Does anyone know what the "switch asm (T C S)" for the a/c? I looked at my picture diagram from my factory assembly manual and it says two wires go to this sensor that goes into the side of the block. Can I buy it and any autoparts store?
thanks graemlins/beers.gif

You need to be a little more specific. The wires go into some kind of sensor in the engine block? What year car/engine/tranny combination do you have? TCS usually refers to "Transmission Controlled Spark"

Its a 70 chevelle 350/350th tranny. I got the picture diagram from Factory Assembly Instruction Manual page 504 "air condtioning wiring".
thanks ;)

anybody know?

I see this in my 71 manual also. Although it isn't clear, I don't think it has anything to do with the A/C, even though the thing says "HARN ASM A/C" quite clearly. Unless the six-banger A/C is different than the V-8? The page this picture is on in my book says "Information Transferred" in big bold letters, so maybe it's not relevant?

When I pulled the motor out it had this sensor/ plug on the side the block with two wires going to it and I do remember pulling off the wires. I thought it was water temp but i had one on the other side. The bad thing is i sent the motor for machine work and forgot to take it off so cant identfy it correctly. I saw it by chance when I was looking at the wire diagram and recgonized it. :confused:

I believe the item in question is the alternate location for the TCS switch. If a Chevelle was equipped with the optional gauge dash the temp sender installed in the driver side. In this case the TCS switch was installed in the passenger side.

I went to the pomona swap meet today and i did see some chevelles with a/c have this "TCS" on the passenger side head with two wires. So i guess my question would be do i need it? If so where can i get one? smile.gif

Originally posted by german:
Does anyone know what the "switch asm (T C S)" for the a/c? I looked at my picture diagram from my factory assembly manual and it says two wires go to this sensor that goes into the side of the block. Can I buy it and any autoparts store?
thanks graemlins/beers.gif Are you sure it's in the block and not in the head ?

its actually in the head passenger side.

TCS and A/C are unrelated. The TCS wires go to a relay on the firewall behind the distributor, with another wire (don't know what color goes where, but I think the transmission wire is black?) that goes to the transmission. The A/C has another relay on the firewall up on top of the heater box...

german

Do you have a gauge dash in you Chevelle?

"So i guess my question would be do i need it?"

I think in California you need to have the TCS system in place and functioning.

No, I just have the regular console non ss, I think the a/c wiring diagram through me for loop from the book.

Just trying to understand why the switch is on the right side. Is there anything in the same location on the left head?

I don't know why it is illustrated in the A/C section of the assembly man. It's in my assembly man also but the page number is not the same (504)290 in mine. If you look at the part # 6489785 and description it's identified as switch asm.TCS

Its toward the rear of the passenger side head and it has one wire to one connection and the other wire is looped to the other connection. part number 6489785 " switch ASM (T.C.S.)" It has a closer view and it says "HARN ASM A/C"

I am pretty sure the sensor that you are talking about is a temperature sensor that is part of the emissions control system. It has something to do with controlling the distributor advance depending upon the engine temp, vacuum and the gear that the transmission is in. The wiring may be part of the A/C harness. Maybe someone else can help clarify this.

TCS is Transmission Controlled Spark. Yes it is part of the emissions system. The circuit blocks the vacuum advance to the distributor depending on engine temp and transmission gear.

The confusion stems from the fact that it is illistrated in the A/C section of the 70 Chevelle assembly manual and identifying the wiring to it as A/C harness.

The illustration in the assemb man is meant to show the alternate location of the switch when the optional gauge package was installed. If the car has an idiot light the switch is installed in the left side head and operates the indicating light and the TCS circuit. If a car has gauges a temp sender is installed in the left side head and the TCS switch is installed in the right side head.

Well it safe to say that I dont need it since Im taking out the smog pump. Like I said before the manual through me for a loop but thanks everyone for responding. You learn something every day! graemlins/thumbsup.gif

You might want to check the emissions law in your state (I've heard Cali is very strict) If you are going to drive the car on public roads, you might want to keep the smog system intact or at least keep the pieces around in case you are forced to put everything back in place.

On the TCS cars, the temperature sensor was a dual unit. My Chevelle had the dual sensor in the driver side head. Half of the sensor was for the temperature light, the other half controlled the TCS relay. Normally, in a TCS vehicle, the only time the distributor had vacuum advance was when the transmission was in "high" gear. There was a solenoid "in line" with the vacuum line from the carb to the distributor which would control the vacuum. However, until the engine reached, I believe, 85 degrees, full vacuum advance was applied. THIS function was controlled by the dual temperature sensor AND the relay on the firewall. This was to improve drivability until the engine warmed up. After the engine reached operating temperature, the vacuum advance operated ONLY when the transmission shifted into "high" gear. On the automatic transmissions, this was done with a pressure switch mounted on the passenger side of the trans. I still use the dual sensor, but am only using the one side for the indicator lamp. The TCS was disconnected when I converted over to an Edelbrock manifold and Holley four barrel. Still kept the parts, though. Never, NEVER, throw anything out!! ;)

thanks for the advice. graemlins/beers.gif