LoudBimmer Posted November 10, 2012 Report Share Posted November 10, 2012 I have a huge problem with alternator and voltage in my bmw e46 325i. Little back ground about the problem: I put a little system a while back. First amplifier was 1200watts and alternator was keeping up with it. I also upgraded my battery to kinetik hc1800 so everything was going good. After few months I upgraded amplfiier to 2500watts (it pulls ~250amps) and the battery to xs power D3100. One day after picking up my car from good year (took it for suspension check) my voltage was pretty low, ~13.5-13.7v. But eventually it went back up to 14v. So I decided to upgrade my alternator to a high output(singer alternator), 260A. When I pulled the original alternator out, it was locked, wasn't turning at all. When I put the 260A in, the voltage was around 13.8v at idle and 14v at 2k rpm. BUT, when I put a load on it, like rolling windows up, the voltage would drop down to ~13v and climb back up. So I thought that the alternator was no good and sent it back to the Mike who tested it and it came out to be perfectly fine. So I ordered another stock alternator which does the same exact thing. As soon as I apply load in it, voltage goes down. Like if I shift the gear into "rear" voltage drops down little bit and climb back up. I talked to Mike who built HO alternator and he said that it's because of the belt slip. But how can I have belt slip with stock alternator? What could the problem possibly be? I've checked all connections, charged battery and bought a new belt from dealership. I'm thinking maybe a relay somewhere went bad because of the stock alternator not working properly? I had a topic about this before, but I can't find it. Other thing I've done is pulled the terminals off battery with car on, and the car was still working with voltage around 13.5, when rolling windows up it dips down to ~9v. Unplugged the plug from alternator and turned the car on and same exact problem still there. Link to comment Share on other sites More sharing options...
fox_racin4 Posted November 10, 2012 Report Share Posted November 10, 2012 Im going with a bad battery. A battery can float at 12.7v But still be bad. Try another battery or check over all conections 1998 gmc extd cab 12 crossfire C710s 4 SAZ-4500s 3 Singer 400A altsbuncha mids/highs Team Asshole Link to comment Share on other sites More sharing options...
LoudBimmer Posted November 10, 2012 Author Report Share Posted November 10, 2012 Tried it with 2 different batteries. Kinetik and xs power, both charged. Link to comment Share on other sites More sharing options...
fox_racin4 Posted November 11, 2012 Report Share Posted November 11, 2012 Stock wire from alt to trunk?? (IIRC bmw batts are in the rear) 1998 gmc extd cab 12 crossfire C710s 4 SAZ-4500s 3 Singer 400A altsbuncha mids/highs Team Asshole Link to comment Share on other sites More sharing options...
LoudBimmer Posted November 11, 2012 Author Report Share Posted November 11, 2012 I have 1 run of 0 gauge, but with stock alternator I just use stock 2 gauge wiring. Link to comment Share on other sites More sharing options...
Tarball Posted November 11, 2012 Report Share Posted November 11, 2012 Put a charger on your battery. Check if you need a new belt, if your belt is loose alt wont turn properly. Big 3 in 1/0 - as mentioned above - did you do a complete big 3? Yes that includes a long run of 1/0 with 2 fuses (1 near alt, 1 near bat) to the back if your bat is in the rear. CURRENT SYSTEM: Alternator: Stock alt on mids/highs Isolated DC Power 270 SP - Charging @ 16.8v Batteries: (2) XS D1400s Power Cable: Double Runs of 1/0 KNU Kolossus Fleks Headunit: 80-PRS Sub Amp: DC 5.0k Subwoofers: 2 RE MT 15s /PSI dual .7ohm recones Subwoofer Enclosure: 9.1cubes @ 32hz - brutal. Mids & Highs Amp: CT125.4 Active Components: Mids RE XXX 6.5c Highs - 3 RE XXX tweeters per side(A pillar) Noise Control: Damplifier Pro all over the cab. Build Log If you do business with me please leave feedback here: FEEDBACK THREAD Highest Legal Score: 151.0 db Highest Musical 30 Second Average: 151.6 db Link to comment Share on other sites More sharing options...
LoudBimmer Posted November 11, 2012 Author Report Share Posted November 11, 2012 my guess would be that there is something wrong with belt tension or belt grip, since as soon as load is applied, voltage dips down. Or possibly a relay might of went bad, but since I unplugged the plug that goes to alternator, same thing is still happening. Link to comment Share on other sites More sharing options...
fox_racin4 Posted November 11, 2012 Report Share Posted November 11, 2012 you MAY not even need that plug for the alt to turn on, depending on what regulator the alt is using, i know i dont need to plug in my plugs into alts for them to "turn on" 1998 gmc extd cab 12 crossfire C710s 4 SAZ-4500s 3 Singer 400A altsbuncha mids/highs Team Asshole Link to comment Share on other sites More sharing options...
LoudBimmer Posted November 11, 2012 Author Report Share Posted November 11, 2012 Here's a quick video about the problem. Link to comment Share on other sites More sharing options...
Tarball Posted November 13, 2012 Report Share Posted November 13, 2012 Question, did you replacement H.O. alternator have a smaller pully than the stock ? CURRENT SYSTEM: Alternator: Stock alt on mids/highs Isolated DC Power 270 SP - Charging @ 16.8v Batteries: (2) XS D1400s Power Cable: Double Runs of 1/0 KNU Kolossus Fleks Headunit: 80-PRS Sub Amp: DC 5.0k Subwoofers: 2 RE MT 15s /PSI dual .7ohm recones Subwoofer Enclosure: 9.1cubes @ 32hz - brutal. Mids & Highs Amp: CT125.4 Active Components: Mids RE XXX 6.5c Highs - 3 RE XXX tweeters per side(A pillar) Noise Control: Damplifier Pro all over the cab. Build Log If you do business with me please leave feedback here: FEEDBACK THREAD Highest Legal Score: 151.0 db Highest Musical 30 Second Average: 151.6 db Link to comment Share on other sites More sharing options...
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