Alt. signal wire

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,746
Reaction score
11,360
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
@Ricko1966 what brand of alternator did you go with?

I still just can't image how the ignition switch could cause this, but like you when I've got a problem, but no for sure source of the problem, I'll change out a couple parts just to be sure. Don't want all that wiring work to go to waste!
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
4,363
Reaction score
6,472
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
I haven't bought an alternator for anything in over a decade. Last time I needed one I drove to Kansas City,on the battery found a unit I liked and swapped it in the parking lot. I've been able to steal almost all my alternators off one of my parts cars or spare engines. Usually all that goes bad is the diode trio,the regulator the brushes or the bearings. Which I'll take one or two of NY junk alternators and make a good one. I've better luck with that than remans.remains. I've had great luck with Bosch remans we installed tons of those at the shop and don't remember any bad units or comebacks,there probably were some but so few it wasn't a problem.
 

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
@Ricko1966,
Yeah, thanks for your response. And yes, you are right, spare parts is the way to go. The new or newly remans. are getting just to expensive. But unlike yourself I didn't have a bunch of spare cars to rob from so instead I had a couple of bags in a box of all kinds of spare internal parts to choose from. I would take a alternator apart and buy a new diode trio and other parts inside, and put the old one in the bag, rectifier bridge, etc.. Also, I'd have resisters, all the screws, and a handful of capacitors to choose from the next time I rebuilt mine again. Of course it's not like my alternators were going out all the time, it might be many years. But most of the failures was from a voltage regulator going out. As time went on they got cheaper and cheaper made. Now, there is no Delco Remy made in America alternator parts. They are all made in China.
And let me tell you something, what do you think China did before they got all our manufacturing? They were and still are in the counterfeiting business, big time, everything you can name. Auto Zone was under Federal investigation for the fact two of their huge warehouses were busted in China full of parts boxes that looked identical to Ford, GM, and Chrysler parts. This was back in the early '90's and unless you put a real parts box up to theirs you couldn't tell the difference, and the parts inside looked perfect. But what they'd do is rebuild the part just right but in a couple of internal components they made from pure junk. Two days after you put the thing on your car it would fail! I know because I got one of those water pumps and two days later it failed and I had to go get another one. The first day I changed it out it was 15 degrees, the second time I changed it out it was 12 degrees.
I don't buy anything from Auto Zone anymore especially after I installed the second pump I read where Auto Zone was under investigation for selling Chinese counterfeit parts. And that was the second time the had been under investigation.
 

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
Today I fixed a wire in the engine compartment that since I did it, it's been bothering me. I kept looking at the schematic and comparing what I found when I was undoing tape from the factory wiring at the junction block and alternator wiring and those factory splices. I was preparing to route the wiring for my new amp. gauge wires.
In the pic below this is what I found instead of the #16 wire which was supposed to be a "fusible link". This is factory, now! There has been tape on this since I bought the truck. Well, I decided to take a look and I was shocked to find this. I've been driving the truck since 1981 like this and I never had a problem.
You must be registered for see images attach


This is how the original wiring was.
You must be registered for see images attach
 
Last edited:

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
And this is what I did to it.
You must be registered for see images attach


At this point I soldered it to the alt. wire part of the amp. gauge install. But i later changed that as I studied the schematic further. If you go to April 28 of this thread you'll see the small wired "fusible link". It's been changed, again. I put a piece of #12 red wire back in place of that #16 when the other night after i restarted the truck I was checking the wiring in the engine compartment and noticed that little wire's insulation had wrinkled as it would do if it got real hot from carrying to much juice. So I put it back the way it was.
You must be registered for see images attach
 
Last edited:

