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Discussion Starter · #1 ·
Well, guess it's my turn to ask a question and see if I can get some help.

I recently tore down my truck, pulled the engine and I started to tidy up the wiring when I noticed that the alternator was setup as a 1 wire. I peeled back the loom and notice the previous owner cut the pigtail off that makes this a 3 wire alternator setup. This is on an 85 c10 silverado all electric. The red battery wire that goes to be back of the alternator is fine and is all there, one wire is the brown wire, but the other wire which I think is the white wire is nowhere to be found. I took some pictures and see if anyone can help me out. I would like to use the 3 wire setup if I can locate the wires. the last pic show a cut wire I found that is pink with a black or brown stripe. Don't know if that is for the alternator wire??

Also there is a second electrical question: I also found the pigtail for the oil pressure switch (I think??) and it had two cut wires. (See second pic). One an aqua green and the other a peach with white line wire. You can see it in the pic as well. Any help on getting this fixed would be appreciated.
 

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Not sure what you have that your calling the O.P. leads. Alternator #1 is the exciter lead #2 and the main lead (big Red) go back and are tied together. Do a search on Yahoo and look at images. Or buy the manual for your truck they cost about $25.00 at parts store and are for that truck and come with wiring dia.
Hope this helps.
 

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Discussion Starter · #4 ·
Not sure what you have that your calling the O.P. leads. Alternator #1 is the exciter lead #2 and the main lead (big Red) go back and are tied together. Do a search on Yahoo and look at images. Or buy the manual for your truck they cost about $25.00 at parts store and are for that truck and come with wiring dia.
Hope this helps.

The image with the plugs from what I can tell is for the oil pressure, I grabbed a 2 prong oil pressure switch (factory) from the scrap bin and it matches up.

I do have the batter Big Red lead, that's not the issue. I know if you have the 3 wire setup it had the Alt. #1 and Alt. #2 pigtail. I just cannot verify where the white wire, if in fact it is suppose to be white, is. the other wire (brown) is there and looks like i just need to add the pigtail. I even searched underneath the dash and on the firewall plug to see if something was cut off. I could not find anything.
 

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Discussion Starter · #5 ·
Wires for o\p switch probably for electric choke
Thanks Blue, I am thinking that, but I guess i will have to get diagrams or get someone who know more about this than I do.

The truck runs good, it's just that I get annoyed when I see cut wire, and there is no real explanation for it that I can see right off the bat. I guess I am my own worse enemy when it comes to cleaning stuff up on these old cars.
 

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ok I checked a wiring diagram for you.The round 3 wire connectop goes to a o\p switch.Lite blue wire to choke heaterat carb,dark blue wire to I\p choke light,pink\white wire to fuse 12.Alternator-brown wire to terminal 1 on alternator,it comes from either ignition switch or I\p depending on whether you have a guage or lite,terminal 2 goes to the starter bat terminal with a fuse link but most guys just loop it to output terminal .Hope this helps you.
 

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Most of those trucks that is 1\2 ton were 305's with 4bbl and esc.Most changed them with 350's and did away with some of the emission stuff,hence cut wires,open vacumn lines,etc
 

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Discussion Starter · #9 ·
Alternator Pigtail

One additional question.

Since I have the brown wire there witch I think goes to Terminal #2, Can I get an aftermarket pigtail and connect it like a 3 wire setup and leave the white wire dead? Will there be any issues, other than not having an "idiot light" indicator charge light to the instrument panel.

I do have an 84 c10 out in the ranch that is all original, which I will check the wiring on this weekend, but just wanted to ask and verify on this. Looks like 84/85 was the year they did some emission changes, hopefully the wiring is similar if not the same.
 

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Discussion Starter · #10 ·
Wiring Diagram From Autozone website

Just in case anyone ever needs this. I found this Autozone website and it has the whole 80-87 wiring diagram for free. I don't know how accurate it is or where they got it, but it's worth a shot.

I can already see some of the colors don't match up to what my truck currently has, but maybe I am not looking at it right ???

I don't claim to be an automotive electrical know it all. :)

Here is the link:
http://www.autozone.com/autozone/re...epairGuideContent.jsp?pageId=0900c1528004c636

To download and attach it to this site I exceed the limit. otherwise I would have added the pics and the descriptions.
 

