1991 300-SEL

I know I'm out of refrigerant. R12 is in route.

I dealt with this once on an '87 Accord. Hot-wired the pressure switch connected to the receiver-dryer and that engaged the clutch which got a draw going. Charged thru low pressure side. Worked well.

On my 1991 300-SEL, there are 2 wires coming off the pressure switch connection. I disconnected one and jumpered the 2 female ends - set a fan speed - turned on the compressor by way of push button controller(PBC). Clutch did not engage. I know I'm empty and have no plans to actually do this until I have the R12 hooked up and ready to go. Just testing to see if I can get the clutch to engage to get a draw of refrigerant going thru the low pressure side once I have the R12. As soon as I see the clutch engage, I'll pull the jumper wire. I then tried jumpering the other wire. Clutch would not engage.

I connected a voltage meter to each of these wires. One read about 13.6V; the other about just a hair over 1V.

If I had an issue within the PBC, would it stop the clutch from engaging using this hot-wire method?

Determining where the refrigerant went is for later. The unit has been empty for quite a long time.

Thanks for your time.