Went to drive my BMW M5 last weekend and battery light came on on dash. Car started and seemed to run fine(I keep on a CTEK charger) for a few minutes before I turned it off. Manual says battery may not be getting charged from alternator. No other issues or codes. Disconnecting/reconnecting battery, no change. Don't see/hear issue with alternator belt. Need to bring it to the shop, but it is about a 20 minute drive. Can I safely drive it there or should I flatbed it?
Driving car with charged battery but possible alternator not charging
- Thread starter drfeelgood
- Start date
Depending on the condition of the battery you would probably make the 20 minute drive.are you prepared to wait hrs for a tow truck if you don't?
If the car starts, drive it!
I do need to ask something here; can we get a pic of the 1970 Chevelle SS396 and can you give us the story about this car?
Getting back to the car you are having an issue with; I am sure the shop will help you out.
I do need to ask something here; can we get a pic of the 1970 Chevelle SS396 and can you give us the story about this car?
Getting back to the car you are having an issue with; I am sure the shop will help you out.
Test the battery voltage before you start it next, after its been off the charger for a while, if its above 13V, you should easily make it on the battery if you turn off all the unnecessary electrical loads, AC too, as it will kick on the fans. Much below 13, and probably the battery isn't too happy.
Thanks for the quick replies. The shop pretty much said as above, that they think I could make it, "but if your wife or daughter were driving it, maybe flatbed it" LOL. The nearest auto parts store is almost as far as the shop, unfortunately.
This is the Chevelle. I've owned it for 20 yrs. It is a matching numbers L34 with Muncie M20
This is the Chevelle. I've owned it for 20 yrs. It is a matching numbers L34 with Muncie M20
This has to be the best Thread ever on BITOG, we went from a question about a BMW M5 to this Picture.
What axle gears?
I used to deliver propane and one of my customers had an orange 70 SS. The engine and transmission were on the ground... I'm gonna restore it someday is what he said
I've had an alternator belt break where it was down to one rib, so I just took a chance. It did eventually break, but it was weird how it operated just off the battery. It was also driving the power steering pump, so that made it harder to steer. Then the radio died even though I could still drive. I managed to get to the destination where it stopped completely in front of someone's driveway. I kind of limped into a parking space to give room to exit the driveway and the residents were OK when I said it broke down and I was going to call a tow truck.
That was fixed the next day for maybe $125. I also got a rebate for the service (at a Goodyear store) in the form of a prepaid debit card.
That was fixed the next day for maybe $125. I also got a rebate for the service (at a Goodyear store) in the form of a prepaid debit card.
Every mechanic should have a DVM. The basic test of voltage at battery of 12.6V with engine off and about 1V higher or a little more than 1V with engine running is pretty easy.
If the voltage does not go higher with engine running you probably have an alternator problem.
If the voltage does not go higher with engine running you probably have an alternator problem.
It's easy enough to test. The alternators in the bigger cars had cooling provisions, but an E39 predates the the logic-controlled charging found in the stuff today.
Left unsaid is whether the warning light was constantly lit, or intermittent.
I've driven 15 minutes home before, at night with headlights in use, with the light on due to a bad regulator, solely on battery charge. But that was on local roads, at low/moderate speed. Depends on circumstances and risk tolerance whether you might do the same.
Edit: I should also amend that to say, that drive was made with the radio, and other power-consuming accessories turned off; just the essentials.
Edit 2: In lieu of having a voltmeter on hand, the instrument clusters in that era can also display voltage when put in diagnostic mode. As well as with engine running, but you'll have to seek out the details of what the E39 allowed. OBC as well.
Left unsaid is whether the warning light was constantly lit, or intermittent.
I've driven 15 minutes home before, at night with headlights in use, with the light on due to a bad regulator, solely on battery charge. But that was on local roads, at low/moderate speed. Depends on circumstances and risk tolerance whether you might do the same.
Edit: I should also amend that to say, that drive was made with the radio, and other power-consuming accessories turned off; just the essentials.
Edit 2: In lieu of having a voltmeter on hand, the instrument clusters in that era can also display voltage when put in diagnostic mode. As well as with engine running, but you'll have to seek out the details of what the E39 allowed. OBC as well.
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Thanks for additional replies! Regarding the Chevelle, it has 3.31 Posi rear. Makes highway cruising somewhat tolerable.
The M5 doesn't have a voltmeter gauge. And the battery light was on constant, no flickering while running. I do have an older Schumacher charger that I believe would give the resting battery voltage and maybe the voltage after starting. Good thought. Electrical is not my strongest area with auto care.
The M5 doesn't have a voltmeter gauge. And the battery light was on constant, no flickering while running. I do have an older Schumacher charger that I believe would give the resting battery voltage and maybe the voltage after starting. Good thought. Electrical is not my strongest area with auto care.
Radio set to Classic Vinyl (Sirrus XM) is essential
Update for anyone wondering. I checked the battery with the Schumacher, was 12.7 volts fully charged. started car, no upward change and alternator tester on it said zero. Definite lack of charging. Drove the car to the shop today in Friday afternoon traffic with tight sphincter. While waiting at a light, the brake, ABS and traction control lights came on but car kept running and eventually did make it to the shop. Yay!
f355spider
$50 Site Donor 2026
You were lucky. I have owned my 2001 E39 540 (384,000 miles) since new and been through three alternators. First one failed about 25 minutes away from the dealer, while on the freeway...I knew what was up, turned off the radio, headlights, and A/C and drove straight there and almost made it. Died about 1 mile from the dealer. The last two miles I was getting "transmission fail safe" and "engine fail safe" warnings on the onboard status on the dash as well as the "trifecta" you saw. It finally dropped to idle speed and would make no power so I pulled to the shoulder of Interstate 5. AAA flat bed got me the last mile...and surprising the wait was only 15 or 20 minutes for them to show up.
The next two times happened at my house and being only 15 minutes from dealer, I risked it and drove there. E39 5 series are power hogs for their time period and have 140 amp water cooled alternators and 900 CCA group 48/H8 battery. I believe your M5 version has the 120 amp air cooled alternator...maybe because less computers to run an automatic transmission like on the 540.
Its crazy my 2018 M550ix has a 250 amp alternator and two batteries, 950 CCA group 49/H9 and a 670 CCA group 47/H5 battery.
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On a late Friday afternoon, I left work in the Legend when the battery light came on as I got onto the freeway. Dead alternator...again. I got as far as Livermore (35 miles) before the headlights were too dim to safely continue. I left the car in the Best Western parking lot before starting the climb up over Altamont Pass. I was still 15 miles from home.
While I was waiting for the wife to pick me up, I removed the battery from the Legend to take it home to charge overnight. I returned the next day, re-installed the battery and made it the rest of the way.
Just another adventure.
While I was waiting for the wife to pick me up, I removed the battery from the Legend to take it home to charge overnight. I returned the next day, re-installed the battery and made it the rest of the way.
Just another adventure.