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
I've already gone over all this. So, I won't repeat myself. So, today after cutting out that #16 wire and putting back in it's place the #12, since I drove the truck like that for over 25 years and never had a problem. So I guess there never was a problem with there not being a #16 wire, as shown in the schematic. Feeling better with removing that little wire, that looked like it had gotten hot, I went ahead and installed my new Autometer Sport-Comp Amp gauge that all this was leading up to anyway, until that is, the little alt.wire caught on fire. But I guess that's why God let that happen because He knew there was a problem with that old alternator part, the stator, and it would have made me really mad if I put that new gauge in and then possibly burned it up. The first amp gauge I fried right off and hooked one of the wires to ground. That killed that one. Second one I fried accidentally when I didn't unhook the battery and was taking the wires off the back of the first amp gauge and putting the new second one in, touched one of the wires to the screw on the back that already had a wire hooked to it. That killed that one. It didn't work after that so I know I fried it. At least the second one didn't cost anythingm, I already had it. But this one, the third one (everything runs in three's) I wanted to make dang sure everything was like it should be before I hooked the battery up and turned the headlights on to check it. No more wiring problems...Please!!
If everything is okay I'll take a pic of it working. Also to, I was thinking that since I don't have anything drawing off the system other than stock lights, and a stock radio, stock heater fan, that 60 amp + -- may be to high. I might have to get the 30 amp + -- to even see the needle move.
Or what does anyone think?? 60 amp amp gauge to high? 30 amp might be better? I'll see if I can see the needle move then I'll decide. The other gauges may have been fine and the needle was moving so little I couldn't even tell. Possibility??
 
Last edited:

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,746
Reaction score
11,360
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Or what does anyone think?? 60 amp amp gauge to high? 30 amp might be better? I'll see if I can see the needle move then I'll decide. The other gauges may have been fine and the needle was moving so little I couldn't even tell. Possibility??
Good question, I'm not sure anyone has the answer but I'll speculate a little. The 60 amp is fine. I'll even say it's better than the 30, why you might ask. What is the rating of the alternator you have? I'm not sure we ever discussed this but for the sake of discussion if it's a 78 amp unit, and lets say the battery is really ran down, you fire the truck up and take off. The alternator is pumping out every thing it can as you roll down the road, your producing more than twice what the 30 amp gauge can read, can't that damage the gauge? Pretty sure it can. So you might not get to see the fine needle movement as well on a 60 amp gauge, but at least it can better handle the full production amperage of the alternator.
 

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
@SirRobyn0 ,
Yeah, sorry 'bout that and I'm sure it is important to understand what I need. It originally was a 55 amp alternator, and that is with all I have in the truck now which is no more than when I had the 55 in there. Well, this new alternator is a 68 amp. So I would guess the battery would have to be down a lot for it to peg out the 60 amp. gauge. and still have that 8 amps. to go. What I would like to see is some kind of a graph that shows how low the battery would have to be compared to what the alternator is putting out. I'm sure I don't understand it now. Like my battery is a 650 cold cranking amps. Die Hard. I don't know how much it is in static amps. I suppose I could put an volt/ohm meter on it and what, put it on amps and.....I'm lost already. I'll have to read up on testing the alternator and maybe it will tell me how to test the amperage output of the alternator. Maybe that will give me somekind of lead on it.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,746
Reaction score
11,360
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Kind of fun to speculate on that stuff. I don't think that 8 amps i anything to worry about. I don't think you can measure amps in static amps. You can load test a battery to see how many amps it can "give" at whatever volt you crank the tester to. And of course batteries are rated in CCA and / or CA.

Realistically though if you have a carbon pile load tester, you could hook it up to the battery, put the amp clamp on the charge wire from the alternator, fire the truck up and put a high load on it. Maybe drag the system down to 10 volts and rev the engine to 1,500 RPM or more and see how many amps that alternator actually makes.

Still I don't think it matters. I doubt you hurt that 60 amp gauge.
 

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
@SirRobyn0,
That was what I couldn't remember last night, "CA", cranking amps! I knew there was another designation but I couldn't recall what it was.
And that is correct, a "carbon pile" is what the factory maintenance manual says to use to make the alternator put out all it can put out. Okay, that would be interesting but what else can you do with it? I don't know. When I first got that manual and was just reading different things on the truck I came across that and I had no idea what it was talking about, and heck man I'm old enough for something like that to have been used, I think? Like, I guess I could look one up on line but what did they use such a thing for back in the day? I don't know that either, ha, ha.
Well, I did what I said I was going to do today and that is to switch the wires around on the Amp. gauge and put them back to the way the Autometer directions indicates they should be hooked up initially with the starter wire on "S" for starter, and "I" for ignition to really take a close look at and see if I could actually see if the needle moved in the wrong direction. And it did...again. So I switched them back around. I'm calling Autometer tomorrow and get the low down on why do the wires need to be switched. The gauge should work like it's indicated. I tried to think about that, taking the electrical system configuration into consideration, the alternator direction of rotation, field charge, etc. and I couldn't think of any logical reason why the wires should need to be switched.
You guys with stock gauges, and if you have a amp. gauge, I had one, in your truck are hooked up exactly like the Autometer instructions say to hook the wires up, with one going to the starter, down there on the positive post where the battery cable goes, and the other one going to the junction block on the firewall where the alternator wire is. Along the firewall there should be two of those push together fuse holders with each one having a 4 amp. fuse in it. That's how mine was and it had never been tampered with.
Oh well, so I cranked the truck up and drove it to Walmart for the first time, in a month!

