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I give, another wire harness question

8K views 54 replies 7 participants last post by  Tony_W 
#1 ·
My chevy truck, I purchased a new printed circuit from LMC becuase the old one was roasted and the dash lights were not correct. If I turned on the left turn signal the high beam would blink, stuff like that but more crazy stuff, trust me.

Well installed the new one and still the same thing, sucks.

All the outside lights have corporation, high beams work, headlights work, turn signals work, back up lights work and none of the outside lights are less dimmer than the other..

So, I'm stuck and have questions, I believe I maybe looking at a wiring harness but wonder if I could just rewire inside the cab?

But, I need something simple to install, something I can read and says use this color here and so on and so forth. Pictures would help too and don't know where to get that, only see wiring kits hsve this. Unfortunately they are not cheap BOO!

I seen a summit highway 22 harness for $400 bucks, I see painless harnesses for under $600 bucks but man I'm not sure what kind to get, hate to over pay for something that I only use 60% of?

If you guys have time for any advice on products that are easy to install or some other way I can get this done let me know.

I obviously want to pay as less as I can but know you can't always do that becuase you'll regret what you paid for.

Here it is, 1980 chevy c10 350/350 trans (plan to slide in a 700r4) 2wd, auto but I think it has a 82 or higher steering column.

I want my outside lights, inside lights, and plan to add air condition later. Will put in a radio system. So to me basic stuff. Guages I plan on are factory from LMC, will add a tach later as well, Just going to go old school on the truck, you know the look of 1970-1980 so nothing fancy on electric.

I hope i made sense and if not just ask away, I'll try to explain but I'm green on electric but not a fool. I'm green enough that I have never used a ohm meter.

Appreciate any feed back guys.
 
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#2 ·
Ask 10 people which kit is best and you'll get 20 answers!...... I like and use Painless, to me it's high quality for a decent price.
To be honest, I've never re-wired a truck.... only cars.

Some tricks ……….
Get a box of zip lock sandwich bags and a sharpie, a roll of masking tape (I use blue painters tape) 1 million zip ties. Buy some Packard type 56 terminals male and female, your kit has some but the brass ones didn’t crimp as well as the tinned ones I ordered. Get a good quality heavy duty crimper. If you want a complete wire diagram, draw it with the new harness laid out on the floor, I didn’t and ended up removing 3/4 s of it to draw mine.

As your remove parts and pieces put the screws in a zip lock and label the bag as to what they are for. Remove the instrument cluster, radio, AC controls, glove box, seats, drivers side sill plate and the wire protector underneath it.

Unscrew the fuse block bulkhead connector from under the hood, remove the all old wires completely before you start, I didn’t, thinking I might need to look at something etc...... big mistake and ended up doing it anyway. Try and remove the harness in one piece. Label all your connectors with tape and leave them connected to the wires, you might need some of the connectors later. Be very careful with the steering column connector, some kits don’t provide one and they are almost impossible to find a new one and you will have to reuse it, cut the connector off leaving about 3 inches of wire (very helpful later when you have to insert the new wires into it) When you get to that connector...... remove one wire and then insert the new one in it’s place. I removed them all and it was confusing when it came time to put the new ones in. As I went thru the different plugs it saved a lot of confusion.

MOUNT the fuse block FIRST! Be very careful with the template when cutting the firewall out to fit the new block, I had to do a little welding to fix mine.....lol. As per the instructions loosely route and bundle the wires that go to a certain area (that’s where the million ties come into play). Once you have all the wires loosely routed and you’re sure that’s all of them, starting at the fuse block, tuck, wire tie, and secure the wires as if that’s where they are going to stay forever, make any adjustments, then and only then cut the wires to their final length. DO NOT leave extra wire ”just in case you need work on it later” I left the extra wire and it ended up in a mess, looked like crud and I ended up re-terminating most of them.

If you have any under hood add-ons like elec fans, delay wipers, electronic speedometer, temp gauge, oil etc......... the bulkhead connector/fuse block has many unused pass thru slots (if you don’t use them, they need to be sealed with RTV from the engine compartment side). The Packard 56 terminals are the correct ones to add some extra wires from the cabin to the under hood area without drilling holes. I mounted the 70 amp maxi fuse (changed this out for a 70 resettable circuit breaker) on the radiator core support, just in front of the battery. The dome light wires in the kit, switch colors so be careful when you hook that circuit up (unless you removed that circuit in the beginning) I had an issue with the parking lights ground, ended up adding another ground wire. I purchased new metal taillight sockets, removed the wire that came with them, inserted the new painless wire into the socket and fiber disk, and soldered it to make the contact ....... no splice! Kind of did the same thing for the headlights, removed the pig tail and re-terminated it etc...... no splice! It’s a pain to remove the bulkhead connector, but it’s far easier to seal all the wires with RTV with it unplugged.

I run a new 8 gauge wire, in addition to the one supplied in the kit, from the 70 amp C/B to the bulkhead connector.

The whole project should take 2 weekends to complete.
 
#5 ·
some of your problems sound like bad grounds. the current flowing back thru some other component to find a ground.
^THIS!!!

