firewall wires

[71CHEVYSHORTBED402]

Originally Posted by randy500

Pretty sure that's transmission controlled spark wiring. It connects to a relay adjacent to
the upper right of the fuse block.

I agree. Here are some notes for what was on my 71 truck. Might help.

NOTE: TCS is also known as Idle stop or Combination Emission Control.

TCS unit descriptions: There are two units on the firewall, one on the LH (TS) the other on the RH (TS). I believe the unit on the LH (TS) is the RELAY ASM CONT SW. It's the smaller of the two units. The unit on the RH (TS) is the RLY ASM TRANS CONT SW DELAY.

NOTE: These instructions are for the relays in a mounted position:

TCS Assembly:
• The units mount to the firewall using two 3/8" tap screws. The screw threads are 1/4" x 5/8". The bracket for the LH (TS) goes on top the bracket for the RH (TS).

• The "tab" on the LH (TS) unit indicates the top. This may be to help secure the connector. The two pins indicate the bottom of the RH (TS) unit.


TCS Wiring:
• An 24 AWG brown/white striped wire connects at the RH (TS) portion of the firewall block. The end of the wire has a connector. That connects to a connector with two brown wires. The short wire connects to the bottom pin on the RH (TS) unit. The long wire runs to the idle control solenoid.

• A 20 AWG black wire runs from the bottom pin of the RH (TS) unit to the boot connector at the transmission. The connector at the unit includes the brown wire explained above.

• A connector with two 18 AWG dark blue wires plugs into the top pin on the RH (TS) unit. The shortest wire plugs into the bottom pin on the LH (TS) unit. The longest wire routes to the idle control solenoid.

• A 24 AWG brown/white striped wire plugs into the top terminal on the LH (TS) unit. This wire routes to the idle control solenoid. NOTE: The connector at the pin includes a dark green wire that's been cut. I do not know what this is for.

TCS wire routing: The wires to the idle control solenoid route through the firewall gutter and along the retainers on the LH valve cover.

Wiring for transmission: The 18 AWG black wire from TCS and the orange wire for the kick down switch connect at the transmission using a boot connector.

Some information: http://67-72chevytrucks.com/vboard/s....php?p=7037666
http://www.bangshift.com/forum/forum...-switch-wiring