In the upper right hand corner of this pic you can just make out the back end of one of those push together fuse holders and it's black wire goes through that tape and is part of the factory connection at the junction block with one of the alternator #10 wires. Then below that in front of the big conduit is another #12 red wire with another black wire connected together going to my battery cable, going down to the starter.
This is more or less how yours should look if you have a amp. gauge in your truck. Now, I made my own junction block because I took out all that wire that runs across the top of the block and underneath the exhaust manifold and then down to the starter. That I cut out and removed over five feet of excess wire going to the starter. From my junction block I just dropped down the firewall to the starter. That's how it should have been done at the factory. I don't know why they did it the way they did. I didn't remove any wiring that wasn't already there. "S" is the #12 green wire coming from the neutral safety switch, and "R" is the coil wire going to the starter. The red wires are the alternator wires, and black stock amp. gauge wires, just like stock. Of course these wires are before I put my amp. gauge wiring in, and it's only a slight change. And I removed the stock amp. gauge wires.
You must be registered for see images attach
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,746
Reaction score
11,360
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
That's good info. I may add an amp gauge one day. I'd like to anyway, will I ever get to it? Hard to say.

As for the carbon pile load tester we have one at the shop and it is our go to testing unit for alternators, batteries and starters. So what can you do with it.

A standard battery test would be to hook the tester up and with the engine off apply a load to the battery to bring it down to 10 volts. and take note of number of amps, then take it down to 9 volts and take note of the amps again. Ideally the battery should be able to produce 1/2 it's CCA's at 9 volts, at minimum it should be able to do it at 10 volts. Less than 1/2 the CCA at 10 volts is a fail.

For the alternator it hook up the load tester. Fire the engine and rev it up to 1,500 - 2,000 RPM, and apply a load. You should be able to get to the alternators rated amperage without dropping the system voltage to much. There is kind of a judgement call in there. The nicer older load testers like the one at the shop you can hit a button on it and watch the diode pattern as well.

Obviously you can hook it up and see how many amps your starter draws and how much it drops the battery voltage.

That's about all you can do with a load tester. While it's only got a few uses it's really good at what it does. Some of the smaller hand held load testers just have an on off switch for the load and can only pull about 100 amps. Those tester aren't really that great as you can't vary the amount of load. So look for one with a variable knob, preferably something that can pull at minimum a 300 amp load 500 or more is preferred.
 

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
@SirRobyn0,

Wow! That's amazing! I can see where it would be a good tool around a shop though. I don't think I would get much use out of it since I may only use it once or twice.
But you know when I worked for the airlines I bought tools that I knew I would only use once or twice a year or less, only when we were doing a C6 inspection when we would pull the wings off the plane and do dye checks of the wing root plates and bolts and such. Then to get in there you needed special wrenches and whatnot. We bought Mac tools for all that as we had a Mac guy come around maybe once a month or so, and I've got some 15/8" by 17/8" open end wrenches and one other, I'd have to go look at it, just for those big nuts in the wing root, and tail to. That doesn't sound big but there are four and the only way in there is with a hand tool and a lot of elbow grease. And you know how it goes, if you were borrowing tools, which we all frowned upon, if the guy who had the wrench had gone home you were screwed. And the airline didn't provide hand tools. You had to have your own. So we all bought our own.
Yeah, the carbon pile the maint. book refers to is the kind like you said was a better one, with the knob you turn up and down. Woow, 500 amps.! Holy smoke! That's welding machine amperage.
 

