quote Originally posted by olejoedad: You need a shop manual! The C500 connector lives in front of the passenger side strut tower. The engine harness and tail light harness plug into it The C203 connector lives below the ECU, the top part is white, and the bottom two pieces are black. Rather than replace the entire harness, I would clean up the looming and repair what you have. If you insist on replacement, be aware that it will have as many miles on it (or more) and will suffer the same or worse problems. Every Fiero harness I have disassembled, no matter the miles, has been in very good shape inside the looming. The problems arise in the exposed wiring areas and with broken connectors.

Thanks Joe, I already have a shop manual. I've got an 84, an 85, an 86, and an 87... all reprints except the 84. I use the 85 one for pretty much everything on the car. We just haven't gotten to that part yet and didn't feel like looking it up since we were already talking about it, and it's in the garage.

The wiring is unfortunately a mess though, and that block has already been removed several times before we got the car. It was all working though, to be fair. There's rust in the top frame rail, so it all has to come out anyway as we repair that and weld in a new battery tray as well. We're probably... well, definitely giving this car a lot more attention than it's probably worth. The guy who owned it did a great job maintaining it... but again, it has over 200k miles on it, and it's just tired. Most people at this point would have just junked it, but like I said, this was an opportunity for me to teach my daughter a valuable skill that can help her be more mechanically inclined.

I won't be replacing the harness, as this is a mostly stock rebuild, but as part of the restoration, we're going through the entire car. I am replacing several of the connectors that have gone bad or where the clips have broken. I am also not a huge fan of how the factory wiring was laid out across the engine. I know some people will fuss here, but when these cars were built, the harness came with the engine from the factory that assembled the motors, and done in a way that was the most cost-effective, and the easiest to install for the line technician.

I'm more interested in functionality, and improving where the wiring goes. I'm steadfast in the idea that no wiring should protrude down through the front of the motor... I mean, unless it's got a crank reluctor or timing wheel or something. There's no reason (for example), why the A/C compressor harness needs to go down through the center of the motor. I can significantly clean up the motor by getting rid of the black plastic conduit.




Even the bolts on the coolant block-off plate (where the water pump would go in a longitudinal installation). We plan to replace the studs with actual similarly rated bolts once we know that we don't need the actual studs in there for anything. I want the motor to be as clean as possible, and uncluttered. I'd like for everything that's connecting to the motor, to come in through the back of the engine (where the engine and transmission meet), protruding off the firewall and attached right above the bell-housing. Basically... the factory location where MOST of the wiring goes, but I want all of the wiring to go through there. For the A/C compressor wires, I plan to run them under the exhaust manifold shielding, and affixed to the block through little wiring brackets like exist in the front.

I bought several of these, for both mine and my daughter's Fiero...




Anyway, we plan to go through the whole harness, lay it out on thee engine how we want it, resolder all new factory plug-ends, replace some wires only if necessary (and use the factory colors), and then bundle it up with wire loom and shielding tape in the way the factory would have. I want it to look good as well as functional. We're also upgrading to all serpentine, and the newer V5 A/C compressor as well.

Like I said, this Fiero... it was at the point that most people would have junked it. But it ran (meaning the engine was rebuildable), and it was "complete." Which is saying a lot... because Fieros aren't really in the junkyard anymore.

quote Originally posted by theogre: Is Very Likely Part or Why GM Stopped wiring the Alternator thru C500 (or C100 for other model lines) because bigger wire have bigger "pins" & need another Air/Hydro Crimper for installing this costing more to make @ factory. This is Why many say crimp then solder "pins" & other ends that have high current or need very accurate signal but most installers have no clue how to solder right & make a mess.

This is what we're going to do also. I've already repaired the coil to ignition coil harness, and soldered in new pins for the connector replacement (clip was broken, and it was held on by a zip tie).

[This message has been edited by 82-T/A [At Work] (edited 06-03-2024).]

quote Originally posted by 82-T/A [At Work]: Before I go "ape" with the dialectic grease... Ogre... when you said, "That's said, I keep pushing Permatex Green label Brake Grease because is Plastic/Rubber Safe & won't run or wash off easy when used things like ground bolted to the block." Where specifically did you mean you use this? Externally on the block grounds, or are you saying you pack the weather-pack connectors with this? Is this what you use as a replacement instead of the stuff that Joe mentioned that came from the factory in those connectors?

Can use PGBG on many connections... Examples:
Grounds bolted/screwed to anything.
+ wires to the dist block under C500.
Dash back where bulbs & gauges connect in https://www.fiero.nl/forum/Forum2/HTML/146784.html Fuel, Engine Temp or Oil Pressure gauges have problems?

Even if the brake grease hold dirt some, stop that getting @ the metal.
Deoxit etc may work "better" @ some points not others plus use PGBG as indented & cost way less.
Example: Deoxit may work for dash backs but not grounds bolted to engine or frame because too wet & big Voids to hold the "water" that PGBG prevents.
I use so little grease often can barely tell is any there so can't hold a lot of dirt on most things. Grounds bolted to X use more to fill Voids more so on engine "grounds" where many have "lock washers" in the terminals.

You Don't what them on the Outside of Weather Pack or anything else. Most times you don't need it on the Weather Pack "pins" too. Might help only on silicone rubber seal like big one on MAP plug that often get damage from unplugging over the years.
If you have a WP plug in "weird" places allowing "water" to sit then can use the Release Tool to take apart then coat the "pins" for added "water proofing."

But problem is Old WP Plugs can break when you unclip the back cover & many bodies are very hard to get even from Dealers 30+ years ago now 0% available for many plugs.
Other plugs like newer Metripack Pull to Seat are very hard to release even w/ right tool & now how to work w/ them. This "new format" is what the new ECT of ECM is & why only sold to most buyers as Pigtail Kits.

So many times I only recommends most can only spray Plastic Safe connect cleaner w/ lube from CRC etc in the pins then push the plugs together a couple times. the cleaner & small amount of lube left should even coat the "back" you can't see w/o taking them apart. Or try Deoxit etc & follow directions on them.

I have two 2oz tubes of PGBG that only got 2nd because couldn't find 1st > 10 years ago. Older is likely 30+ years. I still have both them because you need so little even on most Brake Jobs. And I use this way more then said here. Just don't use it on Food or Plumbing equipment. Would lube them but likely Toxic. (Can get Food Safe Si oil/grease from Restaurant stores, as plumber si grease, etc.)

[This message has been edited by theogre (edited 06-03-2024).]