Battery light came on a week ago for a few minutes. I stuck the gauge in and started watching voltage and everything was fine with no more issues or lights until yesterday morning. Then I had less voltage with the truck running then with it off. No voltage at all from the alt.(and the battery light came back on). So I waited till Autozone opened up and got my "lifetime" alternator swapped out for free. Stuck it in and was on my way.

130 miles later that afternoon, the battery light comes on again and I'm showing 13.3 volts. So I swing by autozone to get it checked and they find a dead cell in one battery. We have the discussion about how diesel batteries should be replaced in pairs so they decide to give me 2 new batteries for a warranty exchange. Change them in there parking lot and as I'm leaving, the battery light comes back on. Get the alternator tested and it shows pass. I also had them bench test the alternator before I took it home the first time to be safe.

Still showing 13.65 - 13.85 volts while driving around. Hooked up jumper cables to a tractor last night and voltage jumped to 14.2. Cleaned the cable connections. Battery light still comes on and goes off rather frequently. RPM's have no effect since it often comes on when cruising down the freeway.

Suggestions or thoughts as to what's going on? For the record, the alt. & battery combo lasted 2 years. The stickers on the old batteries were labled 7/08. The stickers on the new batteries are labled 7/10.

 

Might not have any effect at all....but have you checked the cable connection at the starter? Maybe it's a little loose?

Just taking wild stabs just in case you didn't already think of this.

 

possible a bad ground at the block, maybe loose or corroded. Other than the starter connection, im scratchn my head.

 

I'll double check the connections, but I'm not having any symptoms other than the light on the dash. I've been watching the voltage reading while driving and it's not jumping around or acting funny when the light comes on, and it doesn't do anything different if the light goes off 10 minutes later.

I'm guessing it's one of those internal gadgets in the alternator and not a voltage issue. If I start seeing fluctuating voltage, I'll get it swapped out, but so far it seems to be acting normal on the voltage side.

 

You mentioned before that you were having problems with your AC. I wonder if that could have anything to do with it? Maybe try to unplug the ac electrical connector. Have you gone through all your fuses? There is also a diode for your ac clutch that you might want to check. Listed as #37 in the engine fuse box in my owners manual. Sounds like it might be a pain to track down. Just throwing out some thoughts.

 

All I can suggest is to go thru all your connections to the batteries, starter and grounds and make sure the are clean and the cables are in good shape. May be worth testing the cables, even through they have continuity they may not be in shape to carry the required current.

 

where are all the major grounding points?

 

I guess I got lucky. My battery light = dead alternator.

 

Check the connector that plugs into the alternator Chris. Like I said earlier on my way back from TN my battery light did the same thing. I pulled over and cleaned the battery clamps and posts. All set. Drove approx another 50 miles and the same thing happened. We pulled over again thinking that I needed to get batteries after the alternator incident, it turned out that upon wiggling the connector the voltage would jump from anywhere from 12.1 to 14.2 volts. I ty wrapped the cable to take any pressure off the connector and it has been fine ever since.

 

I feel like I might have the exact same problem as you and mine just started 2 days ago. Came on and went off pretty quickly the first day, then stayed on the whole next day. Today I go check voltages at the batterys and the alt and get the same reading, lower voltage with the truck running than with it off. WTH??? I also saw where someone posted you having A/C issues, I am having some of those too so I'm going to go find that thread as well. This SUCKS, its HOT in San Antonio with no A/C!!! LOL Let me know what you find out, I'm gonna take this to the brand spankin new autozone and have it tested and probably throw a new alt at it.

Nick

 

Might want to try something like Dan did. Check out post number 5
link to other forum post

 

Is this a re manufactured alternator? Why don't you sweet talk the wife and swap.....

 

Thanks Jim. I started playing with that but my AC guy called so I got side traced with more important issues.

I had to replace the clutch on my AC. It's been working flawlessly since. Of course the AC on my house is dead right now. Dealing with the truck AC was much easier.

I've been thinking about that, but am not sure it will help my situation. Like I said, I'm not getting any fluctuation in the voltage readings.

She'll probably make me clean my engine before I'm allowed to put it in, but that's a pretty good idea. I might try that and see if it helps.

 

on the up side it's cheap and it couldnt hurt...wish I had some better insight.

 

Ah, the home AC, that sucks way worse than my truck ac being out. Good luck!

I was reading somewhere else that the truck AC may have issues if the clutch is old and the voltage drops too low. Hoping I don't have to replace both right now.

You having pretty good luck with the autozone alt other than this incident? Cant decide if I want the autozone one or the oreilly one even though I know they probably both come from the same manufacturer.