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alternator charging problems
took the car out friday morning for a very short trip to local store - right before i turned it off i saw the warning lights come on but i was thinking that's just the car shutting down - when i came out it wouldn't start - seemed like the battery was dead...very slow turn of starter - called for help - tried it in the mean time and it caught and started - drove it home no problems but the voltage needle was at 0 - put the charger on the battery - took the alternator out looking for ??...loose connections or something - found a bad solder on the right joint in the picture - re-soldered both of them and re-installed the alternator - fired right up - drove it about 3 miles to test - a first it seemed ok then the volt meter went to 0 again - back home i disconnected the battery while it was running and the dash gauges changed their readings and the radio went off - a reading at the jump post showed 9.5 volts being put out by the alternator - so is the alternator bad or is it the regulator? - when alternator was out it looked good, spun smoothly, no burnt smell - are the regulators still available? - i have another alternator from a 79 - mounts are the same, pulleys are different - 85amp - would that work in the 84 - the 79 one has a different regulator setup - a picture of it is here also - thanks
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i see the regulators are available fairly cheaply - is it worth the try to get one and see? - is there a way to test just the regulator? - if i take it to autozone they will test it but since it's only putting out 9.5 volts i know they'll just say the alternator is shot
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84 928 S - SOLD 2012 Cayenne S Last edited by honerboys; 08-18-2019 at 02:20 PM.. |
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It sounds like the voltage regulator is going bad. Just replace it and see what the result is. Also, run the wire from the 14 pin connector to the alternator to make sure there isn't an issue in that circuit.
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Ed 85 928 5 spd (guards red over tan) 07 Shelby GT500 6 spd (torch red over two tone black and red leather) |
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Petie3rd
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warning dont disconnect the battery while the engine is running you can fry your computers.
This is not a valid test to see voltage output from the alternator. I would suggest that you only use name brand regulators for the alternator any cheaper version will usually lead to over charging issues. If you put a new regulator in and the charge will not be at 13.5 or higher at 1500 RPM then its quite possible one of the diodes has failed. If the charge goes to 14.7 or higher then your regulator has failed
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^^^ Stan ^^^ 2019 BMW K1250 GS 2016 HD RK 1988 S4 Auto , Elfenbein Perlglanz, Pearl Gray 1982 5sp Met black and tan sport seats |
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thanks ed and stan - i may have heard that before - but i probably forgot - something about resistance in the circuit - the removing the battery diagnostic is something old school from long ago - back before electronics - when i removed the battery the meter read 9.5 briefly - then dropped lower - then it stalled - started right up again with battery re-connected - so hopefully i didn't do any damage - i've got a new regulator - had a minor procedure done on my back so i can't lay on concrete but in a couple of days i'll report back on what occurred
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Aren't minor back surgeries those that are done on someone besides yourself? I hope you feel much better soon.
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) |
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Kyle C
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I had bad luck with alternators for my 1984. Ended up discovering that a Saab 900/9-3/9-5 alternator is almost exactly the same form factor as a stock 928 alternator, and they come in both 90A and 130A varieties. Current running a 90 amp version in my car, cost me $20 at the junkyard and so far has been much more reliable than the last three Bosch reman units I had run. Didn't require any modifications to install, but ideally you should shave a couple mm off the back of the mounting ears so that the belt will track 100% straight. Otherwise, just swap your pulley (my car using the 5-rib belt) and install. Same electrical connections as well. Let me know if you want more details and I can pull up part numbers. I think I have some photos as well.
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hey stepson - by minor i mean i had a growth removed - really simple until it got infected - just an open wound now - opelotus i would be interested in that setup - if the regulator doesn't fix this i'll be looking for a replacement - i do have that 79 alternator but it is only 85 amps - the 84 has more electrical equipment than a 79 so not sure if that's enough - a 130 amp that bolts right in would be ideal - can the saab unit accept the cooling duct? - if it does that would be the way to go
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got to this today and i'm happy to report the new regulator seems to have fixed the problem - at idle i have a little over 14 volts - turned on headlights (high beam), blower on high, a/c on and it still was putting out over 13.5 volts - all measured at the jump post - didn't help the cluster meter though - it still has a ridiculously low reading - maybe some day i'll get to that - when i last had the cluster apart i had to remove some of the pointers - so now the gas gauge never goes to full and the speedo is about 5 miles above actual speed - but i really hate going in there as everything is so delicate from age - sort of like it's owner - thanks to all who chimed in
cold idle ![]() high beams, blower, a/c on ![]() cluster ![]()
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Honer,
I believe there is an adjustment screw on the side of the volt meter to adjust the meter reading without removing the needle. But I hear you about removing the 30-40 year old instruments.