Stop throwing money at the problem, which clearly isn't fixing it. Find the bad ground. Better yet, get a factory wiring diagram (BUY a factory book, don't cheap out with downloaded crap that may or may not be correct), study it, and figure out the problem. This info is all in the Chassis Service Manuals. You just need to read them.
 
#4 ·
Thanks EOD Guy, so the painless has good instructions your familiar with? When you say use your old wire as a guide then I have confidence on the engine bay and exterior lighting because it all works perfectly.

I don't have confidence in using the interior wires as a guide because things don't work right when I turn them on, again example is when I turn on my left turn signal all the back dash lights blink back and forth like a highway sign, BUT the exterior signal works?.

Timothale mentions grounds and I know what a ground can do if it fails, but I have not seen a ground inside the cab wiring? should there be?

There is 3 to 5 wires that are not hooked up inside of cab but neither is black( at least thats what I expect to find for a ground) and one for sure is the cigarette lighter, the other 3 or 4 I have no clue what they are for again they are not black.
 
#7 ·
I found a ground tucked away back by the high beam foot switch, comes out of the harness. I'll deal with that (be nice if thats,all it is) but should there be a ground going to the start switch on the steering column? The one that has the rod that moves when you turn the key.

Also would a bad turn signal switch be a cuase as well?

Just questions is,all.
 
#10 ·
I found a couple of basic wiring diagrams for an 80 C10.

If it were mine I'd start at the steering column connector and make sure the wires aren't jacked.

Then I'd look close at the instrument cluster connector and make sure the contacts aren't corroded. I have found this to be the culprit of many a wonky instrument cluster problem. I use an ordinary pencil eraser to polish the copper contacts.

As far as a new harness....... I've never seen a interior only kit. If you are keeping this truck, I'd go with a full harness anyway....... that's assuming you are going to replace the harness.

As far as downloading manuals ...... I've had extremely good luck doing just that. Now you have to buy the oem copies, not hayes etc...... I have many such CDs and sometimes that's the only affordable way to get manuals.
 

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#14 ·
Not sure I understand your lingo. I'll try lol if I understand it plugs into my bezel printed circuit one way, but I have considered flipping it to see if that is the problem, but I would need to sand a little on the slots so it could go in flipped. I hope thats what your asking, if I'm way off try explaining to me like I'm 9.

On a side note when I purchased the new printed circuit I also purchased all new metal connector prongs that snap into the circuit. There was only 8 of them and .75 cents each, something like that.
 
#13 ·
I found on my '75 GMC that most of the instrument panel problems you are describing are because the instrument panel ground is disconnected. With no ground, the instruments and lights find their own (unpredictable) path to ground and you get weird results.

It is the black wire up under the dash near the parking brake mechanism, and there is probably a post on top of the parking brake bracket where it is grounded. My ground had been removed for some reason, and when I put it back on it resolved nearly all my instrument panel and turn signal issues.

More grounds to check.
- Make sure there is a black ground wire to the radiator support on each side. The ground wire next to the battery is also connected to the battery negative.
- Make sure there is a ground strap from the rear, passenger side of the engine, running to the firewall behind it. It might be on one of the valve cover bolts, or it may be on the engine.
- Make sure there is ground strap from the engine to the frame. Usually near the fuel pump.
- Remove each of the park/tail lights to make sure the white wire is grounded well. It gets a lot of moisture in those areas and you may have to remove the screw, sand to bare metal, and then screw it back down.
- Look up under the rear bumper, right in the middle of the truck and you will find another white ground wire on the frame. Remove it, sand to bare metal, and then screw it back down.

I am also starting to use a product called DeOxit that they sell at Radio Shack and other places. It seems to be a better contact cleaner than the electronic contact cleaner they have at the auto parts stores.

Bruce
 
#15 ·
I'm missing some of those grounds, I only have one ground coming off the head light harness from the passenger side to the nose frame, that also runs back to the negative battery cable. The negative battery cable runs to the ALT. bracket. I will need to purchase a ground for the engine block and I will need to check the other grounds to mention.
 
#16 ·
What I was getting at...... If the connector wasn't indexed it could be reversed etc.......

Since yours is indexed....... You need to verify the wire color for each terminal on the connector. In your wiring diagram book, you should be able to find the connector and it will tell you which is the #1 pin/slot and what wire color it should be etc.......

It sounds to me like it's the connector/wires crossed...... or the terminals are shorting with the one next to it etc..... And as suggested above a bad ground.
 
#19 ·
Yep, we are thinking a like.

I had a buddy that bleeds chevy and he pointed out and few things and his opinion it looks like who ever put this steering column in spliced into the harness to match the steering column verses making the column work to the fuse box. So yea it appears the harness may have a wire or two wrong.
 
#17 ·
Once again - make sure the black instrument panel ground under the dash is grounded to the parking brake bracket or the body before you go through any big troubleshooting process.

That panel ground being disconnected will screw up multiple things, and fixing it will probably solve several of the problems you are having. I am speaking from direct experience with my GMC truck. Fix the ground before you start comparing wire colors for the large multi-wire connector on the instrument panel.

