This year for the first time, I notice on EBay these sets of A/C Manifold Gauges that have a "sight glass" feature.

I was aware that you have one gauge for the high side and one for the low side. What the heck is the sight glass used for? There's no orifice or anything in the gauge manifold is there? What are you looking for in the sight glass?

Time for me to purchase a set for R-134 and I'm checking the selection. Any advice or recommendations welcome.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

My $100 ones also have the sight glass. It was good to see if freon was flowing from the can to the car. That is about the only use I could see.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

I believe it is to give you a visual indicator to keep you from putting liquid into the suction line.
John
if you get guages, get a set that has removable 134 ends with 1/4" flare (standard) connectors, so you can use it on 12 and 134 vehicles.
it also makes it easier to use with vacuum pumps.
John

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Question: Don't the R-12 and R-134A flare fittings have different thread styles so that they cannot be interchanged? The R-134A threads I've seen have a courser thread, more like an Acme thread.

r-12 threads and r-134 threads are opposite. r-12 is female. r-134 is male. Meaning you cannot use a male on a male coupler you must find another 134a system that accepts 134a. now female on female is ok.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

OK - thanks for the info on the sight glass.

I thought it was better not to use the same gauges on R-12 and R-134a systems because when you swap spit (i.e. oil) that causes problems, because the oils are not compatible with each other.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

I got my set from autozone, it is a nice manifold with cht chargind hose threaded for the 134tank, and the red and blue lines ends have 1/4" female and there is adapters with the quick connect ends for 134 that have 1/4" male ends on them.
awesome set!
John

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!