Gen 1 light problem

[giterdunn]

I know yall are going to tell me to search, but I've read over 15 pages of topics and no answers. My gen 1 light stays on at medium brightness and gets brighter at hugh rpms and when the heater comes on. I read something about it being related to the heater fuse, but I can't find any blown fuses. The alternator is good I took it out and had it tested. All the voltmeter readings seem to be right:

key off:
batteries correct 12-13v, both alt positive wires read batt voltage, along with both red exciter wires, brown wires read 0

key on:

batt 1: 12.2v
batt 2: 13.2v
both batts: 25.3
alt wires same as before, brown exciter wire 1 is 12v and brown 2: 12.7

Engine running:

batt 1: 14.4v
batt 2: 15v
both batts: 29.3v
alt 1: 14.6v
alt 2: 14.8v
exciter 1 red: 12.3v
brown: 12.3v
exciter 2 red: 12.9v
brown: 12.8v

The other post confused me but from what I gathered those reading are correct, meaning there is nothing wrong with the charging system, so why is the light on?

 

[mktopside]

I had the same EXACT issue a few months ago, it was suspected that it was the diode in the alternator. I bought a new one from Autozone (it's not an isolated ground model but on Gen 1 it doesn't matter) installed it, problem solved.

 

[Warthog]

Your GEN2 reading should be 24v and not 12v on a stock system.

What type of truck is it?

Who tested the alternator? An alternator shop or one of the local parts houses?

 

[giterdunn]

Well I grounded it to the second batteries negative post so thats correct, when grounded to the case it reads 24v, The trucks an m1008, and an alternator shop tested it.

 

[giterdunn]

I had the same EXACT issue a few months ago, it was suspected that it was the diode in the alternator. I bought a new one from Autozone (it's not an isolated ground model but on Gen 1 it doesn't matter) installed it, problem solved.

I had the alt tested though. I guess it couldn't hurt to go ahead and get a 27si rebuild kit, I dont trust autozone alternators. Anybody have any other ideas? I'm really thinking it has something to do with the heater since it gets brighter when its on.

 

[Warthog]

The heater and the GEN1 excitor circuit share the same fuse. I have visually verified this.

With the heater on, it is drawing the majority of the current and starving the GEN1 excitor. My first guess is the voltage regulator.

The alternator kits are running ~$40 with new internals and bearings.

 

[giterdunn]

Seems like that would make the light dimmer instead of brighter though? I'm just gonna go ahead and order the rebuild kit, it'll need it sooner or later and I wanna keep this truck al long time.

 

[Wolf.Dose]

In addition to the above said: Did you check Gen 1 for propper ground contact? If ground is not propper, Gen 1 light might stay on even with propper working gen (just from experiance).Wolf

 

[mktopside]

Seems like that would make the light dimmer instead of brighter though? I'm just gonna go ahead and order the rebuild kit, it'll need it sooner or later and I wanna keep this truck al long time.

Just rebuild or replace it. I went through all of this a few months ago, it didn't make any sense to me. If you're not convinced....... swap the Gen's side to side and watch your problem move to Gen 2.

 

[giterdunn]

yeah good idea, I'm just gonna rebuild it though. I'm gonna rewire this thing one day, I just got new battery cables and post connectors, since the old ones were corroded pot metal, and the 12v cable was spliced in 4 places and 3 different sized of wire, lol. That ain't the half of it though, there a dozens of wires cut and tons of spliced. It was like that before the gen 1 light came on so I didn't think it could be the problem.

 

[mktopside]

yeah good idea, I'm just gonna rebuild it though. I'm gonna rewire this thing one day, I just got new battery cables and post connectors, since the old ones were corroded pot metal, and the 12v cable was spliced in 4 places and 3 different sized of wire, lol. That ain't the half of it though, there a dozens of wires cut and tons of spliced. It was like that before the gen 1 light came on so I didn't think it could be the problem.

Everytime I'm screwing with some electrical problem on mine I swear to myself that I'm going to redo the entire harness (Ive done this a few times when doing motor swaps on Hondas, it's not that hard, but takes a while). But, in the end I always find the problem just short of the point where I rip everything apart lol.

 

[sierrajcharlie]

I know if sounds dumb but replace the fuse just for the heck of it. Awhile back my oh9 was doing the same thing. I pulled the fuse, it wasn't blown and looked fine. I was shining it up a little with a knife when it fell apart in my hands. So I popped in a new fuse and it solved my issue. Maybe it was just a freak thing but fuses are cheap. Just my

 

[giterdunn]

I know if sounds dumb but replace the fuse just for the heck of it. Awhile back my oh9 was doing the same thing. I pulled the fuse, it wasn't blown and looked fine. I was shining it up a little with a knife when it fell apart in my hands. So I popped in a new fuse and it solved my issue. Maybe it was just a freak thing but fuses are cheap. Just my

Yeah I've seen that happen before too on tractors, I already checked em out and cleaned them up. If you guys think a cucv is a bitch with electrical problems, try an early 90's john deere, first couple years they had computers in tractors, it's a nightmare with all the dust and constant vibration.

 

[giterdunn]

Well guys I just rebuilt the alternator, it had a bad voltage regulator, but the light is still on. I'm almost certain the problem is in the wiring, but this truck has had an engine swap and half the wires are just hanging loose and the other half aren't hooked up to anything. It is the worst looking wiring harness I've ever seen. Can somebody please post a pic of their wiring harness? I need a pic of the 12v positive post on the firewall where the wires from the alternator are supposed to go.

 

[giterdunn]

Ok guys another update, when I unplug the exciter wires the light goes off, and the alt puts out 12.5v. But when I plug them back in, the light comes back on and the alt puts out 16v. I just replaced the voltage regulator.

 

[blackhueys]

look at the post I just made gen lights I had similar to what you have but all has been fine since I did what I did Look at my post.

 

[giterdunn]

Thats the same things I did but my light didn't go off.

 

[Warthog]

Ok guys another update, when I unplug the exciter wires the light goes off, and the alt puts out 12.5v. But when I plug them back in, the light comes back on and the alt puts out 16v. I just replaced the voltage regulator.

The correct voltage regulator will only put out 14.8v at tha max.

There is more wrong with your alternator or the wrong regulator was installed.

Did you follow the step by step procedure in the Tech Manual TM 9-2320-289-34 for testing and rebuilding the alternator?

Yes the light will go out when you unplus the 2wire plug. You are breaking the circuit for the excitor when you unplug it.

 

[giterdunn]

yeah I followed the instructions in the TM, the kit I ordered was the right kit (delco remy 27si). You think they sent me a bad voltage regulator.

 

[Warthog]

yeah I followed the instructions in the TM, the kit I ordered was the right kit (delco remy 27si). You think they sent me a bad voltage regulator.

Very possible.

I have had some bad parts in the kits. They are made overseas....