The pressures are dependent on ambient temps, but in general the high should be in the 120-180 and the low should be in the 20-30 range. Again depending on temp. A hissing behind the glove box sounds like a high pressure leak, which could be the expansion valve, Suction Throttling Valve (if your car came with R-12), or a leaking evaporator (ugh). If the car came with R-12 and has been converted it to R-134 without removing the STV then your problem is most likely the STV. In any case you have to get access thru the interior. Some have been successful going the the glove box opening, for myself I remove the dash for better access.
17:48:03 05/19/23
