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Druman
Joined: 19 Mar 2007
Posts: 419
Location: Middleport, Ohio
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 Posted: Thu Jul 17, 2008 3:35 pm Post subject: Battery light stays on till 2300 RPM |
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Ok here's the story: My old alternator went out on me so I had a shop replace it with a brand new one, well when I got the car back I noticed that the battery light stays on until I hit 2300 RPM. I'm not sure if it's something with the alternator itself or if it's a connection somewhere. Anyone have any ideas?
TIA
7osh
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87' 924S non-sunroof (Red) 45K miles
85' 944 "early" NA (Red) 130K miles
PORSCHE pisses excellence... |
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vexed73
Joined: 05 Oct 2007
Posts: 187
Location: EASTERN, nc.
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| Posted: Thu Jul 17, 2008 9:21 pm Post subject: |
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Is the belt tight? Other than that I am useless.
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1982 PORSCHE 931 |
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Rich H
Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK
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| Posted: Thu Jul 17, 2008 10:53 pm Post subject: |
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Smaller pulley would sort it.
Could be the reg on its way out or a goosed alt..
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Fri Jul 18, 2008 1:19 am Post subject: |
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Stop by FLAPS for a free charging test. You may have gotten a bum unit.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Fri Jul 18, 2008 4:25 am Post subject: |
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Yeah, they're supposed to go into charge mode with a 12v+ "signal" from the exciter wire (the same wire that the dash light is on). We can assume the exciter wire is good (and properly attached at both ends) because the light comes on when the ignition is switched on...and it does eventually shut off. -So it's looking most like an alternator problem.
They can and will start charging at a higher rpm as you found, but should start charging at a much lower rpm with the 12v+ from the exciter wire.
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"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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ideola
Joined: 01 Oct 2004
Posts: 15550
Location: Spring Lake MI
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| Posted: Fri Jul 18, 2008 4:34 am Post subject: |
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| Rasta Monsta wrote: | | Stop by FLAPS for a free charging test. You may have gotten a bum unit. |
I got three bum units the last time I replaced the alt on my 924S. I also got three bum units the last time I replaced the alt on the 924. Such a royal PITA. Takes three tries, crawling on your back in cold wet snow to replace an alt that's supposed to be remanufactured & tested. Sometimes, lifetime warranties just don't cut it. But at least I didn't have to pay for the part three times apiece. Moral to the story, suspect the alternator. Take it in and make sure you get a FULL test, not just a voltage output test. The Murray's near me has three tests they run (don't remember what they're each called), and every time I would get a pass-pass-fail.
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Fri Jul 18, 2008 5:15 am Post subject: |
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Autozone and Advance Auto (Partsamerica) do free alt tests too.
This one's an Autozone test of my Jeeps' Delco alt. They test "lamp/diode trio", "regulator", and "rectifier".
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"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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John_AZ
Joined: 25 Jun 2008
Posts: 130
Location: Arizona ~Carefree Highway~
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| Posted: Fri Jul 18, 2008 10:21 am Post subject: Re: Battery light stays on till 2300 RPM |
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| Druman wrote: | Ok here's the story: My old alternator went out on me so I had a shop replace it with a brand new one, well when I got the car back I noticed that the battery light stays on until I hit 2300 RPM.Any ideas?
TIA
7osh |
If you had a shop replace it with a brand new one, they should be responsible. Also, it may not have been the alternator in the first place.
John_AZ
1988 924S + 1987 924S |
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Druman
Joined: 19 Mar 2007
Posts: 419
Location: Middleport, Ohio
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| Posted: Fri Jul 18, 2008 2:06 pm Post subject: Re: Battery light stays on till 2300 RPM |
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| John_AZ wrote: | | Druman wrote: | Ok here's the story: My old alternator went out on me so I had a shop replace it with a brand new one, well when I got the car back I noticed that the battery light stays on until I hit 2300 RPM.Any ideas?
TIA
7osh |
If you had a shop replace it with a brand new one, they should be responsible. Also, it may not have been the alternator in the first place.
John_AZ
1988 924S + 1987 924S |
Well, I'm pretty sure the old alternator was faulty because it just stopped charging all together, I even had it tested, and once it was replaced it charged, but it just has that problem with the 2300 RPMs.
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87' 924S non-sunroof (Red) 45K miles
85' 944 "early" NA (Red) 130K miles
PORSCHE pisses excellence... |
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924guy
Joined: 29 Dec 2003
Posts: 2088
Location: Port St. Lucie, FL
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| Posted: Fri Jul 18, 2008 10:32 pm Post subject: |
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slightly o/t, but im thinking its probably a good idea to have the parts store bench test the brand new alternator before even leaving the store with it, given the apparent failure rate...
as for this topic, is it possible the diode in the alt is improperly rated? or it could be faulty and "leaking" for lack of a better word before my morning coffee, until it heats up...
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Eric
78 924
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http://www.cardomain.com/id/924Guy
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Druman
Joined: 19 Mar 2007
Posts: 419
Location: Middleport, Ohio
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| Posted: Sun Jul 20, 2008 4:19 am Post subject: |
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Ok here's what I've discovered so far: I hooked my meter to the battery and started the car, before the car was on I got about 12V after the car started still 12V once I gave it some gas it went up to almost 14V So it's not charging until 2300 obviously, (i think we all assumed that) Well, the pulley on the alternator does turn so I know it's not stuck, but when I hit 2300 RPMs I feel the car catch as if something is holding it back, strange eh? What would make it do that? I'm confused because if feels like the alternator is just kicking in and adding a little drag to the belt, but how could it do that if it's already moving?
Just lemme know if you guys have any reason behind this mystery 
7osh
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87' 924S non-sunroof (Red) 45K miles
85' 944 "early" NA (Red) 130K miles
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Smoothie
Joined: 01 Jan 2003
Posts: 8032
Location: DE (the one near MD, PA, NJ)
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| Posted: Sun Jul 20, 2008 6:04 am Post subject: |
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That little extra drag when the alternator starts charging is normal.
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"..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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Druman
Joined: 19 Mar 2007
Posts: 419
Location: Middleport, Ohio
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| Posted: Sun Jul 20, 2008 7:57 am Post subject: |
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So maybe the diode is not activating soon enough? I would think that it would be rated correctly being it was made for this car, again, I would "think", but you never know with these things.
7osh
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87' 924S non-sunroof (Red) 45K miles
85' 944 "early" NA (Red) 130K miles
PORSCHE pisses excellence... |
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