Bruce
 
#20 ·
I don't think there is a fuse box ground..

x2 on the grounds
make sure the body is tied to the motor and battery..

wtg finding the dash ground, but it could be loose at the dash connector too..
it shows 2 grounds on the connector, so there is another connection between them..
http://www.hotrodders.com/forum/attachment.php?attachmentid=334746&d=1481680521

x2 the pinout on the dash pod connector could be different on a gauge setup compared to a idiot light setup..
 
#21 ·
When I bought a replacement turn signal switch for my '75 I found that the plug on the new switch did not really match my truck. It was close, and you could make it fit together if you pushed hard, but all the colors did not match up. Maybe someone had the same issue with your truck in the past.

I had to cut the plug off my old turn signal switch and match the colors when I spliced it on to the new switch.

Bruce
 
#23 ·
Assuming you've verified the ground is good......GM colors haven't changed much in a long time. In the diagram I posted you can determine if the colors match the actual component ....ie

Frt R/H turn bulb should be Blue
Frt L/H turn bulb should be Lt Blue
Horn should be Black

etc...

Same goes for the instrument cluster, ie......

Blue and Lt Blue wires are tied from the steering column to the instrument cluster.
Grn (Temp sensor)is also from the column to the cluster
Lt green (Hi Beam) from the headlight switch to the cluster


You'll need to verify these circuits. You mentioned certain lights come on when they weren't supposed to... L/H turn and the hi beam blinks..... Lt Blu and Lt Grn may have been switched etc.....
 
#25 ·
I pulled the harnes, appears to be a 28 circuit, that what you guys count. Most wires seem accounted for except on the bezel plug, the diagram calls out 2 pink wires and I have 2 pink/black wires, still no book for me yet, looks like Monday for me.

The fuse box looks toasty but I'm no expert.
 

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#28 ·
It has some paint over it from last owner painting inside the cab.

In the diagram you guys gave me, there is pink wires but I have more coming and going, total 4 of then that hook together not separate. I also have a total of 5 grey or brown that come together. So I have more wires than the diagram.

I've been watching a kit on ebay a guy makes. He has 1247 positive likes on his harness's and zero negatives. He has a 12 circuit and a 25 circuit. Looks like most purchased the 25 circuits. Located out of Florida $123 bucks.
 
#29 ·
Start AT the problem and work backward.

Turn signal is making the high beam indicator light up I am not going to start at the tail lights. I am going to tear apart that steering column and yank out the switch and check it on a bench. I am going to check the connections at the key while I am in there. Then after that all checks out I am going to look at the pigtails them selfs to see if anything has decided to melt to anything else. If that checks out I am going to run my hand along the wiring and find whats cut, or is grounding out, or is missing grounds, etc.

It is a huge pain in the rear to find stuff like this. Most of the time it is a simple ground. Your not going to hurt anything by throwing in a few extra grounds that are rated the same as the grounds already there.

I have rewired over a dozen trucks. I have seen 2 instances where a bran new fuse box was wired to the old connections on the firewall through connection. If that is the case well don't do that. The through firewall blade connections fill full of corrosion and cause many issues.






You can bypass the column all together. For Testing ONLY. I don't want to be responsible for any fires if a hot at all times thing falls on the metal floor. I have never had that happen myself of course.:rolleyes:

You need a "help" key, a 3 way switch for the turn signal, a second 3 way switch for the wipers. Intermediate (wired with a resistor that has a off position), low, high(no park your testing)), a 2 way switch if you have a neutral safety switch, another 2 way for the 4 ways, and your good.
You run "hot at all times" power to the headlight switch light/flasher wiring and "key on power" to the accessories. This will avoid tearing the steering wheel apart. Cost is around $40. Go to a junk yard and get a female connection to plug the harness into then you will have all your wires needed in one neat easy to remove setup. You plug it right into the connection going to the steering column switches and then wire everything up.
 
#30 ·
Tony, some kits are better than others. It's the quality of the wire in the kit that matters, the connectors/terminals and gauge of wire. That's why I like Painless, plus they have the wire number and what it goes to, printed every 18-20 inches on each wire. If the ebay kit wire gauge is the same or better than oem it should be OK.

Before you buy the kit, get your diagram book and do some trouble shooting on that column. I use a jumper wire with a inline 7.5 amp fuse connected to the pos terminal on the battery and probe the column connector (the output side) ie... touch the probe to the Blue terminal and the R/F blinker light should come on and the dash indicator should come on etc........ if everything works as it should using the probe but crazy when the column is hooked back up then my bet it's the column.

Standard female crimp connectors fit a blade type fuse to make the jumper test probe.
 
#34 ·
I purchased the speedway 22 circuit kit #910-64022.

I've mounted the fuse box, ran wires to engine bay but not hooked up.

I have the turn signal switch corrected (new harness did not fit, so used it's clip and she is good now)

Next is the 2 piece ignition switch, first is the simple white one. I have the pink, brown and red that matches the speedway but I have the yellow one that's going to nuetral safety switch that I assume will be back up lights?

Not confident on this, I'm stuck.
 
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