MorganRock

Hey all... Is there any reason that an early S4 (87) Central Electrical Panel can't be used in an 86? I have a spare electrical panel that's in a lot better condition than the one in the car, and I'd like to replace the panels, but I don't want to get into the project without knowing it's possible.

thanks

SharkSkin

Possible -- maybe. Practical? Depends on how committed and patient you are(or you may end up being committed -- to an institution ). While they may look very similar, and may even be cast from the same mold, it's a safe bet that there are differences in wiring. What you would have to do is go through, wire by wire, and make the 87 panel match the 86 panel.

MorganRock

well, as a CS major and a systems-type thinker, the first thought is really just, what are the differences in systems? The two boards look the same, have the same relays/connectors/fuses... so really you'd just have to check to make sure the set to set construction is the same, because each set of wires on each connector is going to be the same from MY to MY, but perhaps the layout of connectors would be different... (rather than verifying each wire... which would be insane)

If you look at the thing, the only thing connecting the board to the car is the central 12V rails, and the grounds. Otherwise, everything is Connectors for In/Out - Relays for Crosstalk - Fuses for protection.

3 Central systems, all centrally located and (relatively) easily swapped.. brilliant really, unless you have a leak in the car around there... (d'oh! fixed ;P)

Consider the prospect of swapping all fuses/relays in another car, and you'll see why this system kicks ***.

that said, it looks to be the piece that is different is only the XVIII Relay... which is the Cooling Air Flap System in the 87, and the AC Condensor/Radiator Fan in the 86.

since the two boards are constructed/layed out the same, do you all think that since it's just the relay that differs, that the boards can be swapped with minimal hassle (IE swap the relays, hook the 86 connector to the same connector slots as the previous board, and check relay wiring from the back of the relay out?)

Garth S

Well, as Dave suggested, I think you will end up doing a point to point check on that pleasant tangle of grey wires defining the rear of the block: If you haven't the link, check here (thanks to 928 Specialists) to grab a comparitive look at fuse/relay layouts. I suspect some swapping of lead points on the block rear will follow ...

Alan

Yes as Dave says here is a lot of potential for differences. There were major changes in relays and wiring between some years (89-90) and much less between others. IIRC 86 - 87 was not that big of a change - but there are differences and you will need to rewire for those.

You absolutely need to have both CE panel printouts from the wiring diagrams. You need to know exactly how to read these (not quite so obvious) and then you need to verify every single connection...

Yes you really do... If you are lucky there won't be many changes to make.

Consider this to be like a brain transplant - you need to get it right!
If you get one connection wrong you could melt your loom....

Alan

SharkSkin

Morgan, I didn't mean to imply that you need to pull every wire out of the panel. I don't even think that you need the wiring diagrams for this task, though electrical geeks like Alan and I like to have them around. I have disassembled and re-assembled every bit of my wiring panel -- one wire at a time. I understand what you're getting at when you say "systems approach" -- 24 years into CS myself.

But in this particular case you don't have to care what the system as a whole does, only remember that the particular sub-assembly that you're working with can be viewed as a set of hard-wired instructions on how to route information(and power) amongst various external connectors. From that perspective, it is completely irrelevant what those instructions are. It only matters that you duplicate them within the replacement panel. In fact, you don't even have to know anything about electricity or reading schematics to do the job. All you need to know is how to remove and replace terminals within the board without damaging them.

Just be methodical. For example, start with the fuses. go all the way across the panels, not changing anything yet -- just note the differences. Then do the same for the relay sockets, one at a time. If you can take a high-enough resolution photo of the board and print it out, you can use copies of that printout to note differences. Once you have it all mapped out go back and make the changes. With a printout handy to speed note-taking, I could probably identify any differences in the panels in an hour or less, assuming they were both on the bench to start with.

SharkSkin

BTW I think that the link Garth was trying to point you to was this one: https://www.928gt.com/t-8586fuse.aspx

The link he gave is only for the frameset, not the actual page.

Alan

I would really suggest figuring out the differences on paper.... the CE panel is a mess to trace - I know I tried it - reverted to paper mode. You only need to worry about what's different - you don't even need to trace anything for this - just compare one diagram with the other. For the CE panel this is just text lists!. With a couple of different highlighters - work around the perimeter for the CE plugs, the Fuses & the Relays mark eveything thats the same one color and everything thats different another until you are done... then trace only the differences so you know what has to go and what has to be added.... detailed and painstaking but far from impossible a few hours work I'd say (I'm slower than Dave).

Its also actually likely the plug connectors mostly do the same thing Y-T-Y but individual connections can be different - that's the way it works for the most part...

For those of you who have never seen the back - this is what a late model looks like..

Alan

SharkSkin

And the wiring diagrams aren't?

I was just trying to de-mystify it a bit. Looking at it as a purely mechanical problem might be easier for some -- I know it was for me. I'm still not entirely comfortable with the later diagram style(where the heck is that writeup v.2?) but I too generally would want to start on paper. The problem with that arises if there were some mid-year changes that were not in the diagram, or if the second panel didn't come from the MY car you think it did. Also I think some cars claim to be one MY on the DMV paperwork but are in fact a different MY -- federalization/import confusion...

Alan

Dave,
The next major revision is getting close - I'll send you a pre-release if you can handle about 13-14MB in your inbox. That's for the PDF version. It actually @ about 240 pages at the moment (well on it way to epic status - lengthwise anyway).

Alan

MorganRock

well from the 928GT page, it looks as if i have an 86 and 87 board. and the difference is the one i outlined above... it looks like i'll have to trace everything a bit more when i get back out to TX and actually have the car and board in front of me again (about a month rom now). I was just wondering for previous planning's sake...

these cars are a lot like writing programs... it's really better to have everything planned out ahead of time, rather than trying to dive in and figure it out as you go...

FlyingDog

I have an 85 panel in the garage that I was considering using to update my car to blade fuses. 85 and 86 are the same. I can get some pics of it tomorrow. I have not used it, but was told it was functional when I bought it. If you want it, just pay shipping to swap it for the 87 panel you have.

I just noticed you're in College Park. We could meet up at the next NoVA GTG and swap.

SharkSkin

Alan, that would be great. My inbox can take it -- just use the same address. Thanks!

Rob Edwards

Alan-

If you see this, what's the latest on your electricals writeup- is a version available? I've got enough quirks in my '90 that it's time to tackle a CE cleanup, and I'd be interested to see what you've written (not that I'm in a position to actually understand/follow it...... Thanks!

-Rob

Alan

Rob,
Send me an email address in a PM - can you rcv a 10MB file though?

Alan