Bad alternator, or is it?

[Napoleon_Tanerite]

So a few days ago I noticed that the the volt meter on my M1009 was indicating about a needle width into the yellow band. I checked the voltage at the batteries, and sure enough the voltage at the forward battery was at 12.4 volts, with the alternator at the driver's side indicating the same. Seems like a clear cut case of a bad alternator, but I'm not sure, and here's why:

No Gen 1 light. Light checks good on startup, and remains out EXCEPT for last night. Last night I had a 1 hour drive back from my hunting spot, and the Gen 1 light illuminated faintly (visible in dusk light, no more than maybe 50% brightness at its peak) for about 30 minutes of the drive. The strangest part was it got BRIGHTER at high RPM, and then dimmed to being completely out at idle. After about 40 minutes of driving the light was completely out at all RPM ranges.

I definitely have some sort of battery issue-- truck wouldn't restart on the extended crank required due to my current fuel/starting issue. (could use help with that too).

 

[idM1028]

Best bet would be to take it out and have it tested. I had the same problem with my GEN 1 light coming on at high RPM's and going out at idle. Turns out theres a small connector near the GP resistor bank at the back of the engine bay. I popped the pins out and cleaned them since they were disgustingly dirty and corroded. Haven't had any problems since, but I also d*** well near replaced everything in the charging circuit for GEN1. Lots of work and lots of $$$

 

[acesneights1]

clean all terminals and grounds too.

 

[Jerchambers]

Best bet would be to take it out and have it tested. I had the same problem with my GEN 1 light coming on at high RPM's and going out at idle. Turns out theres a small connector near the GP resistor bank at the back of the engine bay. I popped the pins out and cleaned them since they were disgustingly dirty and corroded. Haven't had any problems since, but I also d*** well near replaced everything in the charging circuit for GEN1. Lots of work and lots of $$$

What connector are we talking about? I am having similar problems. I was going to take my alternators to my guy tomorrow and have him bench test them, however if I can try some other things it would be great.

 

[Napoleon_Tanerite]

Agreed. I am lost working on most aspects of this truck, but pick up quickly with pictures or direct TM references.

 

[Warthog]

.... Turns out theres a small connector near the GP resistor bank at the back of the engine bay. I popped the pins out and cleaned them since they were disgustingly dirty and corroded.

Did you take pictures of this connector? Can you post pictures? I'm sure it will help many others.

 

[Barrman]

Napolion, where you runing your a/c this entire time the light was glowing? Don't forget that the heater fan gets its power from the fuse that excites the #1 alternator. That light will light up partially if the headlights are on and the heater fan is on high.

I suggest taking the alternator apart and bench checking each component. After you have verified it is an alternator problem and not a truck wiring fault.

 

[blackhueys]

similar issue as what I had. I had both rebuilt still same issue well got bored one day and popped one open as I don't trust any ones work any more and what did I find? they never replaced my voltage regulators. Spent 30 bucks for two new ones and about an hour total of work now I am way up in the green right on the line as a matter of fact and about 14 volts plus on either alt now as well. Not sure if that's your case but after my spending hours trying to figure it out it was just 2 small parts!

 

[M1008driver]

One time I thought my DS alternator was not charging the front battery correctly. While disconnecting the negative cable I pulled on it and it came loose. I got a new connector from the battery shop because they have the right crimp tool and it only cost me $8. I also cleaned all my connections on the firewall.

Probably not your problem, but I would give the cables a tug to see if they come loose. My battery cable was rusted underneath the connector too, so the shop snipped it off to get to the good wire.

Edit- My voltmeter always stayed in the high yellow and never past the yellow/green line. Now it goes to green when I start the truck and the gp cycle is finished.

I also left my lights on all day while hunting. Now I have a jump starter behind the seat along with some very good battery cables. It can be used on the front battery in a jam.

 

[stampy]

Clean all of your connections and lube with dielectric grease scrape grounds until the metal shines and scrape or replace fuses. This fixed almost all of my electrical gremlins.

 

[stampy]

Oh and mine charges at about 28v across the batteries but sits dead center between the yellow and green at full charge, and only wanders into the green when having to "recharge" the batteries.