cars idling is dodgy after changing battery ?

Post Sat Aug 22, 2009 6:58 pm

i got the shitty hellfaurds car battery and it keeps getting flat every 4-5months. however its been my 3rd time that its happened now and ive got 3 years warrenty ...one years almost gone...i spoke to the manager i told him this is too much hassle coming here every 5 months to replace a battery and normally they supose to last up to 4-5years not 4-5 months and i asked him for a refund and he said he cant do that fcking pised off !!

managed to get a new battery from them idiots and now the cars idling at rest is fine but when im driving and i put the clutch down to for long and almost brake or either change a gear it drops quite low to say 400 rmps then hits back up to 700rmp. feels like as if it wants to cut out.

also the inspection light is on aswell loool.
it never used to do that before...whats the solution for it ?

thanks.

Post Sat Aug 22, 2009 7:22 pm

It will more than likely just sort itself out after a short while. The ECU will need to 're-learn' it's settings having been disconnected from the battery.

With regard to the inspection light, it may just be a coincidence that it came on now. You can re-set it by bridging two pins on the loom in the engine bay. I don't know which pins off hand but search on here or google and you'll find it...

Post Sat Aug 22, 2009 7:29 pm

I had a similar problem as you and it was the mounting bracket on the alternator was corroded and not earthing it to the engine properly.
Easy test to do is use a circuit tester set on resistance put one probe on the body of the alternator and one on battery neg, there should be no resistance between the two. Not the prefect test but could give you an indication that there is a problem. Its quite a common fault on e30s

Post Sat Aug 22, 2009 7:51 pm

johnl320 wrote:I had a similar problem as you and it was the mounting bracket on the alternator was corroded and not earthing it to the engine properly.
Easy test to do is use a circuit tester set on resistance put one probe on the body of the alternator and one on battery neg, there should be no resistance between the two. Not the prefect test but could give you an indication that there is a problem. Its quite a common fault on e30s

hmm i could try that way mind u i have been getting alot of alternator whine from my car speakers maybe to do with that.

so on the reading i should get 0 ohms. if there is ohms reading then what shall i do change alternator or just alternator mounting bracket ???

thanks.

Post Sat Aug 22, 2009 7:57 pm

Yep no Ohms (or very close to)

Take the alternator off and clean the mount where it touches the block etc, basically all metal to metal contact areas. Also check your engine to chassis earth while you are there.

Post Sat Aug 22, 2009 8:02 pm

sweet will do mate...cheers for that. im going to replace the alternator belt soo will check that in the process.

thanks.

Post Sun Aug 23, 2009 12:05 am

will lithium/vasline type grease work fine instead of copper based grease ?

Post Sun Aug 23, 2009 12:08 am

This should sort the service lights out.

http://www.noren.com/bmw/e30reset.htm