? Does it mate properly to the yellow manifold line?

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