So, in my daughter's 1985 Fiero 2m4 SE, I've noticed that the way the engine wiring harness was installed, I have to assume the reason it was done so is because the engine was provided as an assembled unit with everything already installed onto it at the Fiero plant. Meaning that the engine was likely built somewhere else, and everything was assembled as a complete unit, and all they had to do was plop it on the subframe, take the harness connector and plug it into the firewall.

As my daughter removed a lot of the wiring from the engine compartment, it seemed the most ridiculous was the harness that wraps along the front of the engine bay in that plastic shielding, which then goes to the A/C compressor. So I think it's safe to conclude that when they designed this, it was more ease of installation... and not necessarily what would be the most ideal wire routing. Has anyone (after rebuilding their engine and re-doing the engine compartment), re-routed some of the wiring, like for example, along the front firewall for things that otherwise don't need to be wrapped around the entire engine block?

When I did my 3500 swap i rewired the engine bay and removed about 3 feet from the harness. Instead of coming out of the cabin and going toward the front of the engine it went toward the back by the transmission. This engine had duel exhaust that came down from the manifolds so there was no crossover. I had only a couple that went back the other way to the fusible links but there was no wires coming across by the water pump to the fusible links. Looked much cleaner. My car car was a v6 but same idea.

Another think know better then GM Engineers... Worse another YT "show" wants more free help...

Duke wiring is Not just to make it easier to install.
For 1... Keeps most of wiring Far Away from the Exhaust. Wiring is Rated to handle engine heat otherwise.
2. The duke & others "loop" setup from ECM to C500 has the shortest wiring path for the FP AC Relays, many "ground" that some are Not Grounds, ECM Sensor wires, & way more. Example: The Distributor & TBI has wires to ECM & C500. While Alt has wires to C500 & Power "box" under that.
3. The "loop" has enough Slack to allow the engine to move & often even when have iffy engine/trans mounts & dogbone won't rip out the wiring.
4. if you need to pull the engine, For Fiero, you only need to discon C500, ECM, C203 & Maybe a few other plugs then drop the whole assembly out the bottom w/ the wiring. Ignoring rust frozen hardware, this can be done in Hours to get out then again to get in. And if you're careful you don't need wheel alignment if problems are in engine &or trans. & you don't mess w/ AC except to unbolt the compressor from mounts.
5. You can get to nearly all engine plugs/ends to easily test whatever even for OP sender to switch to 88 Plug to follow FSM directions to find most problems. + now you can get DC Amp Clamps & more tools to find a problem w/o cutting the wires etc. to test.

E2A--->
The AC compressor wires need a relay to work. So where are you going to mount that? There is no space near the battery for it or FP Relay. So if you put AC limit switches & Clutch wires, Clutch that pulls 7-10a even more, to go on firewall then have more wiring for the clutch not less when snaking around the battery to get to C500 that may need bigger "pins" to handle Clutch power.

IOW GM route all AC to C203 & ECM plugs so all go thru same path so Relay mounts in cooler area & no looking for other ECM wires going thru C500.
Because ECM has Final Control of AC because will turn the Compressor Off @ various conditions. 1 input line is you wanting AC & all limits are closed. 1 "output" actually turns On the Clutch Relay then that turn On the Clutch coil.

Go & look @ AC wiring in FSM Alldata etc that proves what I've said.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 11-19-2023).]

