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Discussion Starter · #1 ·
My car has an issue whereby the alternator will not run at all at cold start, however after setting off or even revving the engine to around 2k rpm it will begin charging. This is accompanied by a rough cold start where the rpm's sort of swing up and down and the car feels like it will stall before smoothing out (see my previous posts for a video) and a charging fault error on the iDrive screen.

I thought this may be to do with the battery, as the car had a regular lead-acid (not AGM) which had not been programmed into the car correctly and was also below the rated spec for what these cars need. I replaced it with an AGM which I registered with the car (it was already programmed for the nearest capacity AGM to what I got).

The issue only occurs on cold starts and I've had no trouble at other times, even when the car has been parked for a decent amount of time. Could this be a voltage regulator issue as these cars are known to have, or is it the alternator itself or something different altogether?

This is the code it's logging in ISTA
Rectangle Font Line Screenshot Parallel
 

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Yeah, i saw that video you had posted. I had commented also, it definitely looks like electrical issue. A bad voltage from the battery terminals can muck up all the electronics.
This morning, I got a Trans fail Red cog also, and it cleared up immediately. A bad electrical voltage will NOT operate any of these modules and pumps; and will throw up all kinds of meaningless errors.
 

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Discussion Starter · #5 ·
Yeah, i saw that video you had posted. I had commented also, it definitely looks like electrical issue. A bad voltage from the battery terminals can muck up all the electronics.
This morning, I got a Trans fail Red cog also, and it cleared up immediately. A bad electrical voltage will NOT operate any of these modules and pumps; and will throw up all kinds of meaningless errors.
So far I've not had any other issues to speak of, it seems like it's just an alternator issue. Interestingly, in that previous post I made when I had the old battery the car was also throwing an alternator communication code however that has now gone away and I've not seen it again with the new AGM battery
 

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Well lets see, start at the battery. When my car went dead the bolt on the clamp was tight but the clamp was not seated on the battery so I pulled it off with my hand. Just give it a good twist to make sure it is tight. Then you have all the bolted connections including the grounds. I think one goes to each side of the car. Then you have the little do dad that I can remember the name of that blows the connection in a crash. Then you have to got up to the left side of the engine for the big connection by the Ionic module. The grounds are important too. Then to the alternator connections. If I am not mistaken there is/was a recall for the cable from the battery to the engine. With problems like this 90% of the time it is a loose connection and a PITA 100% of the time to locate.
 

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What sort of connections?

Everything runs fine after cold start so I'm doubtful that something isn't plugged in correctly.
In my case, I don't even move the car. The cold start doesn't charge battery. Wait for 2 mins and re-start the car, everything works fine. Doesn't sound like any connections.

I took it on a 200 mile drive, starting stopping multiple times, and came back 200 miles. Ran clean. But while at the hotel, next morning, cold start again shows battery not charging :D
I have Torque Pro on my android connected all the time to my car, and I strictly monitor battery charging, cylinder misfires, and O2 sensors all the time during my drives.
 

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Discussion Starter · #10 ·
Could this even be a computer issue or something that one of the modules is causing to happen? One thing I know with my car is it has been jumped from the battery itself a few times and once even with two jump boxes at once (one at the engine bay and one at the battery) by a tow truck driver. Maybe this somehow screwed something up and is causing this issue? That said, if it had blown the CAS or a fuse or something I'd expect it to stop the car from running at all.
 

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Could this even be a computer issue or something that one of the modules is causing to happen? One thing I know with my car is it has been jumped from the battery itself a few times and once even with two jump boxes at once (one at the engine bay and one at the battery) by a tow truck driver. Maybe this somehow screwed something up and is causing this issue? That said, if it had blown the CAS or a fuse or something I'd expect it to stop the car from running at all.
In all likelihood, dying regulator lol, nothing complicated. Its trivial to swap just that part and see if it cures the problem.

When left in the cold, its probably altering the regulator properties, and after a bit of Warm up, the electronics works good.
 

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What sort of connections?

Everything runs fine after cold start so I'm doubtful that something isn't plugged in correctly.
Bad ground connections can also make the car do funny things. Give those a quick once-over to make sure they're clean and tight. The braided ground straps can corrode over time and even break.
 

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Discussion Starter · #13 ·
In all likelihood, dying regulator lol, nothing complicated. Its trivial to swap just that part and see if it cures the problem.

When left in the cold, its probably altering the regulator properties, and after a bit of Warm up, the electronics works good.
How difficult is it to replace the regulator without taking off the alternator?
If it's not too tricky I might order one and do it myself or get my mechanic to put it on when the next service is due.

To diagnose it better, can you look at the voltage while driving via the 'secret' menu in the gauge cluster? If it was bad I'd expect to see some evidence there
 

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@TassieBMW and @sunilshivaram, tab on the head of IBS with a mallet 2 to 3 times and check.
But first cycle the connectors at that area, check no wiring insulation degradation of the IBS at the IBS itself and at the connector to the car.
@TassieBMW, the car throw a code but if the code happened after the cold start or because the alternator didn't charge after certain conditions set by the DME, I would ignore it until I give it some troubleshooting. It could be the alternator if it fault consistently not only on cold start. Do the IBS trick and check then go from there.
 

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I will follow your thread with interest, hopefully we can find a solution!
Only difference with my issue is there is no whine, the RPM's just jumps around in a weird way on cold start.
Mine was the same
Alternator replaced
As i couldnt get a voltage reg locally it seemed stupid to wait for one from germany when i could get a whole new alternator next day
 

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Discussion Starter · #16 ·
Mine was the same
Alternator replaced
As i couldnt get a voltage reg locally it seemed stupid to wait for one from germany when i could get a whole new alternator next day
So that solved it?

If so I might order a reg. I don't drive the car much and overcoming the issue on cold start isn't a big deal so happy to wait a few weeks for a part.
 

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If so I might order a reg.

My voltage regulator was replaced 4 years back - i had plugged in a used one from another ebay alternator that I managed to get for $0.
But I want to make sure its definitely the regulator, I also don't drive much and the car can wait it out. In my case, there was a very loud
whine on cold starts, only on cold starts, and the whine is now gone. I will take all the parts apart and try to check them individually. Its
still a mystery to me why this issue manifests only on cold starts.
 

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How difficult is it to replace the regulator without taking off the alternator?
If it's not too tricky I might order one and do it myself or get my mechanic to put it on when the next service is due.

To diagnose it better, can you look at the voltage while driving via the 'secret' menu in the gauge cluster? If it was bad I'd expect to see some evidence there
There are some pictures where it was done without taking out the alternator; i think as long as you can have line of sight to the regulator and the bolts holding it, it can be done.

The voltage isn't in the secret menu to the best of my recollection. I do use Torque Pro on my Android Phone with a BT OBD2 scanner, to stare at the voltage and few other monitors all the time while driving. The battery gets charged after a slight warm up. Again, i do suspect its the regulator electronics that is going bad and it appears to be the cheapest option to replace and try.
 
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