minipete

I have a 1986 GM Shop Manual and Electrical Diagnosis Supplement.

I have difficulty find things in there, it has a great amount of information but doesn't seem to have a useful index or glossary.

Every time I try to find something in there I spend hours reading and going down dead ends.

The wiring diagrams don't seem to have a legend of abbreviations so that is guesswork.

Is there a process to using these manuals that I am missing?

Pete

1985 Corvette

Is there a particular electrical circuit diagram you’re trying to decipher? The diagrams are to give you the basic idea of how the circuits are created. For example, if you’re looking at a diagram for the starter, that diagram will include colors of wires, connection locations and so forth. The last page detailing a particular circuit diagram in the FSM has a legend of the splice locations, grounds, connectors and various other details with brief descriptions of where to find them.




Is it the layout of the picture that’s confusing like the above? A “c” with a number means a connection number. Look at C237 just above the Overdrive relay for example. One curve indicates a male connector and the other curve is female (the curve closest to the bottom of the picture of the two). The convex curve is the male connector with the concave curve indicating that side is female. Also note the “G”, this means when you look at the connector under the dash, the cavity of however many in the connector are visibly labeled with letters. You would want to find “g” printed on the connector and correspond that letter along with the given wire color: “PNK/BLK” which means a pink wire with a black tracer line in the middle to help identify it easier in a bundle
of wires. You should see that wire color combo going into the G cavity of the connector.

So if you got under the dash and looked where the legend tells you to for C237, you would find the female plug is tied in directly to a S109,
which means a splice location where multiple wires meet and are combined to share current loads. In that slice, you would find two pink wires which both have tracer black lines on them heading in the same direction to the overdrive relay. Again, you can see the concave curves on the OD relay where the lines terminate into, meaning that connection you would find at the OD relay will be female, while the OD relay will be male (several blades protruding out for the femal plug to connect to). This also shows you those two wires are in cavities C and E of the female plug.

Hope that helped some.

WVZR-1

Is your car a RHD correct conversion?

65Z01

You need to step-wise work your way into the detailed are of interest.
Start with the major overall index, then the area index and so forth.

There is an index into the electrical area of interest. Then you need read the schematic to understand sub-system operation.

Sometimes the www can be of good value in working on a given issue.

Kevova

Section 8A is electrical diagrams. There is a index of of sub sections in 8A-1 there are illustrations 8A-201 connector plugs 8A-202.
Depending on what you're working on, you may need to refer to the other manual. Section 6E is driveablity it has several sub sections. It's possible to follow flow chart and need to refer to electrical manual as you go. The more you browse manuals the quicker you will learn how they work. Electrical manuals don't include how to access or replace components. That's in "the all but electrical diagnosis" manuals. There was a electrical diagnosis supplement that would come out after the FSM final editions were printed. It's worthless by itself. It only had updated pages that went along with actual 8A of the Final edition FSM. Supplements usually were less than 50 pages.

minipete

Thanks for the detailed response.

I am not really looking for anything in particular now my IAC problem has been sorted but I bought this manual to help me solve problems and I ended up going to old faithful, youtube for answers when I couldn't find it in the manual.

My comment on the legend for the wiring diagram wasn't because I didn't understand it, it just seems funny not to have a legend for a diagram with so many abbreviations.

I would like to better understand the structure of the book so it can be more useful in the future.

From the responses it seems like it doesn't have a useful index. I might just make one myself on a spreadsheet. It will be time consuming but I'm sure I will learn a lot.

There are some more good tips from you guys I will explore first.

My car is LHD btw.

mtwoolford

This may not be to everyone's liking, but I use little "sticky tabs" to mark pages that I have found useful / relevant.

playsdixie

mine is full of "tabs" marking the places I finally found.....when you get done.....post it.....it'll be appreciated.....

minipete

While in lockdown I have been working on the index for the FSM and will post it when done.

I am now trying to decipher the wiring for the overdrive.

The wiring diagrams have components at the top and bottom of each page with the wire colours which is great but if you follow the wires they go to the right hand end of the schematic to blocks/connectors (?) that are unlabelled except for some having 3 digit codes mostly starting with a 4.

I need to know where these wires go?

minipete

In case anyone has been there before me or knows the common colour coding

Relay has
Pink/Black - connects to overdrive solenoid when relay is activated - ignition power?
Brown - is marked .8 BRN-903 (MAN) and goes to a connection labelled "N" - earth?
Dark Green - to overdrive solenoid so I assume when this is powered by the relay it activates the overdrive
The next 2 energise the relay (according to the diagram)
Pink/Black - is spliced to other Pink/Black wires so this maybe ignition power?
Tan/Black - connects to position 422 along with other wires so maybe earth?

I don't want to play with the wiring based on assumptions in case I am wrong.

Anyone?

WVZR-1

Here's 1986 diagrams that might help you explain for someone with an '86 - Circuit #s and color ID are in charts in your FSM in various places. Maybe as many as 3. If someone with an '86 stops by they can maybe use this information to help you. @ihatebarkingdogs if he stops by has an '85 but might be very familiar with '86 also.

minipete

I wish I could find stuff in the FSM that quick.

I have found chart C-8B in my '86 FSM and it tells me where the wires go to.

I want to disconnect the black/tan wire to see whether the overdrive switch is my problem (OD won't switch off).

Thanks for the quick reply.

WVZR-1

This one?

minipete

That's the one.

I disconnected the plug to the OD relay and no more OD which Is what I wanted. I was worried it might throw a code up but it didn't.

My intention is to take the tan/black wire which goes to to the OD control in the ECM and put a switch inline so I can disable the OD when I want to.

RWDsmoke

I agree about the manual. I have a manual for my 86 and it is very easy to navigate. My 96 manual not so easy. Many things I look for are not listed in the index. It's like the 86 manual was written by a mechanic and the 96 manual was written by a computer geek. For either one It just takes a while to figure out the system.

jazfe

There is a sticky about making the overdrive button just a switch by bypassing the computer. I did this to my 86. I couldn't stand the computer shifting into OD all the damn time. So now I just go to OD on the highway when I need it. I can get you a part number for the on off switch that replaces the momentary switch that is in the car now.

minipete

After disconnecting the OD relay proved successful I figured all I needed to do was stop the ECM from activating the overdrive.

After consulting the wiring diagram I traced the wire that energises the overdrive relay back to the ECU. It is the Tan/Black wire, pin A7 (you need good eyes to see the numbers on the ECU).

I cut the wire and wired an on/off switch in line using T-tap connectors. Mounted switch in the rear cupholder to make it reversible.

When the switch is off (open), no overdrive, 4 speed trans. When switch is on (closed) full factory function is restored.

It works perfectly. Went for a drive on the weekend and am very happy.

minipete

ECM Connection

Switch