alternator wont charge battery

Ok my brother came by to take another look and heres what happend: he put a bolt he said was missing frm the alternator on we think its to ground it. He checked continuity from alternator to battery and fuse box... Everything was good. And I think it may have been the bolt cuz we checked voltage the whole time n after that we got up to 13.3 volts... BUT the car doesnt charge when being idled... With the car on it now charges but not driving so now what should we check? He even brought another white wire from a diff. Honda n it was doin the same as mine so mines good...

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Originally Posted by lexanbobby

Ok my brother came by to take another look and heres what happend: he put a bolt he said was missing frm the alternator on we think its to ground it. He checked continuity from alternator to battery and fuse box... Everything was good. And I think it may have been the bolt cuz we checked voltage the whole time n after that we got up to 13.3 volts... BUT the car doesnt charge when being idled... With the car on it now charges but not driving so now what should we check? He even brought another white wire from a diff. Honda n it was doin the same as mine so mines good...

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the alternator doesn't ground through a bolt, it grounds through the engine block it's bolted to. check the ground straps from the body to the engine

x2. check the grounds.... and get rid of the f...ground battery cable and install something better (I used a 4G ground wire there.... longer but way way thicker)

the heavy white wire goes directly to battery
white/green goes to fuse 8 in the under hood fuse box,and should be hot all the time

black/yellow should be hot with the key on, it goes to fuse 1 and the inside fuse box.

white/blue goes to the charge warning light

on the FI cars white/red goes to the ecu

I can't remember exactly how the ecu reduces charging voltage, but I know the alternator will function with the white/red disconnected, I believe the ecu sends a ground signal to the regulator to reduce charge current when not needed, this improves fuel economy. you could check all the other connections then disconnect the white/red to see if it charges at idle. It could possibly be the ecu thinking the car doesn't need to charge.

is it only giving that 13.3 volts when you give the car a rev, but just back to battery voltage when idling?
to me that sounds like the rectifier has a diode out or the brushes are fucked.

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Originally Posted by Hauntd ca3

is it only giving that 13.3 volts when you give the car a rev, but just back to battery voltage when idling?
to me that sounds like the rectifier has a diode out or the brushes are fucked.

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well the alternator light stays on even with the alternator unplugged and goes out when you unplug the choke, there should be enough resistance in the choke heater coil to keep the light from coming on by it grounding through the coil. I'm sending him a good choke coil out of my junk, since the alternator changes the status of the blue/white wire to positive when charging, to turn off the charge warning light and power the choke, it seems that that voltage is finding it's way right to ground through the choke coil

I think I said it wrong it charges at idle but not when getting gas.... When we rev it the charge drops way down.

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Originally Posted by lexanbobby

Ok I checked out the wires goin from alternator it goes under the battery to the fuse box and the part that goes under the battery is kinda jacked up... Its showing the white wire and yellow and green wire. On the yellow n green it has a spoy showing acttual wires inside. Soo do I tape it up or do I gotta replace it? I know those r causing problems cuz when I messed with them the car got a couple more points of voltage... Am I on the right teack?

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Have you fixed this problem yet or are you still trying to charge with exposed wires that are likely grounding out on things?

Sorry people mived a couple times and had no phone to log on with... Welll still having the issues. Car no longer charges while on at all. Battery starting to take forever to charge- got a hone charger to help till we get the funds to fix it... Dash lights not lighting up, tail lights have gone out, more than half of the fuses in under dash fuse box dont light up- but have been checked and r good, did replace a few to c if it helps, oh and speedometer acting up...works when it wants to basically, and drivers front power window wont roll up anymore, and off the subject- motor mount keeps losing a bolt...so theres a fun update for eveyone lol

PM me

The gods are angry with you. :(

Am experiencing the same exact problem- so far I ruled out the alternator being bad and the battery- (they are brand new) I did a continuity test by disconnecting the battery negative cable and connecting an old school volt meter - lit up like a Christmas tree! I started pulling fuses one by one (engine bay main fuse box) - I was getting constant power through the negative battery cable to my battery - when I pulled the clock fuse the voltmeter light immediately turned off! That didn't fix the problem when I pulled it but its a starting point to diagnosing the issue. Hopefully I can solve this issue but it's most differently a ground issue and some sort of breakage somewhere in the charging system :( if anyone can help! Chime in please!