Raider L

Full Access Member
Joined
Sep 1, 2020
Posts
1,892
Reaction score
998
Location
Shreveport, LA
First Name
William
Truck Year
1974
Truck Model
C10
Engine Size
355
@SirRobyn0,

When you do your amp. gauge just remember the only wires you hook up to it is the red alternator wire and the battery cable, actually. The way these trucks with amp. gauges are is one wire goes over to the junction block where the alternator wire is, and the other wire goes down to the lug where the battery cable is. That's all there is to it. Just make sure you use #10 wire.
Now, what you guys with gauges will find is one little bitty #20 gauge wire for the one going to the junction block with a inline fuse holder, and it will be made into the terminal end of the wire from the alternator. And the other amp. gauge wire is a #12 wire going down to the battery cable at the starter. Both those wires come out of the firewall wire block and come from the gang plug at the back of the printed circuit. But it will have a fusible link wire on it at the starter, and probably one of those plastic things the smaller wire passes through and the end coming out of the the plastic thing is probably a #20 gauge wire to the battery cable lug. Back up near the main harness may be another fuse holder, both of those are a push together type with a 4 amp. fuse in each.
I wondered about the size of those wires when the Autometer instructions said to use #10 on it's gauge.
But that was the giveaway and it is because GM amp. gauges are built to only measure a small percentage of the current and the insides of the gauge are made for that. Whereas the Autometer gauge is made to handle all the current.
And here lately it still makes me think about all the other amp. gauges I tried thinking none of them worked when the needle never moved. Well, neither does this new one I've put in except for the two times I put the test to it after switching wires to opposite posts, and that was the only time I saw the needle move just a little, and I had to make sure I was starring right at it to catch it when it did move. Otherwise I would have missed it both times and probably would have thought that gauge didn't work either. I just really never understood how fast the alternator recharges the battery from the little tiny bit of juice it replaces after crank up. That is, if your truck is out of tune and takes forever to start. Mine doesn't take any time at all to start.
 
Last edited:

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,746
Reaction score
11,360
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
@Raider L I had a larger hand held carbon pile load tester in the barn on the farm. The problem with it was after years of being used only rarely it eventually quite working. I always think a guy can get an idea of alternator and battery health just by turning on the lights and the blower and observing system voltage and / or amperage. It's not the same as a load tester but it works.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
6,746
Reaction score
11,360
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
@SirRobyn0,

When you do your amp. guage just remember the only wires you hook up to it is the red alternator wire and the battery cable, actually. The way these trucks with amp. gauges are is one wire goes over to the junction block where the alternator wire is, and the other wire goes down to the lug where the battery cable is. That's all there is to it. Just make sure you use #10 wire.
Now, what you guys with gauges will find is one little bitty #20 gauge wire for the one going to the junction block with a inline fuse holder, and it will be made into the terminal end of the wire from the alternator. And the other amp. gauge wire is a #12 wire going down to the battery cable at the starter. Both those wires come out of the firewall wire block and come from the gang plug at the back of the printed circuit. But it will have a fusible link wire on it at the starter, and probably one of those plastic things the smaller wire passes through and the end coming out of the the plastic thing is probably a #20 gauge wire to the battery cable lug. Back up near the main harness may be another fuse holder, both of those are a push together type with a 4 amp. fuse in each.
I wondered about the size of those wires when the Autometer instructions said to use #10 on it's gauge.
But that was the giveaway and it is because GM amp. gauges are built to only measure a small percentage of the current and the insides of the gauge are made for that. Whereas the Autometer gauge is made to handle all the current.
And here lately it still makes me think about all the other amp. gauges I tried thinking none of them worked when the needle never moved. Well, neither does this new one I've put in except for the two times I put the test to it after switching wires to opposite posts, and that was the only time I saw the needle move just a little, and I had to make sure I was starring right at it to catch it when it did move. Otherwise I would have missed it both times and probably would have thought that gauge didn't work either. I just really never understood how fast the alternator recharges the battery from the little tiny bit of juice it replaces after crank up. That is, if your truck is out of tune and takes forever to start. Mine doesn't take any time at all to start.
Your last line. "If your truck takes forever to start". I'm like you, one pump, turn the key and she's running. I can put up with a cold blooded rig if it's a rarely used rig, but not on my square, I drive it year round in all kinds of weather, it's got to run right warm or cold.
 

Latest posts

Forum statistics

Threads
42,569
Posts
918,526
Members
34,110
Latest member
mundo
Top