Need some electrical info from the experts

[Richard Grant]

Some of you may have read about my exploits with the 4L80 trannie driving me crazy. First off I am not an electrical guy like my son is. After reworking the transmission and engine harness he wanted to know if resistance was calculated into the chassis for sensor and signal back to the ECM. I am wanting to attach new and better ground wires and even add a few. If anyone has input please dumb it down so this D.A. Mechanical engineer can understand. I'd like to impress him with knowledge. I play with molecules and he deals in electrons. Thanks a bunch, Richard .

 

[1994ch]

My understanding is these things love a good ground... so the better you can make the system the happier it is. This topic also reminded me of something the tranny guy told me when I got my trans rebuilt. Sometimes the mating surface between the trans and engine will get painted (say if its out for overhaul or something) that makes a bad ground connection for the transmission and can end up frying it (I think it was because the current would flow through the crankshaft and then through the torque converter)..... anyway he cautioned me to make sure that both surfaces were clean to make for a good ground connection.

 

[Richard Grant]

That is exactly what I thought too. Gabe ,my son, is an electronic switching and controls engineering guru and sometimes goes off on a tangent. Thanks for your input and validating what I reasoned.
I made up 6 or 7 #4 thnn grounds so now I will go ahead and attach after a little wire wheel work. Thanks again for your help, I'll show this to him because I like doing this to him. RICHARD

 

[JayTheCPA]

X-2 on more dedicated grounds. And bonus is to take them straight back to one of the negative battery terminals. As mentioned, electrons are creative in looking for the path of least resistance. Giving them a dedicated / preferred path back 'home' is a good way to go.

While not the best expert in terms of GM's thought process in the engineering design, from the perspective of somebody on the outside looking in, it does not appear that there was any consideration toward resistance and sensor inputs. So, feel free to start building grounding pathways back to a battery in parallel to the frame.

While on the topic of grounding, might consider adding one from the valve cover bolt above #8 (where several other grounds should attach) to the battery post. This location typically grounds the lift pump (LP), oil pressure switch (OPS), and powertrain control module (PCM (aka ECM or computer)). When this collection gets cruddy, resistance will increase the opportunity for simultaneously blowing the fuses on the LP and PCM. Learned this one from experience as it was a tow experience and learned how to fix it for good from old posts by Ferm and Missy.

 

[Richard Grant]

This is the reason I ask questions here, straight answers from people that I am not quite up to speed on. No more cocking my head sideways looking like a little speckled puppy trying to understand what I am supposed to do .
How would this work, I have a piece of buss bar that measures 5/16ths X 5"x30" that is silver coated copper. I will be relocating my battery from radiator support to inside of bed tool box complete with battery cage. This battery is for Heavy Equipment measuring 9"×10"×26". The amperage is somewhere in the 2 to 3K range. I will cut the buss bar to fit inside of a Hoffman box and use Johnny Balls to isolate the bar from ground contact. I then can attach as many Positive Home Runs as needed thus reducing the overall length and resistance of cables. Based on your reply I can do the same for grounding cables. I have everything except the 2 Hoffman boxes and they are pretty cheap.
You would not believe the HACK JOB done with the wiring and add on accessories on an otherwise pretty good looking truck. The previous owner suffered from a chemical dependency which explains a lot about the condition and price of the truck.
I will post a couple of pics. this evening of wires that I can't find in research. I do research everything throughly but come up short sometimes. The truck has a huge parasitic draw that I must find before I go much further. I mean battery draining in 6 hours draw!!! I know everyone has better things to do besides answering dumb questions for me.
A big THANK YOU to everyone here that has helped with this project. I'll always help anyone I can but am hesitant about jumping in due to only being here a short time. I'm a little funny that way.Once again THANK YOU, RICHARD.

 

[JayTheCPA]

Might not need to go that level with the battery, but everybody loves to see creativity in a good way

Toward the parasitic draw, if not already checked, try isolating the starter, alternator, and each of the relays. Might just get lucky and find the power leach that way.

 

[ak diesel driver]

Put an ammeter on the negative side of the battery between the cable and the battery. Then start pulling fuses and see which circuits have a draw on them.

 

[Richard Grant]

Hello gentlemen, I just came in and have a few pics that are head scratches. I need a shower and dinner, in that order before I do anything. My pain level is extremely high so it may be later before I get back to post. Thanks guys, Richard.

 

[Richard Grant]

Sorry gentlemen for not posting when I said I would. Now down to business, I'm attempting to post a few pics of the wiring both completed and still on the to do list. Under the hood is complete but under the truck is still a UFO, AKA UNFINISHED OBJECT. I haven't gotten to the battery cables so that is on tomorrow's agenda. Please give me all the feedback possible in case you see a better way of repairing the harnesses.
On the passenger side I have the harness pulled out over the fender. On the driver side there is an orange wire that has been dangling since I bought the truck. Underneath the body located on the passenger side frame rail is a small rectangular box with a black 2 or 3 wire connection. One wire goes to ground and the others connect to the box. I wasn't able to track the wire back at that time but you can see all the slack in the wire is zip tied up. Also you will notice there is an o2 downstream sensor that was not connected. This truck is always full of surprises The pics are from my tablet so am not sure how they will be.
Not sure what just happened but the post was sent while typing. Thanks to you all for your help. Richard.

