Sending unit mystery for 1972 TCS system - need sage advice
 

Seeking help from electrical gurus.

The GM part number corresponding with a sending unit I need for the transmission controlled spark (TCS) system in an original 1972 350 small block produces units that have a pair of male spade-type connectors for the electrical harness but the original sending unit has a single spade-type connector. The harness has only a single female connector.

Photos of the original single spade sender, an excerpt from the parts catalog showing the number, and one example of double spade sender with the "correct" part number (multiple additional examples exist).

Is it at all conceivable that the original unit was superseded with an example having two connectors and that one of the two connectors would suffice for the TCS system in my engine?

Re: Sending unit mystery for 1972 TCS system - need sage advice
 

FWIW, here is a schematic from the chassis manual that seems to show two prongs at the sending unit (temperature switch) with one devoted to a warning light?

And another TCS schmatic with a single prong sending unit.

Re: Sending unit mystery for 1972 TCS system - need sage advice
 

The TCS system uses thermal switches and relays to roll back the timing and downshift the transmission in a pathetic attempt to control emissions. The two terminal sensor controls a vacuum switch and a relay set to a warning light.
Most of those devices were removed just after clearing the dealers lot. I don't fully understand how they work and I don't really care too. If you are doing a full resto on a truck you can find plenty of info on the net.

Re: Sending unit mystery for 1972 TCS system - need sage advice
 

Thanks VetteVet - I’ve got all the info I need essentially just can’t find the single spade sending unit despite knowing the correct part number and so my question is whether or not a double spade connector version (same part number) would be useful if only the connectors were utilized (ie that to the vacuum) or would this say preclude a complete circuit. It appears as if the single spade senders were superseded by a two spade example.

Re: Sending unit mystery for 1972 TCS system - need sage advice
 

It makes sense that a double would work if you can figure out which terminal to use. The pre 64 years had a double coolant sensor which fed a hot light and a cold light but GM discontinued it in 65 or 66. It's not pertinent to your issue I just thought I would mention it.

With all the discarded systems out there you should be able to find some one with the sensor you need. It looks like the regular temp light sensor on the 67/ 72 years. That wouldn't work though it has a larger range.


Google search on 6489600--
https://search.yahoo.com/yhs/search?...896924%3Aup%3D


Nice truck you have there BTW.

Re: Sending unit mystery for 1972 TCS system - need sage advice
 

Thanks! I'm going to try a 2x connector unit and see how it goes. I agree though this whole TCS system wouldn't be missed but heck I also restored the missing A.I.R. system too. Seems I'm a glutton for punishment.

Re: Sending unit mystery for 1972 TCS system - need sage advice
 

Kudos to you for your goals, it's really hard to do a complete restoration on anything really, especially that old. It will pay you dividends in the future I'm sure. VV