Does anyone have any experience with this relay used on a 69 442. It is the relay located on the right (pass) fender and is wired in with the Compressor feed. It is called a 'hold in relay' and has two leads coming to it and one coming out to the compressor. Three pronged relay. This was the one relay missing from the car. I finally found a listing for an AC relay with the correct configuration, but I would like to know what it does, before I buy it.

Ross

 

I have heard some years of cars wired so the AC compressor is held engaged a few seconds after the engine was shut off, to reduce the chance of run-on or dieseling.
Not sure if yours had this 'feature' or not, but a possibility...
The 72 had no relay in the compressor circuit.