Now the Alternator

[RBBailey]

Now that it's dark enough out in the morning, I have noticed that my battery light is slightly glowing. This morning, it was glowing faintly, but coming on a bit more as the wipers went on and off. The voltmeter is showing about 12.5 while driving...

Now, since I'm running LED park lights, head lights, and bumper lights, and since I only drive 6 miles each way on my commute, I can make this last a while by putting the battery on a charger every night. However, I still have not figured out what is going on with the voltage drop to the starter, so I'm already push starting or hot wiring every other start cycle. This is an annoyance on what is already annoying.

So before I pull the alternator and get it rebuilt, (it only has 14k on it) is there anything I should look into as possible causes here, other than the alternator itself?

 

[xplorutah]

This is frustrating. I am working through similar on my series. How are the battery cables and such? Any corrosion that you can see? Any you can’t? I am by no means an electrickery guru. These are just some things I have addressed while chasing a similar issue. Good luck! Drew

 

[NPT90]

Now that it's dark enough out in the morning, I have noticed that my battery light is slightly glowing. This morning, it was glowing faintly, but coming on a bit more as the wipers went on and off. The voltmeter is showing about 12.5 while driving...

Now, since I'm running LED park lights, head lights, and bumper lights, and since I only drive 6 miles each way on my commute, I can make this last a while by putting the battery on a charger every night. However, I still have not figured out what is going on with the voltage drop to the starter, so I'm already push starting or hot wiring every other start cycle. This is an annoyance on what is already annoying.

So before I pull the alternator and get it rebuilt, (it only has 14k on it) is there anything I should look into as possible causes here, other than the alternator itself?

300TDI?

There is an easy swap equivalent, I believe it had the bottom hole threaded so you may need to drill it out. There are also 2 different pulley sizes for the belt, a smaller diameter and a larger one, they actually use different belts (I happen to have one for the smaller pulley if you need it)

iskra 100AMP

 

[RBBailey]

Yeah, it's strange how the Series just keeps going, all my other Rovers just keep going. But this thing is having failure after failure within the first 15k miles. I would be driving the Series this week, but it's soaking wet out, and for some reason when I treated the canvas it started leaking really, really badly.... so I have to figure out a time to get the hardtop rebuilt before I can stop driving the Defender long enough to fix all the issues I have with it.

Yes, it is a 300Tdi, so that's a plus in this case. All cables and such are clean. I'll take the time to check for anything that is loose on the alternator when I get a chance. But yeah, it only has 15k miles on it.

 

[rocky]

I had a similar conversation with the owner of a shop last week. Replacement part quality in recent years gone towards junk status.
He replaced the alternator on his wife's minivan a month ago. It's failed already.

 

[RBBailey]

300TDI?

There is an easy swap equivalent, I believe it had the bottom hole threaded so you may need to drill it out. There are also 2 different pulley sizes for the belt, a smaller diameter and a larger one, they actually use different belts (I happen to have one for the smaller pulley if you need it)

iskra 100AMP

That looks like a good match, but can I swap pulleys? Are the grooves a match? Are you saying that I might get one with a larger pulley, or a smaller?

 

[Napalm00]

The reason your starter is acting up is because the load that the starter is trying to put on the nearly flat battery and non-charging alternator is causing it not to function and showing that drop to 9ish volts.

The smaller the pulley the quicker you achieve charging amperage on the alternator. on a TDI you can guarantee you will never spin it fast enough to damage it so put the smallest pulley you can get.

 

[RBBailey]

The reason your starter is acting up is because the load that the starter is trying to put on the nearly flat battery and non-charging alternator is causing it not to function and showing that drop to 9ish volts.

The smaller the pulley the quicker you achieve charging amperage on the alternator. on a TDI you can guarantee you will never spin it fast enough to damage it so put the smallest pulley you can get.

Battery is sitting at 12.7 volts overnight. It is only a month or two old, and I charge it every week. It is a deep cell marine battery, so I put it on a smart charger. But I have wondered about this as being a part of the start issue. However, the start issue shows up with or without the battery connected to a charger. It sometimes does better with a charger attached because I can watch the 7.5 volts turn into 9.5 volts if I hold the key for 10-15 seconds. It starts very well once it gets about 9.5 volts. Today, I started it by jumping to the solenoid on the starter. It instantly fired up with the 12.3 volts from the battery being applied directly to the solenoid.

It was not charging when running. So I headed straight home and didn't see any change the whole way. When I got home I left it running, and put a volt meter on the battery. It showed 12.3 volts while running. (This is after two start cycles, and running with fan and lights on for that time, then sitting for 9 hours in 50 degree temps.) When I opened up the hood and checked for any loose wires on the alternator, I found none, but it did start charging. The battery shows 13.7 volts while running, and it bounces between 13.5 and 14 volts depending on revs and on whatever load I put on it.

I don't know why it started charging when I began to look at it.

 

[RBBailey]

So.... this basically means that my 300Tdi conversion is set up wrong. What battery/alternator/starter combo should I use? I'm running with the Magnetti 100amp, a 12v 600 cca deep cell marine battery, and a standard Bosch starter. Where did I miss the memo! I've used this battery in my Disco for over five years without problem. And the Alternator, battery, and starter all have less than 15k miles on them. The battery is only three months old.

 

[Napalm00]

No the setup is fine . You alternator sounds bad

 

[Napalm00]

It should charge at 13.xx volts maybe a hundred rpm above idle.

