Charging Issues?

[Dous]

Well I guess I am stumped, I will admit electrical issues are not my strong suit.

So there I was at the school house, everything was going well until I got into the 4runner to drive home. I noticed the charging system light came on.

I made it home no issue, then began trying to diagnose the issue. I figured the reman alt I purchased last year had shit the bed. I pulled it and took it to Advance

We tested it 3 times, output voltage was at or above 14v all times.

My battery is a brand new AGM unit, which I am sure is good to go. Both terminals are clean and tight.


What else could it be? I need to get a voltmeter I guess and see if that narrows anything down. Would a bad voltage regulator put the charging light on? If anything it would be too much voltage, but maybe it accounts for that?

Thanks for any insight!

 

[19963.4lsr5]

You need to read your battery terminal voltage with engine running. It should be above 13.5 at idle depending on temp. and then turn on lights and heater fan on high.

My 97 runs at 14.3v darn near all the time.

 

[LittleCaesar]

Try this:
Voltage Drop Testing

Don't rule out the wiring (connectors and all).

 

[IBallEngineer]

Try this:
Voltage Drop Testing

Don't rule out the wiring (connectors and all).

Don't rule out anything. Bench testing is good but you need to check the car, not just the parts. No part is good just because it's new, you have to confirm. Start with the voltmeter test, both at the battery AND at the fuse box!

:snacker:

 

[Dous]

Thanks for the replies guys!

So at the battery I got 14.4v with the truck running, which is good!

How do I check at the fusebox appropriately?

 

[Dous]

Okay, checked it at the fusebox, also 14.5 volts

So the light is still on even after resetting....what gives?

It seems like the system is charging appropriately

 

[19963.4lsr5]

Try replacing the bulb. There is some special resistance needed. On the GM slots that operate like the DENSO the resistance is important.

 

[IBallEngineer]

Okay, checked it at the fusebox, also 14.5 volts

So the light is still on even after resetting....what gives?

It seems like the system is charging appropriately

I should have asked this sooner, but does the light turn on when you turn the key on with the engine off?

 

[Dous]

I should have asked this sooner, but does the light turn on when you turn the key on with the engine off?

Yes sir it does

 

[IBallEngineer]

Yes sir it does

OK, so that confirms the circuit is good to the light on the fused end. And all the way to the alternator. Now the key is understanding how Toyota turns the light off.

In the early systems the light would be turned off when the field circuit generated voltage, thus cancelling out the ground. In the IC regulator this isn't always the case. In the case of these Toyota alternators, the L terminal(T1 Yellow/Green wire) operates the light.

My understanding is if check the voltage at that terminal with the engine running it should be battery voltage to turn off the light. I'll have to confirm this and get back to you.

:help:

 

[the great him]

[MENTION=51127]Dous[/MENTION], i had the same issue on my old runner last year, chased the problem for a couple days and stupidly didnt use the volt meter like you have to test...

anyhow i ended up upgrading to a CS144 alt, even though my stock alt was pumping out good power -glad i did upgrade though, as when i swapped, i found that the bearings in my stock denso were about to chit the bed.

anyhow just after i ordered the new alt, i decided to start testing with the volt meter and found everything within spec, but still had the light. then i started looking at the wiring and noticed that one of the wires coming off the plug on the back of the alt has a crack/break in it and if i moved it ever so slightly the light would go off... these wires deal with heat all the time -from the exhaust and the electrical load on them, combine that with the age of them and its no surprise(actually more of a surprise its not more common) that they crack and trigger that light. -you can buy a new pig tail from toyota for like $30 i think, i got just the wire kit and redid that and then installed the new alt and harness conversion.

anyhow yeah get in there and gently wiggle or move those wires a little while someone sits in the drivers seat, and see if that light goes out, if it does thats your issue. im gonna bet money on it. i have seen a couple of these now that i have been looking for this on other peoples rigs. good luck!

 

[Brveagle]

Great information in this thread.