some wiring help

[blazinzuk]

Okay I bought a 89 blazer to use the body on my 73 (eventually) I am having wiriing probs with my starter and other things on my 73 would it be much of a hassle to switch the engine bay harnesses. I haven't even looked at it yet just thought about doing it tonight. Yea or nay

 

[dyeager535]

There are some differences, but I'm not entirely sure about the main engine harness portion. The headlight connector would be different (wiring-wise at least) as would be the wiper one. Since you don't need the ignition stuff, that could just be tucked out of the way (don't cut, if you want TBI later, it's there) and adapted to the plugs you need for the earlier HEI distributor. The starter wiring didn't change. Essentially, all GM did as I think about it, is take the basic harness from 1973, and add things on as needed. (electric choke, wipers, dual headlights, etc) The only difference in all those years in actual wire routing for the engine, would be distributor, at least that I can think of.

It would be better to use the '89 wiring harness (interior+ engine, etc) IMO. There will be a few things you don't need on the later harness, but the advantage is blade fuses, with a bunch of accessory terminals for use to run other items. Besides the fact the newer wiring is going to be in better shape all around.

Also taillight, fuel pump/sender and rear window wiring (if present) have different connectors.

This will add a few more issues (mainly column that I can think of now) but in the end my opinion is that the newer wiring harnesses are superior to the old ones.

Yes, rewiring is a hassle, but swapping bodies is the time to change it.

 

[blazinzuk]

The body swap aint happing for a while. I just need to get my 73 running so I can go wheeling. I haven't really been running in about 2 years so my plan is to take what I need and wheel my truck for a year or two and then swap the bodys

 

[dyeager535]

At some point GM added a cover over the firewall connector, but I think the connector body itself stayed the same. What you'll need to do is compare where the wiring from the '73 engine harness portion of the plug goes, and then check the pins on the '89 to see if the ones you need go to the same places.

Since the plugs are 3 piece, the engine one is the only one you need to deal with. I will add that since I don't have a vehicle that late, I'm only going by memory on ones I've seen, that the plugs will be the same on the firewall between a '73 and '89.

 

[K5 rockcrawler]

I would think it would almost be easier to go ahead and swap the body right away. Other wise you are going to have to adapt the wiring twice. I swapped everything from a 88 to a 78 body. That is the other way around but it wasn't too bad. Now my 78 has TBI 350, 700r4, and a 208 along with the stonger frame.

 

[JDNobodi]

The connectors at the firewall are different. I know the 73 and 74 has two connector plugs while the late seventies have three. I not sure when the change happens, but my guess would be 76. I rewired my 74 with a late seventies harness. The only part of 74 wiring I kept was for the head lights, and I switched the wires from the early plug to the later plug. The engine bay I rewired with new wires.

Oh yeah, even though the plugs are the same between the 73 and 74, they are wired a bit different. I change the engine harness in my 74 with a 73 harness, (before I rewired the whole thing) and I wasn't getting power to my starter. Turns out GM switch the wires for the starting circuit with the fuel sending circuit among with other wires between the two years.