M1008 CUCV Gen 2 Light

[wigwag11]

Guys I'm new here so please have mercy on me. However my problem is that my Gen 2 light comes on dim (like half lit) when I turn on the ignition and then stays the same as the truck is running. I have been through all the posts on here and, all the TM,s. The truck is stock with nothing other than factory wiring, it has 2 brand new interstate 31 series batteries with the front having 14.3v and across both 28.4. After cranking the voltage at the batteries and at the volt meter drops to 27 then quickly comes back up to 28.8v and eventually 29v. If i cut on the lights and heater blower it drops to 28.3v while running and when they are shutoff again it climbs back up to 29v. The light never brightens or dims just stays constantly half lit no matter what. I am very mechanically inclined and have been over every wire with a volt meter. Oh forgot to mention that I'm getting 14 on Gen 1 exciter wire not running and when running 14.3. On Gen2 I'm getting 28.4 at the exciter wire just like the batteries and once it is running i get 29 at the charging wire coming off Gen 2. Im really lost to why the Gen 2 light comes on dim and why it stays on. if anyone can help it would be great thanks.


85 M1008 CUCV Stock

 

[Barrman]

You have entered the voodoo section of CUCV wiring. Do you have the exactly correct number bulb in the Gen 2 light socket? Have you taken the 6 pin ground terminal off the parking brake bracket, cleaned it and cleaned all the ground wires connecting to it? How is your heater fan ground wire over by the fender under the hood? Have you removed all the wires from both firewall mounted buss bars, cleaned everything and made sure they are put back on tight? Does your horn work? The horn leads to all kinds of black magic stuff, so it really is kind of important.

Sorry for answering your question with questions, but it will narrow things down.

 

[wigwag11]

Well to start i did check the ground by the parking brake and all is good there. I did not check heater ground since it was working fine but will. the horn wiring is there and it all works with volt meter, however the horn itself was bad so I have removed until I can get another one. I did not remove the wires from the buss bars but did inspect them and all look good. I will look at these items and see if they solve the problem. thanks for the help though cause I would have never thought the horn would be "black Magic", but I have seen some weird stuff in my days so it doesn't surprise me at all.

 

[MarcusOReallyus]

Well to start i did check the ground by the parking brake and all is good there.

How did you check it? If you didn't take it apart and clean it down to shiny metal, assume it's not good. If there are two surfaces together, take them apart and clean them. Visual inspection is useless.

I did not remove the wires from the buss bars but did inspect them and all look good.

Meaningless. Remove, clean, reassemble.

I will look at these items and see if they solve the problem. thanks for the help though cause I would have never thought the horn would be "black Magic", but I have seen some weird stuff in my days so it doesn't surprise me at all.

That horn circuit is very, very strange. GM did some dumb things with it, and with the wiring in general, and we pay the price. Take a look at the diodes sticky some time to get amazed.

 

[wigwag11]

Ok so here we go I have spent months on this beauty and have cleaned every dang electrical connection and applied dielectric grease to them all. Everything works like a champ now and I have figured out my problem. Alt 2 is bad! so I rebuilt it, replacing every part except the rotor and stator. I even checked the new parts before installing them. However the darn thing still isn't charging. I got all the voltages correct everywhere and all connections are clean or replaced as I mentioned before. So my question really is the stator or rotor bad and can they be replaced, or should I just drop in a new one and forget about the $40 rebuild kit.

 

[MarcusOReallyus]

Stator and rotor can both be replaced. The TM has a section on how to test them.


It's in TM-2320-289-34, Section 4.2 "Alternator testing and repair (all except M1010)"

 

[Rvitko]

I had a very similar issue but gen 1 light would strobe, it was a blown rectifier in gen 1 and this seemed to prevent gen 2 from working properly.

Ok so here we go I have spent months on this beauty and have cleaned every dang electrical connection and applied dielectric grease to them all. Everything works like a champ now and I have figured out my problem. Alt 2 is bad! so I rebuilt it, replacing every part except the rotor and stator. I even checked the new parts before installing them. However the darn thing still isn't charging. I got all the voltages correct everywhere and all connections are clean or replaced as I mentioned before. So my question really is the stator or rotor bad and can they be replaced, or should I just drop in a new one and forget about the $40 rebuild kit.

 

[wigwag11]

Update! I got it all fixed by putting a new alt in the ol girl now she charges like a champ. I will tell everyone though When you buy one of these vehicles the first thing you should do is disconnect every electrical connection, clean it thoroughly and use liberal amounts of dielectric grease! This is a must for tracking down Demons, and it fixes most of them. Thanks everyone for the help on this. Now to the lift and tires, am/fm radio, interior, and A/C.