 

[Richard Grant]

Sorry but the server timed out before the file transfered. Thanks, Richard.

 

[JayTheCPA]

On the driver side there is an orange wire . . .

Probably goes to the 7 pin trailer plug as the 12v supply for the trailer. IIRC, in the OE design, once connected properly, the lead in the 7 pin plug is hot all the time. If this is the trailer's hot lead and there is no intent to tow, consider leaving it alone. Naturally, connecting it later is always a possibility.

 

[Richard Grant]

That's a good idea, easier to trace with the transmission removed. Not sure I want to abandon in place anything electrical that is not OEM. I'VE just found way too much poor craftsmanship on this truck. Thanks for pointing me in that direction. Richard

 

[schiker]

I'm no expert but would like to comment.
I've never really thought about correcting for resistance to sensors or heard of anyone doing so. Except when adding extended harnesses (like for FSD/PMD).

It's very important to have good grounds and battery/alternator connections to keep batteries at a 12v plus a tad. sensors are usually 5v references and don't draw much current to cause much issue if a good connection. Note FSD above does have more current and electronic action to be sensitive.

I'll agree making sure grounds are good is the most important. Don't get too crazy adding doubling runs. Keep paths some what OE. Parallel connections good between parts/sections . I think the overall metal is good unless a bunch of rust or corrosion on thinner parts but straps between sections are good to beef up. Keep straps
Parallel so if OE strap fails you haven't created a weird path through something. The big draws are more important like starter, head lights, HVAC fans come to mind.

 

[schiker]

Adding bigger wires or relays for a load is different i.e. Lift pump or bigger charging wire/ starter wires etc than for sensors. IMO you can think slightly different for electricity vs electronics. One needs size both need good connections.

 

[Richard Grant]

Hey man, I think you just hit the nail on the head. I in no way know anything about electronics but am pretty good at electrical wiring and sizing. I do know commercial and industrial going all the way up to 2000 volts is what we referred to as medium voltage. D.C.VOLTAGE is a lot different as far as sizing goes compared to A.C. The D.C. section of my Ulgly's book is very easy to find due to it being overly used and abused. My plan for tomorrow is to install the new grounds just after I finish priming and painting the new pool furniture .
Thank you all for your guidance while I attempt to revive my Franken Truck. The truck is well worth the time and work that I am investing in it. Thank ya'll again, Richard.

 

[Will L.]

I am a sparky too. Ignore any normal rules when it comes to automotive wiring. Clean solid connections and how to chase an open/short are about the only things that transfer over. Rigs are like light fixtures- the manufacturer can do anything they want and get a stamp of approval somehow.

 

[schiker]

I just thought of something. The resistance of sensors seems to usually be in the ranges of hundreds of ohms up towards a thousand then dead short for full scale or zero. Such that a variation of wire length or some added resistance usually won't cause too much error.

It does not help a current type load issue.

One thing that seems to get me sometimes about automotive wiring is a lot of common nodes on the positive wires create weird paths since the ground is one big busbar.

 

[Richard Grant]

I am a sparky too. Ignore any normal rules when it comes to automotive wiring. Clean solid connections and how to chase an open/short are about the only things that transfer over. Rigs are like light fixtures- the manufacturer can do anything they want and get a stamp of approval somehow.

Yes sir on I.E. changes, I worked for Ford for 31 years. Process engineers and Industrial engineers did not necessarily get along very well. The process eng. was tasked with implementing changes no matter how dumb they were. I've seen some good ones.

 

[Richard Grant]

I've been away for a while due to health issues but today I've felt pretty good. I am continuing with plans to install the silver coated copper buss barr. I did change location to the storage box on the driver side. Will work perfectly. The box is out and buss bar cut to fit. I'll install the buss bar and isolators tomorow and reinstall the storage box to it's original location. The prestolite cable will be here tomorrow so I can make up the battery cables. I crudely fabed up a set of crimping dies for the lugs. They will be crimped and soldered for best connection possible.
The battery is 2300 CCA so it should do the job just fine. I got it lifted up on the tailgate but thats as far as I could get it today, so in the tool box tomorrow it goes, if I can pick it up again.
I am cleaning all ground straps and attach points with wire brush on angle grinder. I'm also installing new ground straps as a rodundesy as close to O.E.M. straps as possible so to maintain the engineered pathway. And I am still finding termanated and unlanded wires. I have all of my G.M. books out tracing circuts but cannot account for a couple of them. I'm sure there are more. Maybe more tomorrow. Richard.

 

[WarWagon]

I Don't get too crazy adding doubling runs. Keep paths some what OE. Parallel connections good between parts/sections . I think the overall metal is good unless a bunch of rust or corrosion on thinner parts but straps between sections are good to beef up. Keep straps
Parallel so if OE strap fails you haven't created a weird path through something. The big draws are more important like starter, head lights, HVAC fans come to mind.

"Don't get too crazy adding doubling runs."

Because, Why?

Noise.

Moving grounds or adding a thick cable to a bank of ground wires allows noise, especially the alternator AC wine, to transmit into them. Literally moving a add on "big 3" ground point 1" from a bunch of grounds instead of on the same bolt makes all the difference in the world. Specifically hearing the AC alternator whine through OnStar. Same thing happens to sensor and ECM grounds. So your ground cables need to be on a separate stud, bolt, or location than any OEM grounds.