Review on Pro ACP410 4 Hose Dispenser by Robert Blanton

I checked the pressure last night and it was just under 30psi. I was given a can of R134a to refill and the next morning before I hooked up the can I decided to check the pressure again. This time the pressure was only about 40psi, a jump of 10psi in 14 hours. Disconnected/reconnected again and the pressure again showed about 30psi. Not sure, decided to squeeze a little R134 but it wouldn't release the freon from the self sealing can. After some struggling, the canister was hooked and now, after reconnecting the gauge to the machine, the pressure had risen to 45psi, although the Freon metering trigger had not yet been pulled. All of these pressure readings were taken with the engine running, A/C at maximum cold, and circulating on. Due to the fact that the pressure gauge is everywhere, and the pressure reading fluctuates, I decided to do without it altogether. Luckily I did as the HVAC technician was working outside the house the next day to check the pressure and it came in at 47psi and based on his calculation of the ambient temp the car didn't need to be charged. Maybe the sensor was defective or miscalibrated, but you wouldn't know unless you had something to compare it to. This may be the case with all such sensors and I would not trust any of them. Proper inspection protocol must be followed for both the low and high side for reliability and peace of mind or you risk damaging your air conditioning system.