Ok, before you say "read the instructions, you need to install the diode" -

I already did that.

I have the diode already installed on the brown alternator wire on my Camaro. It didn't fix the problem? It just started doing this today actually. You turn the car off by turning the key to "off", and everything will shut down, but the engine will continue to run like normal. Now, if you turn on the heater blower motor, it will shut the motor off right away. MSD says this problem should be fixed by installing the diode, but that didn't do it?

Anyone know what might be going on?

 

Do you have an electric radiator fan?

 

I do...

I did solve the problem today though, and I'll fill in here, just incase anyone else has the same issue later.

This happened during a carb swap I did the other day. Everything was cool before I removed my 750 VS Holley, but this problem popped up after I got my 650 Double Pumper installed.

The reason for this! da da DAAAA....

The electric choke. I have one on my 750, but didn't on the double pumper. As soon as I installed the electric choke on the double pumper today, problem disappeared. I guess the choke puts just enough load on the electrical system that the MSD can't keep running on its own after the power is turned off at the key.