Today, I decided to add some freon (R-134) to my truck, as during last summer it was apparent that the old girl was running a little low.

So I buy the kit at the local Advanced Auto, install it, and add freon, watching the little gauge thingy so I wouldn't overcharge it. According to the gauge, I didn't, even after adding a full 19-ounce can.

So I go in and buy another. Plug it in, and ITS guage goes into the red!

I immediately unplugged it and returned the second can (I was doing this in the parking lot). When I plugged the original gauge in, it also went into the red.

So I drive off, and about a block away I hear a distinctive pop and hiss. Immediately stop the truck and pop the hood. Smells like freon. Oh, oh....

So I bled the system down until the gauge (which seemed to be working fine now) read just a hair below normal (I bled a hair too much.). End of problems. A/C running fine.



So.... the question is, does the A/C system have a safety purge valve to release excess freon pressure? Do I need to top off the R-134 correctly?

Last summer, my A/C could not compete with the 110F+ temps of Laredo, but this is NC, which gets hot, but not that hot.

What brand of truck?

2000 Isuzu Trooper LS.

OK, now that we've established that...

...I have absolutely no idea whether or not your vehicle has a resettable "safety purge valve".

How does the sight glass look? Does it look like you've still got plenty of Freon in the system?

I don't think my system has a sight glass.

Gonna have to dig out the service manual.

Dont use cheap guages to charge your ac with.

R134 is linked to prostate cancer.  A single exposure is extremely dangerous.  Don't be "smelling" it.

I also found that you cannot add freon unless you raise the engine RPM.

Did a bunch of lube leak out?  Perhaps around the front seal of your compressor?  

I just checked Alldata.  You have a high pressure safety switch that will release excess pressure.

Yes indeed, many systems have a purge valve that will vent excess pressure when overcharged.

I've done it before myself,  when recharging a system, a phone rings or I get distracted, and put too much in.  The gauge set reads high, and the "pffffffftttt!" sound of refridgerant bleeding off from the purge valve.  

 Recover a small amount to bring the system back to normal specs, and you're good to go!

Quoted: I just checked Alldata.  You have a high pressure safety switch that will release excess pressure.

Is it a switch, or a valve? Generally, a high pressure switch just interrupts DC power to the compressor clutch, in order to keep it from being damaged - Unlike a valve, it doesn't release any freon.

I agree it has a purge valve thats protects the seals from being over pressurized

Quoted: I just checked Alldata.  You have a high pressure safety switch that will release excess pressure.

Thank God.

Thanks for that info.

Quoted: R134 is linked to prostate cancer.  A single exposure is extremely dangerous.  Don't be "smelling" it.

I'm fucked. I got a whole lot of the stuff.