New Battery not charging / alternator not reading 14v - ground issue ? Wiring issue? All the symtoms of a bad alternator but simply not the case -:(

Ok- I found out my issue - bad new factory parts! replaced the alternator for a third time and BAME! Power to the alternator ! - I did some serious testing to be sure that my wiring harnesses from the voltage regulator wasn't the culprite / I have some suggestions for the individual still struggling with the no charge alternator issue - test all ports at the voltage regulator harness plug for power on all four wires /be sure your car is in start mode (key in ignition turned /not started) you should have power from all four connections/ voltage reading should be in the 12.0 range for three of the four connections and one should read about 4.57 or 5.0 (that's the wire to the ecu) if you aren't getting power through anyone of those connections--you can bet it's a broken wire or bad connection - otherwise -test your new parts to be sure they aren't faulty :) hope this helps

Replace your starter what happened to mind my starter worked fine had it tested tested fine was losing power to my starter

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Originally Posted by deathblood6

Ok- I found out my issue - bad new factory parts! replaced the alternator for a third time and BAME! Power to the alternator ! - I did some serious testing to be sure that my wiring harnesses from the voltage regulator wasn't the culprite / I have some suggestions for the individual still struggling with the no charge alternator issue - test all ports at the voltage regulator harness plug for power on all four wires /be sure your car is in start mode (key in ignition turned /not started) you should have power from all four connections/ voltage reading should be in the 12.0 range for three of the four connections and one should read about 4.57 or 5.0 (that's the wire to the ecu) if you aren't getting power through anyone of those connections--you can bet it's a broken wire or bad connection - otherwise -test your new parts to be sure they aren't faulty :) hope this helps

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So I tested the connections like you said and found that one wire is not getting voltage. It's the white/green wire which is the one going to fuse no. 8, as I understand it, which is for the voltage regulator. Any suggestions on how to replace that wire?

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Originally Posted by mikeharriswho

So I tested the connections like you said and found that one wire is not getting voltage. It's the white/green wire which is the one going to fuse no. 8, as I understand it, which is for the voltage regulator. Any suggestions on how to replace that wire?

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But the fuse is good correct?

The fuse was good. So here's an update. I replaced the wire going from the voltage regulator to fuse no 8. I'm getting a charge but I'm only getting 11v

If you look in to book there is a way to make the alt go full field for a test. I am not sure how to do it. And make sure your alt is for a fuel injected car.

Good chance the alt is just bad.

Thanks for the info. The alternator was definitely for the fuel injected car. Here's the update: Ive gone through 5 alternators, all of them remanufactured. I have tested all the contacts in the 4 pin connector and all of them are receiving voltage from the battery. I took the car to an automotive electrician. He said everything is fine but the alternator. I was told that I need to buy a Denso alternator for the car but cant seem to find a new one. They are all remanufactured. I will have to take a chance at it and buy a reman Denso alternator I guess. Any input guys?

I'd take a flier on a reman Denso. I wouldn't on a non-OEM rebuilder though.

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Originally Posted by Dr_Snooz

I'd take a flier on a reman Denso. I wouldn't on a non-OEM rebuilder though.

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I ordered it. Hope it works. I'll keep you updated!

So I got the denso today, installed it. Still same issue. Only charging at 12v. Can't figure out what the problem is...

What is the resistance in the white wire that goes from the alternator to the underhood fuse block? Check that all very carefully. Look for damage to the wire, corrosion on the connectors, melted plastic, etc. Better yet, take all the connections apart, wire brush, then coat with silicone grease and re-assemble.

Are you having any other electrical issues?

Edit: also check your engine grounds.

More edit: how old/sulfated is your battery?

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Originally Posted by mikeharriswho

So I got the denso today, installed it. Still same issue. Only charging at 12v. Can't figure out what the problem is...

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have your electrical buddy check that alt again or better yet have him rebuild it so you know it works.

Revving it to 2000 rpms you get the same 12v? They wont charge much at idle sometimes.

I don't see the white wire going to the fuse block. I'm not having any electrical issues. The battery is new and the engine grounds are good.