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Battery charging issue please help!

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1.5K views 4 replies 4 participants last post by  grs1938  
#1 ·
I bought my 2000 well kept 2 owner German Disco TD5 with auto trans this year middle of march. The Battery was ancient and very dead so to drive it home i bought a new Varta 70 AH battery since it was the only left positive i could find and i needed to get home. A while ago i started getting strange lights coming on and going off without reason so after reading a few forums i decided to buy the right size battery to make sure i have enough juice. For a while everything was great but one day when i stopped in the heat and left the car on a lot with the a/c on for my dog the dash lights started acting up again. This time the auto trans S and M lights flashed and the car went in safe mode so got really really slow. When i stopped to check it out it wouldnt start again and only showed 11.4V on the multimeter.
After a jumpstart i went home charged up the battery and started checking over things.
Bottom line is now i have a voltage monitor in the car and what happens is when i put a fully charged battery in as soon as its attached to the car the voltage goes down0.3 V
The car works fine but the alternator doesnt charge at idle at all but as soon as the vehicle is revving up and driving the voltage goes up in the 13.8 to 14.1 range. since i live just outside of town as long as i drive it and not sit in stop and go traffic it only gradually looses voltage over time.
Does not drain while parked and has no problem starting even at 12.1 or 12.2

Just guessing thet the voltage regulator might be a logical start but if i remove the alternator from an 18 year old truck with 160k miles or so id be an idiot not to overhaul the whole thing.

please let me know if im on the right track or if there is something else i need to know about.

Really appreciate the help, i plan on keeping this truck a long time so i would really like to take care of the issue the right way.

P.S.
If you are familiar with electronics on this truck read my next post as well please.
 
#2 ·
Denso alternator and replace the thing if you can since you don't know bearing issues and whatnot. (Crap, I don't know if TD is different but it can't be that hard to find)

That issue screams voltage regulator/alternator however with the uncertainty of the part involved I suggest replace

If you haven't replaced it or are unsure when then the usual suspects need to swept.

Keep at it!
 
#3 ·
And FWIW, I get random M+S lights however i am under the impression that my negative connection to my battery needs an overhaul as it's tightened as much as possible however it's easy to get loose.

Great catch on getting voltage.
 
#4 ·
..... Bottom line is now i have a voltage monitor in the car and what happens is when i put a fully charged battery in as soon as its attached to the car the voltage goes down0.3 V. The car works fine but the alternator doesnt charge at idle at all but as soon as the vehicle is revving up and driving the voltage goes up in the 13.8 to 14.1 range.....
Szia Gabor ;)
Replace the alternator ASAP with a new one cos you'll kill the new battery too then inspect and troubleshoot the existing alternator and if you can fix it keep it as spare but don't play with repair kits now cos it can be a winding issue too