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Registered
Join Date: Mar 2003
Posts: 27
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Alternator or regulator?
So I have finally been able to drive my 68 911 after an engine swap (73 2.4t) and I have discovered that the car is not charging properly. . I just put a new battery in in two weeks ago and it is now dead, the headlights were dim, slow turn signal, etc. .
My question is. How do you determine whether the issue is with the voltage regulator or alternator? Also, is there an easy way to tell the difference between a Bosch or Motorola alternator on a 73.t? Thanks, Alan Arringto 1968 911 2.4t |
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09-01-2003, 10:14 PM
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Join Date: Sep 2002
Posts: 3,580
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Well, when you start the car, voltage at the battery should rise from 12V to about 14.2 or so. This usually indicates that the alternator is OK. If too high, the voltage regulator is usually the culprit, and if too low, I'd look into the alternator being bad. With slow signals and dim lights, voltage is probably low.
Why did you replace the battery two weeks ago? Somtimes we replace a "bad" battery, only to have the new one go bad also, because it has been overcharged because of a bad V.R. Are any sulphur smells or flickering lights present? Sorry I can't help with identifying the alt. brand, other than to say you can always pop it out from the fan housing and take a look at it.
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993 Last edited by cowtown; 09-03-2003 at 10:36 AM.. |
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09-03-2003, 10:17 AM
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Join Date: Jan 2002
Location: VA
Posts: 591
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When changing engines on early cars (pre SCs) remember that the old style alternators had separate regulators. Replacement alternators have had the regulators built in for years, so there was a minor rewire needed when R & Ring the alternator. Make sure your new motor’s alternator/regulator & old alternator/regulator are in sync.
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09-03-2003, 11:36 AM
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Join Date: Dec 1999
Location: TX USA
Posts: 9,804
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Alan,
I hate to say this, but ... If you don't know what brand your alternator is, how do you know the regulator is the same brand??? On 2,7 and earlier engines ... Bosch alternators had 14 mm shaft threads, and Marchal/Motorola alternators had 16 mm shaft threads. Mixed brands of alternators and regulators DO NOT WORK!!! Resolve the brand issue, and be prepared to do some additional troubleshooting with a digital multimeter ...
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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09-03-2003, 01:07 PM
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Join Date: Mar 2003
Posts: 27
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I had read in a post a while ago that the Marchal/Motorola had the larger shaft out of the two. The 68 2.0 motor that came out of the car had a smaller shaft so I assumed the larger shaft on the 73 meant Motorola. Based on that I purchased a voltage regulator for the Motorola/Marchal. .
Anyway I used a multimeter to test the red leads from the alternator. They seem to be fluctuating between 9-16. I guess this means that I am not getting an accurate reading? I have a wiring question in regards to the alternator. Here is how I have the wires currenty assigned, is this correct? The 73 has the following wires from the alternator: Thick Red - - - (goes to the starter) is currently hooked up the same post on the starter with the lead from the battery. Red - - -runs accesories (I currently do not have this going to anything since the 68 did not have many accesories (not using rear heater relay) Black- - - currently hooked up the voltage regulator Brown - - - currently hooked up to a body ground. (is this correct??) Blue- hooked up to voltage regulator D+61. Blue from vr to idot light. Fuel Pump is using a battery lead, car has webers. Does this seem correct? If so, I may be looking at a new alternator right? Any help is greatly appreciated. Thanks, Alan ----------------------------------------------------- Arringto 68 911 Targa 2.4t |
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09-07-2003, 06:23 PM
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