quote Originally posted by theogre: Another think know better then GM Engineers... Worse another YT "show" wants more free help... Duke wiring is Not just to make it easier to install. For 1... Keeps most of wiring Far Away from the Exhaust. Wiring is Rated to handle engine heat otherwise. 2. The duke & others "loop" setup from ECM to C500 has the shortest wiring path for the FP AC Relays, many "ground" that some are Not Grounds, ECM Sensor wires, & way more. Example: The Distributor & TBI has wires to ECM & C500. While Alt has wires to C500 & Power "box" under that. 3. The "loop" has enough Slack to allow the engine to move & often even when have iffy engine/trans mounts & dogbone won't rip out the wiring. 4. if you need to pull the engine, For Fiero, you only need to discon C500, ECM, C203 & Maybe a few other plugs then drop the whole assembly out the bottom w/ the wiring. Ignoring rust frozen hardware, this can be done in Hours to get out then again to get in. And if you're careful you don't need wheel alignment if problems are in engine &or trans. & you don't mess w/ AC except to unbolt the compressor from mounts. 5. You can get to nearly all engine plugs/ends to easily test whatever even for OP sender to switch to 88 Plug to follow FSM directions to find most problems. + now you can get DC Amp Clamps & more tools to find a problem w/o cutting the wires etc. to test. E2A---> The AC compressor wires need a relay to work. So where are you going to mount that? There is no space near the battery for it or FP Relay. So if you put AC limit switches & Clutch wires, Clutch that pulls 7-10a even more, to go on firewall then have more wiring for the clutch not less when snaking around the battery to get to C500 that may need bigger "pins" to handle Clutch power. IOW GM route all AC to C203 & ECM plugs so all go thru same path so Relay mounts in cooler area & no looking for other ECM wires going thru C500. Because ECM has Final Control of AC because will turn the Compressor Off @ various conditions. 1 input line is you wanting AC & all limits are closed. 1 "output" actually turns On the Clutch Relay then that turn On the Clutch coil. Go & look @ AC wiring in FSM Alldata etc that proves what I've said.

Hi Ogre, I think you're making a lot of assumptions here. Several of my wife's friends from UF ended up working for General Motors as mechanical, electrical, and space engineers. It's well-known that the routing of most wiring harnesses and the way they're designed has a lot more to do with ease of installation during the assembly and manufacturing process, rather than it does for any optimal path consideration. It doesn't take an electrical engineer to understand that wrapping an entire wiring harness around the engine, literally hugging it to the engine, and wrapping it down the front of the motor, is not the most ideal placement for most wiring. I'm certainly not asking what I can cut and remove.


"Worse another YT "show" wants more free help..."

You probably could have left that out... it was rather snide. I'm not asking for "free help." I can absolutely figure this out myself, it's not difficult, I'm asking for ideas to see what others have done. I want to clean up the engine bay.

Todd look over Fieroguru's ls4 thread to get some ideas as he does some incredible work on a fiero.

quote Originally posted by theogre: Another think know better then GM Engineers... Worse another YT "show" wants more free help...

Could you be any more condescending? I'm sure you could, if you tried.

Jeebus.

Todd, Just make sure the wiring - especially the battery cables - is routed away from hot exhaust, and moving parts (belts, pulleys, etc.)
I've done a couple of V6s. I wasn't too displeased with how the wiring was run, except that some of it had to be run before the accessory brackets and coolant pipes were installed.

[This message has been edited by Raydar (edited 11-19-2023).]

I never really questioned it.
I just assumed that they built the harness to accept any and all combinations of options for the engine.

quote Originally posted by Raydar: Could you be any more condescending? I'm sure you could, if you tried.

You're just another sucker for this racket...
Oh gee, kid want to rebuilt X car. Better is a girl wants it. Then parent(s) was Free info & more & push the channel/"show" to get viewer # hope to get viral or @ lest to get monetized etc. Maybe even local news coverage because "girls don't to this" @ outlet wants "feel good story" that week. Then get free stuff from vendors too. He's already getting Free Ads spamming General w/ posts for every "episode" on YT.

We've seen this happen here w/ big thread starter 10+ years ago. Some saw the "writing on the way" was going dead very soon as other projects/programs & making "statues" to sell ate more & more time But they Never told anyone. Many still didn't get a clue when she left for whatever university several years later.

I've seen this same thing happen many times in other places even before YT having most "Car Restore" projects that are abandoned in similar ways but YT & Internet have these making money, free parts & more. If they abandon the car, the free parts often go on CL Ebay etc.

