This subject has been mentioned a few times on the forum but I have found no answer. The TCS relay mounted on the firewall has four male contacts. I know that the double plastic connector with blue and green wires fits on the relay only one way. There are also two single black plastic connectors with black wire and pink stripes. One goes to the TCS relay but which contact? I can't find a schematic that shows which terminal does what. There is another black wire with pink stripe with a black single connector. Mine is taped to the harness behind the wiper motor. It is the TCS jumper harness connector . Both black wires with pink stripes go to the same location electrically on the firewall connector. Where does this TCS jumper harness connect to or does it remain unconnected? Since the TCS systems are often disconnected I can't count out the possibility of a missing wire. Thanks for any help. Bill Gould

 

It may not make any difference, but 350 or 454?

 

lt1 350

 

see if this discussion of the same topic helps
https://www.corvetteforum.com/forums...on-a-70-a.html

this is for a Nova
http://chevynova.org/1970TCSRelay.html

another source
https://www.google.com/search?q=1970...=1524147681775

 

Looking more closely at the 3961573 TCS relay there are 4 terminals but two of them are the same electrically. The double plastic connector plug with the green and blue wire fits only one way on the relay due to its shape. One of the two black/pink wires must plug onto one of the two remaining common terminals on the relay. My original question is what is the TCS jumper harness connector for? Mine is factory taped to the wiring harness and I think should remain unused.

 

Hi Bg,
Might this be of some help?
Do you have the solenoid that's mounted on the right side of the intake manifold in place?
Do you have the TCS connections at the transmission switch, and temperature sensor in the right side head?
Regards,
Alan



The connection at the TCS solenoid. (Not an LT-!, but the same solenoid and connection.)

 

Alan, Yes. I have all of that, The car is apart and I am installing parts piece by piece. I want to be sure that the wiring is OK.

 

Hi Bg,

"My original question is what is the TCS jumper harness connector for?"

Is this connector for the temperature switch what you're asking about?
The short lead is part of the engine harness. The long jumper to the temperature switch is a separate harness.
The lead near the heater hoses only extends out of the harness a few inches.

Regards,
Alan

 

looks like my 70 el camino setup

white plug to vac sol
2 brown wires to head temp switch
relay on firewall.

 

The TCS temp sensor in the right-side cylinder head has TWO sensors in it: one is to sense a MINIMUM temp at which the TCS system will activate; the other is to sense the MAXIMUM temp at which it will DE-activate.

So, the TCS system will not be functional unless the engine is above at MINIMUM temp and it will DE-activate if the engine temp is too high.

As a result, there is a "loop" of wire that connects the two terminals on that sensor. If you remove the connector, that "loop" may appear to be unnecessary; but the ground for that sensor is the metal body of the sensor-to-the engine block. BOTH terminals on that sensor are active, so they are interconnected.

Also, the TCS system was only put on the 'base' [standard] engine. Optional engines required that A.I.R. pump and/or other emissions systems.

Lastly, if you aren't prepping your car for being judged as "original condition", you really should bypass the TCS system. You can leave it in place...but make it inactive and run your distributor vacuum advance can to a "manifold" vacuum source. The TCS system (when active) defeats the vacuum advance system so that the engine timing is retarded; this causes the idle quality to suffer, the engine to run "hot", and uses more fuel. It does nothing GOOD for the engine. It merely reduces SOME hydrocarbons when car is at idle of is in lower transmission gears/ranges.

 

Hi,
I believe you'll find that the TCS system was installed on all 1970 model year cars regardless of what engine the car was equipped with.
Also, that during the 70 model year only the LT-! engine was equipped with the A.I.R. system.
Regards,
Alan

 

Only three of the four connectors are used. The lower aft contact remains empty.

Once you install the entire TCS system and have it functioning, you can simply unplug either the Transmission Switch or the Solenoid (on the manifold) and you will get full time manifold vacuum to the the distributor.

 

First post on these forums, desperately seeking advice!

i installed a new engine wiring harness on my running and driving 1974 coupe, 350. The ONLY thing that is different is that, whatever hack had owned the car before me, had spliced different wires together, and somehow, whatever wires that were spliced and went to the Tcs sensor in the passenger side head was clearly incorrect, but the car was running.

Now with the new harness installed, the car cranks but will not fire. It’s actually popping fuel back up through the carb as I’m trying to start it?! Almost like it’s completely out of time, but I didn’t touch the timing. Nothing else was changed. The plug in the head is the only part of the tcs system still in the car, I have no solenoid on the manifold and never did. Would this actually stop the vehicle from starting? How can I bypass this or run a jumper? I am totally confused!

 

bill I have a 1970 do you have the tcs control on the gas pedal, there are wires that go to it part of the engine wire harness

 

Did you notice that Bill posted in 2018?

 

I hope he still have the car