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First brown goes to terminal 1.On terminal 2 this is the voltage sensing terminal so putting it there may not work right cause idiot light adds resistance to the circuit.Just loop terminal 2 to output and you should be ok
 

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Discussion Starter · #12 ·
Brown Wire

Blue,

I think your right. I miss-typed what I said about the brown wire. I found some alternator sites that states the Brown goes to the indicator light. The second wire (smaller gauge red)is a 12V source that ties into the larger battery wire somewhere down the line after the fuseable link. Or from what I read and what you just told me I can jump it to the back of the alternator where the larger gauge red wire connects. Now I just need to find the rest of that darn brown wire, I cannot locate the end that goes thru the firewall and into cab.

You got any ideas on the second question I had about the Oil pressure sensor plug and the two cut wires??

I know, now I am just being annoying. Sorry.
 

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ok I checked a wiring diagram for you.The round 3 wire connectop goes to a o\p switch.Lite blue wire to choke heater at carb,dark blue wire to I\p choke light,pink\white wire to fuse 12.Some had the switch in a brass tee next to distributor and some went in the block above the oil filter.If I remember right all wiring goes thru bulkhead by brake booster with exception of ESC,A\C-Blower,and dual tank if equipped.Really stretching memory now ,old guy needs to take a nap
 

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Discussion Starter · #14 ·
ok I checked a wiring diagram for you.The round 3 wire connectop goes to a o\p switch.Lite blue wire to choke heater at carb,dark blue wire to I\p choke light,pink\white wire to fuse 12.Some had the switch in a brass tee next to distributor and some went in the block above the oil filter.If I remember right all wiring goes thru bulkhead by brake booster with exception of ESC,A\C-Blower,and dual tank if equipped.Really stretching memory now ,old guy needs to take a nap

Blue,
Excuse my ignorance, but what is I\P stand for. I know O\P is for Oil pressure switch, but not familiar with I\P. Again, excuse my ignorance on this.
 

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Discussion Starter · #16 · (Edited)
Thank you Blue Goose

Blue, If your interested just wanted to give you an update since you helped me out quite a bit.

1. I think I got the alternator issue figured out. Yes I will follow your instructions and reconnect the brown wire, which i traced to the inside of the cab and everything is good, no other cuts on the brown wire that I saw other than at the alternator pigtail. So I will be going back to a 3 wire alternator setup and getting a new alternator.

2. The pink/with black stripe wire I mentions at the first of my post seems to be for an air diverter solenoid/ carburator air purge solenoid/ carburator air fuel solenoid?? I am still a bit lost on this one. Help ??

3. The oil pressure plug and the colors you mentioned before were correct. After I got some thinner and cleaned up the wire and removed the gunk, yes there is one dark blue wire that is currently all connected up into the inside of the cab running to the instrument panel. This one is not cut at all.

The pink/ with white stripe wire that was also cut seems to have been cut to be used as power to the edelbrock carburator the previous owner installed. So I think I can reconnect this wire back and re-figure the electric choke, by doing one of these options: A) See if the pink/ with black stripe wire that i mentioned before has juice with the key to be used for the carb. electric choke. B) Tee off the pink/ with white stripe wire since it pretty much is connected that way already. C) Follow the recommended process on Edelbrock's website to connect an electric choke on this aftermarket carb.

The third wire that I thought was a blue/green color is in fact a light blue color like you mentioned. So I will need to figure out if it really needs to be connected to the choke heater at carb. like you mentioned before to make the oil pressure switch and gauge work. I am still lost on this process, so If you can help me out with a diagram or visual pic that would help me out.

If you can't tell yet, I want to at least give it the old college try and see if I can get the factory oil pressure gauge to work properly. I will buy new oil pressure switch and gauge if needed. All the other gauges work fine, even the alternator volt gauge worked good. It currently has an aftermarket oil pressure gauge installed but like I said, i would like the factory to work also.

Blue, thanks for your continued help on this, as you can tell by now, I am a novice when I come to the electrical system on these things.
 

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Pink with black should go to idle solenoid.3 wire connector to 2 blade o\p switch is only used for choke heater.This switch is used so no power goes to heater unless engine is running to keep from burning out heater element.I would suggest not hooking to switched ignition power.The tan wire with black boot looking connector goes to single terminal o\p sender for the guage.Will try to get you a full diagram
 

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Discussion Starter · #19 ·
Blue,
I will wait to see if you can get me that diagram. I think having a visual will help alot.

Again, thanks for all your help. you da man.:)bowtier
 
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