GM Schematic 1975: no Silk Purse here

  On the internet I have repeatedly read of owners who are stumped by an electrical problem because the GM schematic in the shop manual or assembly manual is different than what they find on their Corvette. The 1975 Corvette was no exception and I published these differences on the CF but negleted to add them to my own web site. (This is not even the complete list.)
Below is a screen shot, since these do disappear from the ....

04-13-2007, 05:38 PM #1
Doc Rebuild
CF Senior Member

My Corvette Photos
Member Since: Aug 2001
Location: Bridgeport CT

Tip using the 1975 GM wiring schematics

Gentlemen and the few Ladies present:

Let me preface this by saying that my 1975 Corvette a great resource. It was not been wrecked or otherwise modified with one exception. The smog system was removed when new (and is still completely inventories in boxes). However this does not effect any wiring harnesses.

I have recently circuit tested my 1975 wiring harnesses and compared them to the 1975 published GM wiring schematics. Comparing my 1975 I noticed the GM schematic is missing the pink wire in the dash harness for the factory alarm from the rear harness connecter to the fuse box. Whooooops, they all had alarms in 1975. The hood door control switch connector on the dash harness is missing one wire: three needed on 1975, not two as in 1973 and 1974. The passsengers side firewall connector of the dash harness omits an orange jumper wire to the other firewall connector. The yellow lead on the radio connecter does not directly connect with the fuse box. The schematic for an auto trans solenoid accessory harness shows those wires connecting to a (1974 and earlier style) 14 wire cavity connector, instead of the actual 20 wire cavity connector used in 1975. They are vasty different and you cannot connect a 14 & 20 connecter together. And the wires aren’t even in similar spots. A carb idle solenoid connection is shown, but none have been discovered in my garage, the World or Oz to date. The fuse box illustration omits the power accessory terminal identifications as well as the fuse rating. There are actually two different dash wiring harnesses on 1975: one automatic and the other 4 speed. The GM schematic only shows the latter 4 speed, and thus the 75 percent of 1975 owners with automatic can only guess about those 2 automatic neutral safety switch connectors on the dash harness.

There’s more, but I think you may get the idea. May all your sparks be right on and not crossed. There is nothing worse than a dim bulb, unless you are a Luddite.

Geoffrey Coenen

PS If you know more, I’d be pleased to examine and include your findings. If however you are located in the State of Denial, (Illinois) or a Disciple of Daun (Olsen), please accept my apologies for interrupting your nap or alumibeer festival.

Caveat Emptor: Colored In Sows Ears
This is typical of every model year AIM schematic I have studied in detail. They just don't follow what you actually find in the field. There apparently is no shortage of these new sad Colored In AIM schematics on the internet. They are not even a close reference to what you will find on a real Corvette.

    It is, what it is. And oOSOEZ is it.

    Back to Current Events