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View Full Version : Electrical gremlin, battery light... HELP



Absolutjh22
04-10-2013, 03:25 PM
2001 E38 740i Sport 80,9xx miles, build date 03/2001, build code GG83

So my 1yr old remanufactured-alternator died a few weeks ago...

Step 1: Replace Battery (done)
Step 2: Replace alternator (done)
Step 3: Replace all applicable H2O gaskets, Valley Pan, Intake Manifold gaskets, O-Rings, Oil breather tube & gaskets (done)
Step 4: Replace coolant, purge system, replace radiator cap (accidentally closed the hood on it), confirm coolant levels (done)

Here's where the gremlin comes in.

My battery light will flicker on/off at idle and the new battery does not seem to maintain a full charge. Voltage reads 12.75v at jumper post of engine bay and 12.25v at battery. I get a very small metallic sound at start-up, which immediately goes away.

I have on-hand the Adjusting Pulley Tensioner #11-28-1-709-613-M40 however I'm unsure how to test the old one to know if it is shot?

I am considering that the bearings on the adjusting pulley tensioner assembly are going bad, however when I did the above mentioned work I spun the wheels and they seemed to spin with no adverse friction.

Of note: after re-assembly I was getting the "check coolant level" message so I bought a new sensor thinking that the 3 yur old one may have died. Went to put it in last night and found that I had failed to reconnect the old sensor. After reconnecting the coolant level sensor the message went away. Sweet. However, when testing the voltage prior to reconnecting that sensor I was getting a reading of 11.6v, after it was reconnected I am reading 12.75v. Hmmm... So I put the new battery on an automatic charger at 10 amps, and left it on overnight. Charger indicated FULL this a.m, however upon start-up the battery light flickered on/off until I revved the engine above idle.

I am hopeful that its just the tensioner, but maybe I am missing a relay etc somewhere that one of you can point me in the direction of. I am driving this car to Colorado, with my 6 year old daugher, on Friday and would like to feel as though the car is sorted prior to leaving. If its not sorted out soon, I'm going to throw-in the towel and sell this money-pit of a car. I hate to say that, but it seems that these "common" problems should have been sorted out by BMW engineers. There is no reason a $70,000 car should continue to have so many issues, especially in its final months of production.

Any helpful input would be appreciated.

Thanks in advance.

Timm
04-10-2013, 03:45 PM
The battery light is independent of any relay, if the battery light illuminates it means the alternator is faulty, or not turning fast enough to produce a charge. It is certainly worth replacing the tensioner - but I would expect squealing and smoke if it was slipping (unless the belt is contaminated with oil).

xboss
04-10-2013, 03:53 PM
Double check the loop. Check the Alt wires, make sure they are clean etc. Check the battery cables, make sure they are tight and clean. Check the battery drain when the car is turned off and sleeping.

Absolutjh22
04-10-2013, 03:53 PM
The battery light is independent of any relay, if the battery light illuminates it means the alternator is faulty, or not turning fast enough to produce a charge. It is certainly worth replacing the tensioner - but I would expect squealing and smoke if it was slipping (unless the belt is contaminated with oil).

TIMM - Thank you for your input. I guess I'll start with replacing the tensioner since I have it, and I'll give the belt a good cleansing just in case. Would it be very obvious that the tensioner has gone bad? Is there a way to dignose the condition of the tensioner? I am unable to get the belts to squeal even under load (revving the engine with all systems on).

Absolutjh22
04-11-2013, 08:09 PM
So I replaced the belt tensioner and confirmed that the bearings in the tensioner bracket are working just fine (no grinding or movement). The voltage output came up about 0.75 volts from previously in the day. Unfortunately, the battery light is still flickering on/off. I presume that this light must measure the amperage output from the alternator? Either way, I think it's time to consider a change...

dazednkenfused
11-25-2013, 03:20 PM
I'm having the same problem, was this ever resolved?