73-87 Chevy _ GMC Trucks > Blazers/Jimmys

Restoring 74 Blazer


Need help on some wiring.......The Tach has 3 wires brown, black and red  red and brown are cut and go nowhere.......and I have about 4 wires left over in the engine bay coming out of the firewall.i know one is for the fuel gage and one for the thermostat but which????  any help thanx........

Do you have a factory tach?  I put an aftermarket one in my truck and it had 4 wires.  Red was battery, white was gauge lights, green went to the distributor, and the black was ground.  If you have a factory tach built into your dash then the gauge lights wire is out........leaving in my opinion:
Red - Battery
Brown - Distributor
Black - Ground

I believe that the gas gauge wire should be wired into your engine wiring harness and is not a separate wire that leaves the cab.  A green wire should run to your temp gauge (but chevy sometimes uses whatever they have  )

My best advice is to get a multimeter and test wires as you go.  If you look at the back of your instrument cluster you should be able to trace the circuit from the gauge to the connection.  Then using the meter (and trial and error) figure out which remaining wire connects to what.  I have a factory wiring manual at home for my '73 (at work now) which should be the same as your 74.  If you still cant figure the wiring out let me know an i can scan the wiring schematics for you. 1973 K20 - 350/350/205Edited by: 73K20 at: 1/13/03 5:30:15 pm

yes it is an origanal tach .I will check the wires out


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