Ogre, you got to chill out man.

You firmly believe the engineers know best. They don't always. I'm an engineer, I work in product development (electronics) for a extremely large company with products installed in almost every major building you have ever walked into since 1913. I know damn well that sometimes stuff is pushed out the door as a mother of necessity. Stop blasting everybody's ideas just cause they go against your philosophy of "that's not how the engineers did it." Especially when you're using the fiero as your guide for what the engineers intended. Every component of this car excluding the space frame and the panel construction absolutely reeks of rush job, cheap shortcuts and redundancy. Its just the nature of the beast. If we didn't have people who looks at something like that and went "Boy, i wonder if there's a better way to do this?" We'd still be riding horses without saddles.

You are attacking a member who simply wants to verify information before posting it to his daughters YouTube channel. Who gives damn if they are trying to grow the channel, the daughter seems to enjoy herself and its seemingly useful information. If the channel makes it 15 episodes and dies, what difference does it make? The daughter, a member of the youth you tend to criticize is attempting learning and trying to teach the tools and skills necessary to carry the torch your generation is leaving behind. As far as your diminutive statement of "wanting free information." its a forum guy, that's what they are for.

You aren't required to answer and support these things that your thrashing on. Even if your vast wealth of knowledge is appreciated and dont get me wrong, it is. It would almost be better that you don't answer if you are just going to tear everyone down while doing it.


Best thing you can do 82 T/A, if you are going to reroute, is keep focused on keeping wires as far from the heat as possible and as high up as possible, to make them easier to get to, and prevent hidden wires from causing faults later on. Maybe start with the OG harness and build a new one one wire at a time, routing each wire along there new path. Your gonna want to use heat resistant wire loom.

So a few years ago I had the whole engine bay empty. Took care of the old firewall insulation and did a lot of cosmetic touch ups to the rails, strut towers etc. When I went after the original wire loom and wire routing around engine the plastic and tape was such a degraded mess. Got every wire harness off the car, wiped/washed with Dawn dishsoap and warm dried afterwards. Then checked all the connectors for corrosion and ohm'd things out. Looked over the wire routing diagrams as well as some junked cars to ensure I put things back where & how they were done originally. I should have taken more photos prior.

I'm going for a restoration as best as I can do. If you're looking to alter things here's a couple things I'd suggest.

Pay attention to the surrounding areas for heat, vibration, movement of components in that area, suspension, engine, exhaust, etc. A poorly tuned engine can make the exhaust get very hot and melt the wire insulation. If you're planning on using the original wire harness check the assembly carefully. You don't want any knicks, cracks or breaks in the insulation.

Watch the routing, an idle engine doesn't move, under load, changed in acceleration/deceleration it definitely will.

Don't use the cheap/junk zip ties, either, they're susceptible to the same heat & harsh environment the wire loom is exposed to and won't last more than a couple a years. Use proper wire clamps, check out Auveco.

Good luck on your project,

BTW to all the neigh sayers maybe there needs to be a GOM section....

Just my two cents

quote Originally posted by theogre: You're just another sucker for this racket... Oh gee, kid want to rebuilt X car. Better is a girl wants it. Then parent(s) was Free info & more & push the channel/"show" to get viewer # hope to get viral or @ lest to get monetized etc. Maybe even local news coverage because "girls don't to this" @ outlet wants "feel good story" that week. Then get free stuff from vendors too. He's already getting Free Ads spamming General w/ posts for every "episode" on YT. We've seen this happen here w/ big thread starter 10+ years ago. Some saw the "writing on the way" was going dead very soon as other projects/programs & making "statues" to sell ate more & more time But they Never told anyone. Many still didn't get a clue when she left for whatever university several years later. I've seen this same thing happen many times in other places even before YT having most "Car Restore" projects that are abandoned in similar ways but YT & Internet have these making money, free parts & more. If they abandon the car, the free parts often go on CL Ebay etc.

