Where does the alternator brown wire go on no light trucks?

[urbex]

Trying to un-F the wiring hack jobs the previous owner did on my '86. Alternator died, presumably due to the battery hot wire he attached to the L terminal on the alternator. The brown wire he just grounded. I'm putting in a new CS144, and want to make sure I don't fry this one.

I have the volt meter on the dash, and can't find a battery/alternator light any where. Apparently some of these trucks just didn't get one?

I back traced the brown wire at the alternator to the firewall bulkhead connector, but can't figure out where it goes inside the cab. I'd prefer to have a light inside, even if I have to add one. Does it just end at the bulkhead connector on the no light trucks, and has nothing inside?

 

[Deewelch]

When I replaced my alternator (to correct the pulley diameter for the tach signal) I noticed the brown wire for the alternator had been cut and connected to a wire which went straight to the convenience center inside the cab. The original brown wire was in the engine compartment and the end of it was taped. It worked okay so I didn't pay much attention. I had bigger fish to fry.

Now I'm getting down to the small stuff. Since the warning buzzer wasn't working, I bought a new one. When I went to install it, I realized the buzzer was gone and that's where the alternator was wired to. The buzzer is a 7 terminal device and the alternator was connected to the bottom buzzer connector in the convenience center. I removed the wire and plugged in the buzzer. The buzzer worked great. However, when I fired things up, the voltmeter read low. I checked the battery voltage and it was about 12.5 volts. I removed the buzzer and plugged the wire from the alternator back in. The voltage went up to 13.7

The diagrams I've looked at haven't helped me on this. The diagrams show the brown wire going to an indicator light which I don't think I have (I have a volt meter).

 

[urbex]

I had my gauge cluster completely out several times today, and I didn't see any light for the alternator in there. I got the alternator in and wired up, using a 100ohm resistor to an ignition switched wire along with a remote wire on the sense line, and based on the voltage gauge in the dash, it worked great....until I reinstalled the cluster. Cluster in, I got 13 volts, and applying the brakes with the headlights on causes the voltage to plummet to below 9 volts. I gave up for the night, lol

 

[diesel4me]

The tan or brown wire is the one that sends 12 volts to the field coils and energizes them to start it charging,it comes from the ignition switch on most GM trucks,then goes to the fuse box,and exits the firewall there,and goes in the wiring harness to the alternator..

Trucks without an idiot light that have a voltmeter had either a shunt on the gauge, or a resistance wire in the wire, instead of using the idiot lamp bulb as the resistance..

Some resistance is needed in that circuit so the alternator wont just put out maximum amps and volts at all times..when the engine is running,both wires on the two prong plug on the alternator should have 12V present..
The thicker red wire "tells" the alternator voltage regulator the state of charge in the battery and it'll adjust the output as needed when more current is needed ,as the load increases..

It should not matter where the tan or brown wire gets its voltage from as long as it is only hot with the key in the "on" position and there is some type of resistance in the circuit..

Grounding the brown wire might have damaged the field coils in the alternator or the regulator..

 

[dyeager535]

Isn't that light one of the four under the speedometer or the fuel (or tach, large position) gauge?

I haven't dealt with that bulb in a long time, when they went to the CS130 style in these trucks, they used a separate indicator light where the clock used to be. Prior though, pretty sure every truck used a position under the gauge.

I can't view the wiring diagram for the cluster here, don't the pinouts for the I/P connector show that wire?

 

[urbex]

The 4 lights I under the speedo/large fuel gauge are 4WD, Choke, seat belt, and Brake. High beam over the speedo. I have had the cluster out and completely apart several times over the past few days, and can see no other indicator lights in there, nor does it look like something is missing in the open spot where the clock was on the older trucks. I also couldn't find continuity between the brown wire under hood and any wire position on the cluster connector in the dash, though it is good to the main firewall connector behind the fuse panel under hood. The wiring harness in this truck is a cluster-frick every which way, and plenty of hack jobs done to it, along with a poor installation of an Autopage alarm/remote start system at some point, so that's why I was trying to get locations of the wire, and how it's supposed to have been ran in the truck.

The ultimate plan is to rip out all the wiring in the truck, and put a new Painless style harness in, along with a new set of Autometer gauges, but that's not going to happen in the middle of summer here in Phoenix, lol. But for the time being, I just want to get this thing driveable. The alternator seems to work OK with with the way I wired it up - I added a junction block underhood off an ignition controlled relay, and ran a wire from the L terminal through a 100ohm, 10 watt power resistor, to that junction block. Then looped the S wire over to the battery post on the alternator. Now I just need to figure out what I screwed up when putting the gauge cluster back in that's causing voltage to plummet with the brakes on. Everything worked fine, with 14+ volts with the cluster out, but as soon as I reinstalled it, charging voltage dropped to below 13V, and goes down into the red anytime I hit the brakes, but comes back up with the brakes off.

Oh, and I tried to get that wiring diagram, but my work's firewall blocks that site too, lol. I'll check it when I get home.