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) |
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Alternator Replacement -
Hey Honer - One other option you might consider if you have any further problems with your current alternator is to install a 1988 Camaro 2.8L Delco Remy CS-130. Do an informational alternator search on Pelican Parts and/or Rennlist.
Here is a write up on installing the CS-130 alternator using the original Bosch mounting/belt adj arms. 1983 928 Alternator With over 8 years of problems, failures, repairing, nursing, coddling, 2 new voltage regulators, smaller drive pulley diameter and 2 complete Bosch alternator replacements - after installing a Delco unit all my alternator failures and low out put charging problems were eliminated. Just returned from Colorado this week in 97 degree heat through the pan handle of Texas. A/C blower on full tilt both directions and my (added - lower shelf) digital voltmeter reading 13.7 volts. Good Luck Michael
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1984 928S - "Miss Purdy" 1987 911SC - "Frau Helga" 1986 930 - "Well Hung" 1975 911 Targa "Blue" Last edited by JK McDonald; 08-26-2019 at 02:15 PM.. |
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hey stepson - can that adjusting screw be accessed without pulling the pod out? - i had disassembled the gauge cluster years ago - did some soldering, bulb replacement, odometer gear, and since the gas gauge sender didn't work i replaced that also and tested it by pushing the float all the way to the top and moving the actual gauge needle to point to full - well evidently that float never goes that far up in the real world so now the needle only goes a little higher than 3/4 - as for the speedo.. i thought i had marked where it went back but that too didn't work out exactly as planned either - michael - i hear you on the alternator - if this doesn't stick as a fix i'll have to look at some other arrangement - that saab fix above might also be a possibility - i'm really glad this didn't happen 3 weeks ago when my wife and i were driving across nevada on the "lonliest highway" - that would have been VERY bad - hope your trip to colorado was fun -sorry about the road conditions - i think colorados roads are the worst
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Honer,
I think it's got to be removed to access that adjustment. https://rennlist.com/forums/928-forum/824844-dash-voltmeter-reads-low.html
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) Last edited by stepson; 08-26-2019 at 04:55 PM.. Reason: add link |
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drove the car last week and everything was fine - been really cold and snowy here so it sat for a week - drove it today and the dash meter was going over 14 volts..almost to the orange warning zone - when i got it home i put a meter on the jump post and it read the same thing as the dash meter - 15.1 volts with RPM's up around 2500 or so - so now it's over charging? - nothing changed in the week it sat..so? - weird how now the dash and jump post read the same now - dash meter was always all over the map but usually very low - could the regulator be crapping out already? - it's one of those HUCO units - are there better ones out there?
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Digital VM -
Hey Honerboy - Our 928 dash voltmeter is known for their unreliable readings. Have you considered installing a digital voltmeter from the jumper post to monitor the actual alternator output ?
By placing the digital VM within eye sight on the shelf by the drivers left knee, if (or when) the dash VM suddenly does something weird, you'll know immediately whether the alternator is acting up. Good Luck - Michael
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hey michael - i've known my dash meter was not to be trusted for a while - just don't want to open pod to fix (too lazy) - but until yesterday it never agreed with the actual voltage measured at jump post - don't think cold weather would effect it - it's in a garage so i wouldn't suspect water getting in to anything - i've always thought the regulator should not allow voltage over 14.5 or so volts - is this correct?
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Cheaper regulators will allow the alternator to overcharge the system-not good for computers.
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) |
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stepson - so what is a good regulator? - this alternator seems fine - no noises, smooth bearings so i really don't want to change it out with the chevy or saab replacement if i don't have to - i looked online and i seemed the huco was what was out there
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I have to find it but MrMerlin has posted about using cheaper on line regulators. He also had recommendations for which ones to use.
Coming clean: I also have this same problem with over-amping in the Stepson and need to change the regulator as well.
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) |
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Honerboys,
Looked up some previous recommendations. Opelotus has posted that Huco IS a good quality regulator. So......... I also found a previous thread that spoke of an adjustable regulator originally for a Volvo Here the thread: Alternator and Exciter Question I'm going to keep looking for all of us. ![]()
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John Curry (Drift King) 928OC member Grand Prix White 1994 GTS AT (The GTS) Black 1989 GT (The GT) and Cobalt Blue 1989 S4 AT (The Blue Car) 1986 Euro AT Indishrot 1984 Euro S AT (The Stepson) and Black Metallic 1984 Euro S 5 speed (The Schwartz) |
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