Ogre, not really sure what the problem is. I don't quite understand what you're saying, but I'll just explain what my daughter is doing, since you seem concerned about it. My daughter wants to get into MIT. She's been wanting to go there since she was 11 for some reason, I don't know. I help her make these videos because she believes it will help her get into a good college. She also gets straight As. As a matter of fact, she just got her first "B" in about 6 years, and she's devastated about it (I tell her it's not really a big deal). She works really hard... does three sports a year, and has a lot of hobbies. To reward her for her good grades, I told her I would buy her a car, but that she had to restore it herself so she would be mechanically inclined. It was then she decided she wanted them recorded because she wanted to use them in an application to MIT. She's only 14.

What you are saying here, I don't even really know how to respond to some of it. My daughter is having fun doing this, and I'm spending father/daughter time with her... what is the problem? She's getting experience in public speaking, she's learning how to work on a car... and by the end of the Summer, will literally have totally restored a car entirely by herself. I don't do any of the work, except make sure she's doing it safely, and occasionally break some of the bolts loose because she lacks the strength to do it. As for me... if you think I'm doing this to make money, then I guess you don't know what I do for a living, or what my lifestyle is.

quote Originally posted by Dukesterpro: Best thing you can do 82 T/A, if you are going to reroute, is keep focused on keeping wires as far from the heat as possible and as high up as possible, to make them easier to get to, and prevent hidden wires from causing faults later on. Maybe start with the OG harness and build a new one one wire at a time, routing each wire along there new path. Your gonna want to use heat resistant wire loom.

Thanks Dukester... Rodney Dickman was selling some off-sized (screw-up) heat shielding wrap... I bought out his entire inventory as I plan to use those when I restore my own Fiero... but I figured I could use those when re-wiring her engine compartment. I just don't like the fact that the wiring harness (in her 4cyl car) wraps around the back of the engine and then wraps along to the side and down the front of the engine to get to the A/C compressor. I don't mind the part that goes along the back and under the intake... that makes sense... but for the A/C compressor, it's a poor design to have it go down the front of the motor behind that plastic shield and wrap around the bracket. To that point, it would make much more sense to have it go along the front firewall where the relays and the O2 sensor harness is already going. Plus, then I can remove that plastic shield that sits on the front of the motor above the timing bracket.

quote Originally posted by Stingray92: So a few years ago I had the whole engine bay empty. Took care of the old firewall insulation and did a lot of cosmetic touch ups to the rails, strut towers etc. When I went after the original wire loom and wire routing around engine the plastic and tape was such a degraded mess. Got every wire harness off the car, wiped/washed with Dawn dishsoap and warm dried afterwards. Then checked all the connectors for corrosion and ohm'd things out. Looked over the wire routing diagrams as well as some junked cars to ensure I put things back where & how they were done originally. I should have taken more photos prior. I'm going for a restoration as best as I can do. If you're looking to alter things here's a couple things I'd suggest. Pay attention to the surrounding areas for heat, vibration, movement of components in that area, suspension, engine, exhaust, etc. A poorly tuned engine can make the exhaust get very hot and melt the wire insulation. If you're planning on using the original wire harness check the assembly carefully. You don't want any knicks, cracks or breaks in the insulation. Watch the routing, an idle engine doesn't move, under load, changed in acceleration/deceleration it definitely will. Don't use the cheap/junk zip ties, either, they're susceptible to the same heat & harsh environment the wire loom is exposed to and won't last more than a couple a years. Use proper wire clamps, check out Auveco. Good luck on your project,

Thanks Stingray, this is exactly what I want to do. In my own Fiero (1987), I'm replacing the entire wiring harness with a new one (going with an aftermarket ECM / harness)... but the wiring doesn't seem so bad, but as you said, I plan to have her unwrap the entire harness and clean the entire thing with Dawn dish soap and then replace (solder) in new replacement connectors. As we were disconnecting things, I made a note of all the harness connectors that were either cracked or broken (most were in good shape), and I was able to order replacements on Rock Auto.

