TCS switch on 4 speed
Team Owner
Joined: Jun 2001
Posts: 23,375
Likes: 1,067
From: Virginia USA
TCS - Transmission Controlled Spark. I can't remember exactly but it controls the vacuum advance in some way. There is other parts to this systems which is a temp sender on the back side of the passenger head and a solenoid on the passenger side of the intake that the vacuum advance vacuum goes through to the distributor. Someone will know more than I do on this.
Pro
Joined: Aug 2001
Posts: 667
Likes: 3
From: College Station TX
Originally Posted by dmrodco
I have found on my 74 4 speed a switch that is shown in the manual as the TCS switch. anyone have a clue as to what it does ?
Basically, the only 2 conditions in which vacuum advance was ALLOWED to the distributor were
1: cold engine (coolant temperature ( < 82 degress ) and on big blocks ( > 232 degrees ) )
OR
2: transmission in HIGH gear ( 3rd on auto, 4th on manual )
So the switch your seeing is a sensor for 4th gear which allows the circuit to go to ground.
and to answer your real question, a properly operating TCS system would certainly hurt overall performance, as well as drive engine temps up. This was the tradeoff of
early emission control systems.
Last edited by sray454; May 19, 2005 at 08:40 AM.
Thread Starter
Drifting
Joined: Dec 2002
Posts: 1,887
Likes: 1
From: Hill AFB area Utah
Thanks That make A LOT of sense now after looking at the wiring diagram of the sensors and switches please PM me a link to the finnish paper I would like to have it for referance thanks
Thread Starter
Drifting
Joined: Dec 2002
Posts: 1,887
Likes: 1
From: Hill AFB area Utah
Yep found it its a smallish rectangle relay looking can on the drives side next to the wiper motor it has two black wires on one side and a few tan wires and a few darker wires on the other side it looks like one tan wire goes to the solenoid on the pass side of the carb darker wires to temp sender I appreciate your help ! 
