alternator confusion

[blindowner]

Hey There
Okay, I bought this truck off government auction, and
it came with both genartor lights on. I replaced gen 2 and the light went off, then I replaced gen 1 but the light stayed on. This is where the confusion begins, I tested the plug and found continuity between the pins. So I replaced the plug with a brand new one , but once I had cut the old plug off, I decided to test the wires for continuity. At first I found none, but I decided to switch the way the wires and test leads were arranged, only to find continuity. I shrugged it off thinking that maybe that was the way it was suposed to be and started the truck, only to find that gen 1 light was on.
So I got a voltmeter and set it for 20 volts and the alternator read 19.50 volts, then I set it to 200 volts and it read around 48 volts. Right now I am exasperated, confused, and discouraged, as such, any help is extremely appreciated and I will be more than happy to answer any questions.

Blindowner

 

[blindowner]

Hello
I thought I should mention that there is continuity between the 12v engine wiring harness block and the positive terminal board. As stated earlier any help , suggestions, and questions are greatly appreciated.

Blindowner.

 

[Barrman]

Did the wires perform as they were supposed to with the plug off?

 

[blindowner]

I am not completly sure what you mean, but if you are asking if the gen 1 light goes out while the engine is running and the alternator plug is unplugged, the answer is yes. If that is not what you mean , can you be a bit more specific . On another note, in the charging circuits wiring diagram, a splice is shown, do you know where the splice is located physically?

Thanks!

 

[Warthog]

What did you replace the GEN1 and GEN2 with? Where did you get them?

When testing the 2pin plug at the alternators, you are not checking for continuity between them. Each of then is a voltage source. You need to be testing for voltage.

Here is a simple test.

Remove the plugs from both alternators. Batteries are hooked up. Using the frame as a ground. Key off for first part of test. Key in run position for second part (NOT RUNNING)


GEN1
the red wire will show 12v at all times
the brown wire will show zero volts with the key off and 12v with the key on.

GEN2
the red wire will show 24v at all times
the brown wire will show zero volts with the key off and 24v with the key on.

If you have these readings the the cab portion of the wiring is okay and the problem is under the hood.

If you don't have these readings the there is an issue in the cab wiring that needs to be addressed before you can test futher.

You asked about a splice. Without seeing the diagram (or description of which area of which diagram we will only be guessing.

Also don't unplug the 2 pin connector when the engine is running. You can damage the internal electronics.

 

[blindowner]

I performed the tests that you outlined and everything was as it should be.
You said that running the truck with the alternator plug unplugged could damage the wiring harness. How could it damage it and hiw can I tell if it has happened and if it has happened, how do I repair it? You also said that you didn't know what splice I was refering to, please refer to the included file
(it is near the center)

Thanks!

 

[blindowner]

Oh! I forgot. THe driver side alternator is an auto zone part number DL7157 and the passenger side alternator is (this is off of the alternator housing) 1105500 100a 6h06 12v.

Thanks!

 

[Warthog]

Okay your cab wiring ans dash lights are okay.

The slices are the the round black barrel connectors that connect the fusible links to wiring harness. Some are at the 12v Positive Terminla Block (diamond shaped connector next to the master cylinder) and the others are at the 24v Positive Terminal Block behind the rear battery.

I'll post some more tests for the alternators a little later.

What I said or ment to say is don't pull the 2pin plug with the engine running. It can send a spike to the alternator regulator and rectifier and burn them out. Won't happen all the time but is possible to damage them. Just ruinning the engine with the unpluged is okay.

 

[blindowner]

Hello again,
I just wanted to inform you what the problem was, I really found it by pure luck, I went out to look for the splice near the 12v terminal board, and I saw a main alternator feed wire that was severed. It appears that the previous owners had replaced the fusible link and done a terrible job splicing it back together. So I bought a replacement wire and soldered it back in and the dash light went out and the truck appears to br charging properly.

Thanks Y'all

 

[AlexFolino]

Not to hijack this thread but ive been having charging issues for a year now since i bought it hence why i can only drive it when i charge the batteries. I did the warthog test listed above and Im getting 24v at GEN 2 red wire but on the BROWN wire 0 with key on or off. GEN 1 is 0 on both wires either way. The truck after charging it and starting it will show 14.5 or so volts at each alternator and about 25v across the batteries. Both batteries are new. If you let the truck sit more than 3 hours its stone dead.. (im lost)

 

[doghead]

Have you rebuilt your alternators? It sounds like they may be the source of your battery drain. They can charge and still be bad. Spend $100 and rebuild them both. CUCVelectric has kits.

 

[AlexFolino]

Thats what im going to do, order rebuild kits tonight. Then go over the wiring diagram for the charging system and rewire everything related. Just looking at it now some wires dont go to where they should and there are one or two thick wires just cut and going no where coming out of main wiring harness. When i start the truck or just have the key on the GEN 2 never comes on and the GEN 1 light does and goes off as soon as you excite it.

 

[AlexFolino]

Where are these circled components located on the truck, thats one of the problems im having understanding or atleast locating?

thanks!

 

[doghead]

The circled items are under the dash, between the radio delete panel and the ash tray.

The ovaled items I think is the plug at the firewall, near the fuse box.

 

[AlexFolino]

I hope its not that big junction block plug at the firewall underneath the master cylinder, ill need a sandblaster to
clean the gunk of of it to see the wires.

 

[doghead]

I think that's it!

Someone correct me if I'm wrong.