Alternator not charging at idle

[Drunner97]

Went through some deep water and now I'm having issues. Started out with the starter not really working. It would do a click, delay, then start. If the battery is charged though it seems to be okay. So I looked at the alt. Doesn't appear to be charging at idle. Replaced the alternator this morning. Still not charging at idle, but if I rev the engine, it will charge and shows 13-14v at 3k rpm. Drop down to idle and battery immediately starts discharging. Swapped batteries as well from my Tacoma. So ruled out bad battery. Any thoughts? Bad ground? Bad wiring connector?

 

[Drunner97]

On the advice of my uncle, I swapped the old alt back in and tried the Tacoma battery again. Same thing. Charges at 3k rpms but drains at idle. [MENTION=66389]BlackWorksInc[/MENTION] ?

 

[taxzz]

At this point I would replace the alt to battery lead. It's cheap enough to do and takes little time.

 

[Drunner97]

Hoping there's another solution before I start replacing cables.

 

[Drunner97]

Had the rebuilt alt tested and it came back good. Since I'm having the same symptoms with the rebuilt and the original I'm thinking I've ruled out the alt as the problem. Gotta be something shorting out somewhere. I'd say it's the batteries (plural because I put the Tacoma battery in) but unless both batteries are bad, that's unlikely the issue.

 

[BOSMECH]

Check and *CLEAN* all your grounding points especially your battery ground.

 

[liqourish]

check alternator fuse in the fuse box in the engine bay before you go on with other diagnostics

 

[Drunner97]

check alternator fuse in the fuse box in the engine bay before you go on with other diagnostics

Seems that if the fuse was blown, it wouldn't charge at all regardless of rpms, right? I'm going to buy a new battery tomorrow pending any other ideas from [MENTION=66389]BlackWorksInc[/MENTION] tonight.

 

[taxzz]

Seems that if the fuse was blown, it wouldn't charge at all regardless of rpms, right? I'm going to buy a new battery tomorrow pending any other ideas from [MENTION=66389]BlackWorksInc[/MENTION] tonight.

why would you buy a new battery if two tested okay? How long could it take to replace a cable?

 

[Drunner97]

why would you buy a new battery if two tested okay? How long could it take to replace a cable?

I haven't actually had the batteries tested yet. The battery from the Tacoma is only 4 years old with maybe 5k miles on it, I don't know the history from the 4runner battery. Same issue with both batteries though, so unless both are bad I really don't see that being the issue, but I'm running out of things to test.

 

[amalik]

I say wait for blackworks response.

I'm no mechanic, but to me -- your troubleshooting has already indicated the batteries are OK. If bad, I don't anticipate they would be able to charge at 3k revs as you mentioned.

I think you buying another battery is shooting blanks as you scramble in troubleshooting.

 

[BlackWorksInc]

I'd start by checking all your fuses, while the main Fusible Link might be okay, I am wondering if your 7.5Amp Alternator fuse may be blown. It sounds like the issue is that the alternator isn't being commanded to charge effectively.

 

[Oneluv13T4R]

This all sounds so familiar like I've heard someone tell you all of this already today...mmmmm.

 

[Drunner97]

I'd start by checking all your fuses, while the main Fusible Link might be okay, I am wondering if your 7.5Amp Alternator fuse may be blown. It sounds like the issue is that the alternator isn't being commanded to charge effectively.

7.5a fuse? Only one I saw was the 140a. I'll check again.

This all sounds so familiar like I've heard someone tell you all of this already today...mmmmm.

You told me to check the 140, hahah.

 

[Drunner97]

I'd start by checking all your fuses, while the main Fusible Link might be okay, I am wondering if your 7.5Amp Alternator fuse may be blown. It sounds like the issue is that the alternator isn't being commanded to charge effectively.

Okay, 7.5a fuse looked fine (and tested good), so for shits and giggles I changed it anyway. On startup, at normal 600 rpms, I get charge. Idled fine for about 30 seconds then something clicked and the idle dropped to 400 rpms and stopped charging.

 

[CrazyNorwegian]

Pulled this from a ford forum:

"Pulled 7.5 amp fuse from position 15 in the fuse block, tested good. Put it back in, started the truck and everything worked perfectly. All voltages checked within the specs on the table that shorod provided. So with my multi-meter in view, I wiggled that fuse a little and the voltage would drop to 12.5 and come back up to 14.4 depending on how I pushed and pulled on it. For now, I wedged a piece of business card in next to the fuse that keeps it pushed to side that makes it work. Who'd uh thunk?"

Have you tried pullin the fuse and putting the same one back in? Maybe bad connection on the fuse block?

 

[Drunner97]

Pulled this from a ford forum:

"Pulled 7.5 amp fuse from position 15 in the fuse block, tested good. Put it back in, started the truck and everything worked perfectly. All voltages checked within the specs on the table that shorod provided. So with my multi-meter in view, I wiggled that fuse a little and the voltage would drop to 12.5 and come back up to 14.4 depending on how I pushed and pulled on it. For now, I wedged a piece of business card in next to the fuse that keeps it pushed to side that makes it work. Who'd uh thunk?"

Have you tried pullin the fuse and putting the same one back in? Maybe bad connection on the fuse block?

Put original fuse back in, cold start idles above 600 and charges, about 10-15 secs later idle drops to 450 and charging stops. Checked torque and it's not throwing any codes when it idles down.

 

[BlackWorksInc]

Let's try something, disconnect the battery for about 10minutes. Then reconnect and start the vehicle and let it idle with no loads on for about 5minutes (If you haven't done a throttle body cleaning in a long time I would suggest doing so during the 10min the battery is disconnected).

After that the vehicle should relearn it's idle and we should have a bit better baseline to work with in terms of idle. I think between all the swapping and disconnecting the idle relearn got a bit off.

As for the charging, so it works when you load it up (i.e. high beams, blower on high, defroster, ect.) and give it a bit of gas? It sounds like it's being throttled down at idle which seems a bit odd, I think this alternator is controlled by the ECM or BCM in that respect but TIS is being a bit vague on that so I will try to get you a better answer tonight.

 

[Drunner97]

Let's try something, disconnect the battery for about 10minutes. Then reconnect and start the vehicle and let it idle with no loads on for about 5minutes (If you haven't done a throttle body cleaning in a long time I would suggest doing so during the 10min the battery is disconnected).

After that the vehicle should relearn it's idle and we should have a bit better baseline to work with in terms of idle. I think between all the swapping and disconnecting the idle relearn got a bit off.

As for the charging, so it works when you load it up (i.e. high beams, blower on high, defroster, ect.) and give it a bit of gas? It sounds like it's being throttled down at idle which seems a bit odd, I think this alternator is controlled by the ECM or BCM in that respect but TIS is being a bit vague on that so I will try to get you a better answer tonight.

Cool I'll give this a try after I finish putting this axle back in. I'll grab some TB cleaner when I drop the slide hammer back off. Not sure it will idle for 5 mins before the battery dies but I'll definitely give it a shot. Maybe I'll throw this battery into the Tacoma so it can get a good charge on the way to autozone.

 

[BlackWorksInc]

Cool I'll give this a try after I finish putting this axle back in. I'll grab some TB cleaner when I drop the slide hammer back off. Not sure it will idle for 5 mins before the battery dies but I'll definitely give it a shot. Maybe I'll throw this battery into the Tacoma so it can get a good charge on the way to autozone.

If the battery is that low, it could cause issues. If you have a battery tender/charger I'd hook up the extra battery to it and let it charge up. You're gonna pull more Amps starting the vehicle than you'll charge up driving (unless the parts store is over an hour away.)