Stock 72 wiring Questions...

[suburban99]

Hey all, finishing up my LS 6.0 swap and I found these 4wires that don't have my tag...so I missed them during the removal or they weren't hooked up...i think the large red one is for the charge guage...there's a large red, blue, brown\ white, and a black...they pass into the cab thru the grommet in the firewall, except the brown\ white it connects to a plug near the grommet...thanks

[71CHEVYSHORTBED402]

Mine were attached at the junction block on my 71. This may help, but it's worth confirmation. I think you're looking at TCS and a charge wire. Most TCS have been removed. Word is they're mostly worthless.

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" head 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). NOTE: The screw threads are the same as a common "self drilling hex washer" screw.

• 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 plastic boot connector.

• These wires use a retainer mounted to the transmission using a 1/4" head machine tap screw. The hole location is approx. 6" from the end of the boot. The screw thread is #10 x 5/8".

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

Other than that, 12 AWG red should be charge. Mine was: • 12 AWG red & fusible links configuration: A red wire runs from the firewall block to a splice. This wire is soldered with three additional 12 AWG red wires. One wire routes to the alternator, one wire to the voltage regulator, and one wire to a fusible link that attaches to the junction block. NOTE: The red wire from the firewall block also uses a fusible link near the splice.


TS means truck side. Incidentally, "Vette" is a GREAT source for wiring descriptions.

[suburban99]

Thanks Tony..Got it done..