[Mr. G]

I just received a new reproduction wiring harness and I was expecting one of the two plugs (passenger side) for the temp sender to have the three prong female plug on the harness but it only has a single prong female plug at that location. The car has rally gauges and I was under the impression that the three prong plug was what was needed for the gauges. Is there a single prong sender that should be used with the rally gauges or did the maker of the wiring harness make a mistake. The car had the 400 motor originally with the three prong temp sender on it. Thanks for any help.

[Kenth]

1971 455HO uses a Thermostatic Vacuum Switch in conjunction with a throttle actuated spark port on carb to control the vacuum advance.

All other 1970-74 Pontiac V8 engines uses the Transmission Control System with the three prong temperature switch for the vacuum advance.

[Mr. G]

Thanks Kenth. Now I see how the system works, but now I need the impossible to find fast idle stop solenoid to make it all work. Good news is that the wiring harness is correct. Thanks again for pointing me in the right direction.