Bad alternator?

xenocron · Post by **xenocron** » Wed Jun 11, 2008 9:39 pm

Anyone know if there is one of these \"B+\" wires on the H Alternators? I am having similar issues where the car will start and run fine for a bit, around 13.8 - 14 volts...as it warms, voltage drops into the 12s. I am think that is it...

james25 · Post by **james25** » Fri Jun 13, 2008 8:58 pm

H engines should also have the B+ wire on the alt, its a thick wire and its bolted to the B+ terminal on the back of the alt. Well I'm still back at square one, I took the alternator off and had autozone test it and its good. I cleaned the alt bracket that bolts to the block, cleaned my grounds again. I also took a piece of ground wire and hooked it up to the negative terminal of the batt and hooked the other end on the alt housing. Still no go.

JaredKaragen · Post by **JaredKaragen** » Fri Jun 13, 2008 10:26 pm

is it a nippendenso alt? I have had many do this to me; but it would fluctuate between 14.2 and 12.25. Mitsubishi ALT's like to run right from what I have seen. I would check the regulator in the ALT; that's normally the first thing affected by heat; that and the diode array.... Bad reg's in ALT's are common; but are heat induced.... so they \"test\" fine....

xenocron · Post by **xenocron** » Sat Jun 14, 2008 10:30 am

I think mine is heat related...and I think the ALT is shot. I need to pull out the Manifold and Turbo and get them both coated...even the car runs way to hot, so I need to do something.

Adam Hopkins · Post by **Adam Hopkins** » Sat Jun 14, 2008 2:11 pm

I am seeing my car idle at about 14 when it first starts up then after driving a while at idle it only wants to charge 12.5 to 13. as soon as a rev over 2000 it charges correctly. I think it might be heat related also.

xenocron · Post by **xenocron** » Sat Jun 14, 2008 3:39 pm

Adam Hopkins wrote:I am seeing my car idle at about 14 when it first starts up then after driving a while at idle it only wants to charge 12.5 to 13. as soon as a rev over 2000 it charges correctly. I think it might be heat related also.

mine will hit 13.5-14.0 rarely after its heated up...even revving out to 5k

greasemonkee · Post by **greasemonkee** » Sat Jun 14, 2008 6:25 pm

Adam Hopkins wrote:I am seeing my car idle at about 14 when it first starts up then after driving a while at idle it only wants to charge 12.5 to 13. as soon as a rev over 2000 it charges correctly. I think it might be heat related also.

These were my symptoms... Haven't tested yet with the new alt.

JaredKaragen · Post by **JaredKaragen** » Sun Jun 15, 2008 12:53 am

Adam Hopkins wrote:I am seeing my car idle at about 14 when it first starts up then after driving a while at idle it only wants to charge 12.5 to 13. as soon as a rev over 2000 it charges correctly. I think it might be heat related also.

That is a failing regulator symptom..... When regs get hot they used to lock on full blast... a common problem on older motorbikes.... Same design, just smaller, so the reg deals with more heat. To fix the problem with cooking batteries, they redesigned regulators to do the reverse, put out less... the problem with heat is it gives inconsistent results so it's better to slightly undercharge than overcharge (Voltage wise and for your battery's sake).

james25 · Post by **james25** » Sun Jun 15, 2008 7:50 am

JaredKaragen wrote:is it a nippendenso alt? I have had many do this to me; but it would fluctuate between 14.2 and 12.25. Mitsubishi ALT's like to run right from what I have seen. I would check the regulator in the ALT; that's normally the first thing affected by heat; that and the diode array.... Bad reg's in ALT's are common; but are heat induced.... so they "test" fine....

Mines a mitsubishi alt, I have another used mitsu alt that I keep for a spare. I'll just swap out alts. Is it possible the ELD is all behind this? My symptoms are heat related, my car ran perfect last winter...no voltage drop from charging system.

Post by **calvin** » Sun Jun 15, 2008 1:36 pm

you might want to contact Kelly(here or NepTune forum) he did plenty testing ELD/Alt Control/Alt etc etc

Adam Hopkins · Post by **Adam Hopkins** » Sun Jun 15, 2008 3:08 pm

Its definitely worth looking into. It is not a huge problem it just makes your tune much more sensitive to battery tables. The more constants we have in the equation the easier it is to control.

james25 · Post by **james25** » Tue Jun 24, 2008 5:46 pm

Well I swapped the alternator and still does it. I did find out that when I have my headlights on at idle even if its hot outside or the car is hot, the charging voltage is at 13.8v and it just stays there which is good. I raised my idle to 850rpm to compensate for the idle drop that I'm having, before when the voltage drops to 12.5v, my idle would drop also. Now with no load at idle, it would drop down to 750rpm which is fine with me. My car doesn't like the 650rpm idle, it stalls. But like what Adam said, tuning becomes more sensitive.

Post by **calvin** » Tue Jun 24, 2008 6:04 pm

did u cut the alt control wire?

james25 · Post by **james25** » Tue Jun 24, 2008 6:36 pm

calvin wrote:did u cut the alt control wire?

Nope, I did not cut the altc wire. What would happen if I cut it?

Post by **calvin** » Tue Jun 24, 2008 6:55 pm

Disable in ectune alt control first. Then if that doesn't work cut the wire... Alt control lowers the charge voltage of the alternator. For example JDM/EDM cars don't have that... so they charge all the time high volt. USDM cars lower the charge voltage. i hope i said it correctly