You were getting starting issues because the battery was discharged.it needs to be slightly above or at 12v when the truck is off to be healthy.

 

[RBBailey]

I just let the battery charge for a bit, then started the engine. At first, it was not charging, but then seemed to jump into action. It shows just under 14 volts when charging. This is where it always seems to be. Seems like it is an intermittent issue, like it is on its way out. I have to get back to work tonight, but when I get a chance later this week, I'll test and retest the charge while running the engine. But yes. It seems like the alternator is going bad.

The problem with the theory that the battery being drained is the reason I'm having start problems is that I've tried four different batteries. The one I currently have in it is only three months old, and when I installed it, the vehicle was currently not starting. I unbolted the old battery, put the new battery in it's place. Nothing. I decided to keep the new battery anyway since the old one was testing at just barely still good. The other thing is that when I jump (run a clean wire directly from the + to the solenoid) the starter with the same battery, it turns just fine. The problem I'm having starting always comes back to the start circuit. I've tried starting it while the battery is fully charged, and connected to a 15 amp charger. Same results.

 

[rocky]

So your alternator isn't charging until you rev the engine?

 

[NPT90]

That looks like a good match, but can I swap pulleys? Are the grooves a match? Are you saying that I might get one with a larger pulley, or a smaller?

Yes, if you get it from a local shop they will do it for you, the groves are a match, you will get one with a smaller pulley, yours might be bigger (later 300TDIs came with the smaller pulley to lower RPM consumption). If you have a small pulley it is plug and play.

There is also the issue of the charge wire coming off the alternator, it goes to the starter lug then on to the battery.

Sometimes these are undersized, sometimes these are melted or otherwise damaged. I added an ancillary wire along the harness in I believe 8 gauge to help under heavy draw (though my truck is all LED so the highest draw I have is the battery charging). though it seems undersized according to this chart:

it's important to remember the run is less than 4 feet and the actual current (though rated at 100amps) will only be what the vehicle is pulling (300tdi is minimal) and the battery charge load (start amperage drop being the primary draw).

 

[NPT90]

I just let the battery charge for a bit, then started the engine. At first, it was not charging, but then seemed to jump into action. It shows just under 14 volts when charging. This is where it always seems to be. Seems like it is an intermittent issue, like it is on its way out. I have to get back to work tonight, but when I get a chance later this week, I'll test and retest the charge while running the engine. But yes. It seems like the alternator is going bad.

The problem with the theory that the battery being drained is the reason I'm having start problems is that I've tried four different batteries. The one I currently have in it is only three months old, and when I installed it, the vehicle was currently not starting. I unbolted the old battery, put the new battery in it's place. Nothing. I decided to keep the new battery anyway since the old one was testing at just barely still good. The other thing is that when I jump (run a clean wire directly from the + to the solenoid) the starter with the same battery, it turns just fine. The problem I'm having starting always comes back to the start circuit. I've tried starting it while the battery is fully charged, and connected to a 15 amp charger. Same results.

Hate to say it again, check the starter lug for connectivity problems. Could be the starter positive post is broken off or otherwise damaged internally or that nut has backed off to the point of intermittent start issues (though I am sure you have been through this area tons of times).

Local autoshops can bench test your alternator. There is a 3rd option that I have considered but not yet executed:

Moving the charge from the alternator, and the main fuse power feed off the starter to a remote bus bar. Effectively eliminate the positive terminal on the starter as the main distribution point for 12V for the rest of the system.

I don't really see a reason to keep the main power feed and the alternator charger on the starter lug which seems overly crowded as it is.

 

[RBBailey]

So your alternator isn't charging until you rev the engine?

Doesn't charge no matter what. Unless it is charging, then I can see the voltage bounce a bit when it is revved, but it stays at 13.7-14.0 no matter what.

Example: Yesterday, I drove to work, and during the drive it charged for about 30 seconds, but the rest of the time it was not working. On the way back, it never showed a charge at all, but after I got home I left the engine running and by the time I came back out to use the multimeter on the battery and such, it started charging as normal.

I'll double check everything again today. Problem is work gets in the way, and I don't have the time to dedicate to this type of thing. Might be a while.

 

[Napalm00]

After you start it it may take a few seconds for it to start charging. What you're describing is most likely either a bad alternator or some bad wiring . Once it starts charging it should stay charging for the entire time the truck is running.

Check all the connections, upsize the charge cable from alt, starter, battery if needed

The alternator being knew doesn't mean Jack, local guy here has been through three Bosch 100 amp alternators on his truck in under a year. Quality isn't there anymore

 

[1of40]

I had a similar conversation with the owner of a shop last week. Replacement part quality in recent years gone towards junk status.
He replaced the alternator on his wife's minivan a month ago. It's failed already.

Last week my alt started to act up out as well. I was about an hour into a road trip so I turned around and headed to a shop I knew would have a rebuilt unit. It lasted 3 days. I ended up swapping it for one pulled from a parts truck and my fingers have been crossed sense.

 

[javelinadave]

In my humble opinion the factory wiring harness is a bit undersized. As the wiring gets older and the wire strands oxidize or start to corrode their resistance increased. For the swaps I did I would make a new harness from the main harness plug to the different points on the engine. Takes 10 minutes to make and I never had ANY electrical problems.

 

[RBBailey]

What did you do to splice into the plug with your new wire?

And did you route the wiring through the maze, and through the bulkhead? I have to take half my dash apart just to put a multimeter on the ignition switch.