[This message has been edited by 82-T/A [At Work] (edited 11-21-2023).]

The way I see it and the way I do my swap harnesses is ...........near 40 years on, that section of the Fiero Wiring harness that goes along the block and back up into the cabin is still pristine and never has been an issue on any Fiero engine harness. it works, don't try to reengineer one of the few things that never gives an issue.

82 T/A

Stupid question, is your engine bay pass through connectors by the battery like an 86 or behind the engine like a 84. Seems like you are going to have to behind the engine to get to the center console anyways. I cant remember when the moved the bulkhead connectors over.

quote Originally posted by theogre: You're just another sucker for this racket...

Racket? YouTube? I couldn't care less what people do with YouTube. More power to them. No skin off my back, either way.

Sucker? Really?
I've listened to your effing "know-it-all" attitude for too many years now. Essentially, "If it isn't stock, it's worthless." It's long past tiring.
Aside from that, you know nothing about me, you cynical, condescending posterior orifice. GFYS.

[This message has been edited by Raydar (edited 11-22-2023).]

quote Originally posted by jelly2m8:The way I see it and the way I do my swap harnesses is ...........near 40 years on, that section of the Fiero Wiring harness that goes along the block and back up into the cabin is still pristine and never has been an issue on any Fiero engine harness. it works, don't try to reengineer one of the few things that never gives an issue.

Yeah, I guess I wasn't very clear. I had / have no intentions of changing the passage of the electrical harness through the firewall where it's going now. It's Ogre that said / inferred that I was doing that, but I am definitely not doing that. I just don't like that it snakes around the actual engine block like a vine, when instead only certain parts of it need to do that.

quote Originally posted by Dukesterpro: 82 T/A Stupid question, is your engine bay pass through connectors by the battery like an 86 or behind the engine like a 84. Seems like you are going to have to behind the engine to get to the center console anyways. I cant remember when the moved the bulkhead connectors over.

Yeah, everything comes in from the center, where the shifter cables connect through also. So I'm definitely not changing that... it's a great design. I'm also not planning on changing the fact that the harness comes in around the back of the engine (drivers side) and wraps under the intake manifold to the distributor, alternator, etc. None of that is going to change.

What I don't like though, is the fact that the positive cable feeds to the front of the engine, or that the HVAC connectors go down through the front of the engine in that plastic bracket. I feel like it's unnecessary, and that's what I'm looking to change. I just don't want anything going over or around the front of the motor. I have plenty of cable shielding, so I'll likely bridge the positive cable up and over behind the water pump, and then down through it's normal path, but behind the water pump, not over the center of the motor. I'll also re-route the A/C compressor connectors around the same location where the O2 sensor wire comes out, rather than going all the way around the engine, down the front of it, etc. That'll let me eliminate that entire plastic bracket, and clean up the front of the motor. My goal is to open everything up and clean up as much as I can.

My daughter has actually picked a light gray as a color for the motor too, with black accents (like the lifter plate and valve cover). I explained to her that you'll be able to see the engine more clearly and see if you have any leaks at any point.

[This message has been edited by 82-T/A [At Work] (edited 11-22-2023).]

first of all i enjoy her videos.im sure her dad is directing. im new to fieros but have had two third gen camaros.i like that her videos help me understand the odd fiero compared to other gms.since there seems to be several fiero iron duke experts in here im going to ask this.i just bought a 1987 2.5 auto fiero base coupe to swap a 1989 3.8 and auto that i have into.i found out noone is interested in helping me do that.i later bought a 1988 base fiero 2.5 auto from a junkyard probably closing down because of the owners bad health.i bought it because of the good condition body panels.it is almost complete.it seems to me this car was junked because of a fire in the battery area.is all the wiring in the engine bay coming through those connections on the passinger side of the engine bay?im wondering if a replacement engine bay harness might 'fix' this 'parts' car?