The 4.9 with the exploding high-side hose was mine. Made a hell of a noise and lots of smoke.
The stock 4.9 compressor has no
provisions for either switch. Just a blank casting where the switches would be. (As installed in the caddy, it uses temperature sensors that phone home to the... BCM, I think. The BCM then switches the compressor on and off.)
Since the fan (as installed in the Fiero) seems to run whenever the A/C is energized, I'm content to use the pressure/cycling switch on the receiver dryer, and a high-side switch that I am going to add. I figure that the easiest place to add a switch is in series (electrically) with the pressure/cycling switch. I plan to mount it on the high side charge port in the front compartment, when I find the appropriate switch.
The HR6 compressor is supposed to have a physical safety valve to relieve the pressure, if it goes too high. Obviously, my high side hoses had a lower "release" pressure than the safety valve. They really shouldn't have blown first. (Yeah, I know. It's probably a "one shot", and would have scrapped the compressor, but my compressor is shot anyway. Oh well... at least I have new hoses now.
[This message has been edited by Raydar (edited 07-14-2014).]