1974 L-48 Engine wiring
In the Assembly Manual 12H sheet 6 , there is a TCS Temp switch (12J) 2 prong on the passenger side of the motor just above the starter. My connector is missing and the wire hanging (ASM 7A) has some insulation material still left. I thought the temperature sending unit ( single prong ) is on driver side. My temp gauge works correctly. Any thoughts? Thankyoufor your help, Guenter
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Re: 1974 L-48 Engine wiring
The AIM is correct. The sender on the passenger side is for the TCS system only, not for temperature indication on the gauge. -
Re: 1974 L-48 Engine wiring
Guenter and Mike------
...and that's why the wire is left hanging. Many folks long ago disconnected the various elements of the TCS system to improve driveability. I'll bet that GM had a tough time selling in SERVICE the various component parts of this system. The only thing that "turned that around" was the restoration "craze". Of course, by that time GM had discontinued most of the parts.In Appreciation of John HinckleyComment
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Re: 1974 L-48 Engine wiring
To wit (when's the last time anybody said that) have a look at what Paul Latour is going through trying to restore his TCS
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Re: 1974 L-48 Engine wiring
Dear Mike and Joe,
Appreciate the input and the link to Paul. GuenterComment
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Re: 1974 L-48 Engine wiring
Yes, the 2-prong device on the RH side of the engine is a temperature SWITCH. The single contact device on the LH side of the engine is the temp sender.
Temp sender is a variable resistor to pace the temp gauge in the instrument cluster. The temp switch is a three position device device that tells the TCS: (1) engine is cold, (2) engine is at normal temp, (3) engine is in over-heat range.
It's ususally connected to the engine harness by a single green wire which connects to a 2-pin connector with the two pins 'daisy chained' together. The two pins represent (1) and (3) above resulting in the switches contact closure to ground. Grounding this TCS input tells the TCS to pass vac to the distributor and slightly increase engine idle RPM.
If the engine is cold, increasing idle RPM speeds warm up. If the engine is overheating, boosting idle RPM pulls more air through the radiator to cool the engine down.
If your car is missing that aspect of its engine wiring harness, visit a local scrap yard and look for a Chevy passenger car V8 from the same era whose engine harness is intact. PS, new/reproduction engine harness assy's come with that branch of the system fresh and intact.Comment
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Re: 1974 L-48 Engine wiring
Jack,, Appreciate the detailed description. Always grateful for good advice. GuenterComment
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