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Title: Battery Light staying on Post by: Crazypierre on September 30, 2011, 06:47:34 PM Hi Guys
Wondering if you could help me diagnose what's wrong? Few weeks ago dash battery light would flicker on just after start up but then turn off after a minute or two. Now, it stays on all the time... I put a voltmeter on the battery it while engine's running and it reads about 14.5 Volts at tick over. Does this mean the alternator is charing? What's the story? Cheers Pete Title: Re: Battery Light staying on Post by: Thotos on September 30, 2011, 07:01:51 PM If with the engine off your voltmeter reads 12V and with the engine running it reads 14.5V then the battery is charging. Rev the engine to about 4000 rpm and make sure the voltage doesn't go up to 17V :o If it stays at 14.5V then the problem is either faulty wiring or faulty regulator. If you have a Marelli alternator it's quite common for the triodes to go wrong and keep the light on. If the voltage goes high (17V+) when revving the engine then the regulator is faulty.
Title: Re: Battery Light staying on Post by: david on September 30, 2011, 09:08:21 PM I had this on my 131 sport a few years ago when I started it up one day so I removed the rear splash cover on the alternator and removed the two screws which hold the brush block/regulator in place, the fault turned out to be one of the brushes that had worn down with age.
Went in the shed removed the brush block /regulator from a spare alternator and problem was solved and you don't have to remove the alternator from the car, takes about twenty minutes (or less). Mine has a bosch but marelli are same idea and the problem is nearly always this or the regulator that is faulty but its all in the same part. Title: Re: Battery Light staying on Post by: david on September 30, 2011, 09:24:21 PM The part looks like this.......
Title: Re: Battery Light staying on Post by: Crazypierre on October 01, 2011, 06:54:03 AM Thanks Thotos and David,
David The car's only done about 20,000 miles from new. Would the brushes have worn after such a short time of use? Also, where can I get such a part? Thanks Peter Title: Re: Battery Light staying on Post by: david on October 01, 2011, 08:58:43 AM Well it wouldn't have worn if that is the corrext mileage but one of the brushes might have broken as I have seen this where they have snapped off.
Best bet is to remove it and have a look as I said its easy to do. Is your alternator Bosch or Marelli ? I once had a Thema turbo and the regulator bit of this part went wrong, this was a larger alternator and I think it was either a 90 amp or 110 amp alternator as the Thema had electric everything and air con etc but all I had was an old 131 45amp brush block/regulator that would fit in so fitted it and the alternator worked fine and never had another problem even I thought it might be to low ampage for the size of alternator but it was fine ! I may have some Marelli ones left but think I am out of Bosch ones. These can be bought but I think you need to look on Ebay USA or simular. Title: Re: Battery Light staying on Post by: david on October 01, 2011, 09:05:46 AM Yes they are on Ebay USA.
Type in bosch regulator and they come up as above but check they look same as yours and get the dimensions and ampage off the seller to double check but remove yours first and check it, They do marelli ones too. Title: Re: Battery Light staying on Post by: Thotos on October 01, 2011, 12:19:20 PM If the brushes are worn or broken, the alternator will not be charging the battery. If there's 12V with engine off rising to 14.5V with engine on then the battery is charging so the problem is not the brushes. But it could well be the regulator ('brush holder') shown above if the alternator is Bosch. Marelli alternators have separate brush holders and regulators and they also have a separate triode that controls the charging light. Bosch alternators have everything (except for the rectifier diodes) built into the regulator shown above so if you have a Bosch alternator then you might as well change that regulator. Go into any motor factors and ask for a regulator for a 1980(-ish) 3 series BMW.
Title: Re: Battery Light staying on Post by: david on October 01, 2011, 04:59:15 PM Well I had this self same problem on 131 sport and it was still charging 14.5 volts and the charge light was flickering and the fault was one of the brushes that had worn and the problem was rectified so whats the pronlem in checking it out as it is a quick and easy thing to do.
Title: Re: Battery Light staying on Post by: Thotos on October 01, 2011, 07:35:15 PM ??? But I agreed with you David and said:
you might as well change that regulator Title: Re: Battery Light staying on Post by: jseabolt on October 02, 2011, 11:24:22 PM Thanks Thotos and David, David The car's only done about 20,000 miles from new. Would the brushes have worn after such a short time of use? Also, where can I get such a part? Thanks Peter Those units are made in China and the one I had on my Yugo lasted about 1000 miles before it died. The next step up is WELLS which is made in Mexico. Title: Re: Battery Light staying on Post by: jseabolt on October 02, 2011, 11:34:05 PM Hi Guys Wondering if you could help me diagnose what's wrong? Few weeks ago dash battery light would flicker on just after start up but then turn off after a minute or two. Now, it stays on all the time... I put a voltmeter on the battery it while engine's running and it reads about 14.5 Volts at tick over. Does this mean the alternator is charing? 14.5 means the alternator is trying to charge a weak battery. I have actually never seen a Bosch or Iskra (Slovenian made Bosch copy) alternator produce more than 14.3 volts but that could just be inaccuracies between multimeters. If it reads something like 13.8 volts, that usually means the battery is in good shape and the alternator is not having to work. I know that sounds odd but that's what a guy I work with who used to make batteries at the Exide plant in Bristol (Tennessee that is) told me. Try it. Drive the car around for awhile and see if the voltage does not drop off to below 14 volts. I was trying to diagnose a starting issue with my 124 Spider. Turned out the starter was at fault not the battery or alternator. Also if your light is burning yet the alternator is producing 14.5 volts, I would suspect a the diode in the dash indicator circuit is going bad. The light on my 124 Spider has always stayed lit to some extent when the headlamps are on. What's the story? Cheers Pete Title: Re: Battery Light staying on Post by: Tas131 on October 03, 2011, 09:08:24 PM I've just bought one of these, it's currently in the post.
http://www.ebay.com.au/itm/360272904936?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 Google the part number on the regulator you have, bosch always has hundreds of numbers for the same item. Make sure you get the one for 28mm slip rings, they make one for 32mm that looks the same. Title: Re: Battery Light staying on Post by: david on October 04, 2011, 07:29:55 AM Thats the problem now a lot of the manufacture of these parts is subbed out and the quality suffers.
I have a complete lucas alternator in the shed if your interested, it was off a 1600 CL mk3(single cam) but as I have never had a pushrod engined 131 I don't Know if the alternator is on the same side ? is it?? |