Where does this harness plug into?

[SS Tim]

Originally Posted by 72 K20

I put a new harness in my 72 and it has the anti diesel plug ,, the old one did not . does it have to be hooked up ? Or do I need to get a relay ? If there isn't an anti diesel solenoid on the carb what does the relay do ?

Thank you in advance ! Have a great day ! Tom

If your "72" replacement harness had the plug it may have been a universal or simply a replacement for 71 and 72 with extra connectors covering both.

Your questions indicate you didn't read the manual referenced. So in a nutshell for 71 GM used the a/c compressor during shutdown to put additional load on the engine to prevent dieseling.

In 72 they used a dedicate idle stop solenoid as part of the TCS (transmission controlled spark) to alllow the throttle blades to close fully during engine shutdown choking the motor vs loading as an anti-dieseling control.

Most people have tossed the system and I see weekly "whats this relay/wire/stuff" posts on artifacts current owner's find.

To generalize most trucks had it and most people are using more advance allowing them to get by without it.