Engine Harness 65 GMC
 

In a way its kind of nice that GM has each section of wiring having its own connectors. So the light harness is separate but to get power to the horn relay it comes from the engine harness correct? How many of the wires besides the Alt wire do I need going into the cab from that section?

I am switching to a carbbed LSx engine which will be run off an MSD 6010 box and it has its own wiring.

Speaking of the Horn Relay can you recommend a replacement since the one wire alt will be putting out 140 amps and I would rather be safe than sorry.

Re: Engine Harness 65 GMC
 

The horn relay is nothing but a relay for the horn and a junction for the alternator,battery charge wire, cab power and the regulator power wire. None of these wires is fused by the way.

What I would recommend would be to get a junction and run fusible links from it or a fuse panel which you would run the alternator wire (upgraded to an 8 gauge wire for 140 amp, also not a one-wire but an internally regulated three wire alternator, I.E. CS 144.)

The conversion is simple and you can do away with the low amp alternator and regulator you now have.

The cab only requires one power wire from the horn relay junction as you can see in the diagram below. It runs through the cab connector in the lower right on the diagram and I believe it is in the lower left on the firewall. It is not the alternator wire but it takes the power from the alternator and the battery into the cab.


Attachment 1553901

There is much more you can do to upgrade your truck and we will be glad to help you. You can learn a lot by surfing the 65 truck forum if you haven't already. VV