I am attempting to attach a/c gauges to my original '58 a/c system. It appears that the "hand valves" as called out in the service manual are what's being pointed at in this photo. Anybody have experience with these? They don't want to budge, the heads are 1/4" square and cannot handle much torque. I need to use the gauges to trouble shoot the system but am stymied as they're not Schrader-valve attachments like the newer systems. (I'm quite sure my Hot Gas Valve is bad but hate to pull it without some readings). Experienced thoughts welcomed!!! thanks all.

 

You will need an A/C valve ratchet like this one ;
https://www.ebay.com/itm/Ritchie-Too...UAAOSwImRYVy6h
Attach your guage hoses to the fittings on the side of the valves . Then turn the valve stems clockwise one or two turns to open the system to the guage set .
Before disconnecting the hoses , turn the valve stems counterclockwise to close the system off from the guage set .
Be sure to replace all caps to prevent leakage .
You must use a guage set compatible with R-12 systems . R-134 guage sets will not work .

 

Dedicated tool -- great help and sure hope they're not hopeless.

I've got the right fittings for all 3 connections, but am curious about your R12 vs. 134 gauges. Assume you're referring to the fittings?

At any rate, thanks very much for the help.

R

 

Yes , the fittings for R-134 are different than R-12 .
But , the temperature vs. pressure scale on the guage is different also .
You may have been trying to turn the valves the wrong way .
Clockwise to open the valve , counterclockwise to close it .

 

got it. My gauges have both scales, but did not pay much attention until your post. thanks again. fingers crossed those fittings will budge once proper tool is in my hands.