Alternator charging opinions please (1 Viewer)

[concretejungle]

I'm in the process of going ahead and installing the dual battery system that i've always put off. Part of the reason is i've been chasing some hard starting issues (electrical), weird battery drain (or possibly not getting adequate charging from Alt) and taking the opportunity to upgrade some of the old and brittle wiring. I've upgraded all the wires for the starter, ground wire and a lot more.

I have a larger alternator from the sequoia (unfortunately i don't recall the amperage on it) and I'm using a traditional lead acid battery for starting that i picked up from Costco about 5 months ago. Unfortunately since the truck has been sitting for about 3 months and the darn battery is low. I checked the voltage on it and it read 11.85V. I stuck it in the truck and put the charger on it while i finished connecting the rest of the wires for the starter battery to just get the truck to start up.

Started the truck with the charger connected and it started great. Looked down at the ultra gauge and it's only charging at 13.6V. I used my voltage meter on the battery while it's running to confirm that it was charging around 13.58V to 13.61V.

Normally when i would start the truck the voltage would jump up to 14.25V in the beginning and then slowly back down. This time it never got to 14.0V. I removed the battery charger and there was no change in the charge of the alternator.

My question is do you think this indicates a bad alternator or one on the way out? I also checked my belts because once a long time ago i had a similar issue and the belts were not tight on the alternator, i put new belts on and it charged like a champ. So the belts are tight and they are not too old, maybe 2 years.

 

[baldilocks]

Do you get low charge indicator light on the dash?

 

[John McVicker]

I'm thinking your alternator is ok...just old wiring. Here is how I addressed & solved a similar issue on my 60.

I put a 18" 8 gauge wire fused @ 65 amps (for my stock alt) and ran it from the alternator positive to the battery positive. Back up to 14.2 at idle.

 

[concretejungle]

All the wiring is brand new 2 gauge.

I don't get a low voltage light on the dash. I just assumed since the battery is obviously low it would be putting more charge into it, like 14.25V.

 

[John McVicker]

2g is perfect on your battery, but the wiring that could be your issue is the old wiring in your factory harness.

Also you could put a meter on the actual alternator to determine what it's putting out. Then compare that reading to the battery with the engine running.

If the alternator is putting out 14.0 -14.4 with the engine running, then it's good.


Edit: a bit more info

 

[inkpot]

I assume this was at idle? Did you try reving it up a bit to see if that makes a difference?

 

[concretejungle]

This was at idle guys. IN the past, even at idle it would still get up to 14v or more in the beginning. I tried to rev it up and it didn't really change, maybe a .1 of a Volt.

Regarding the wiring, so i replaced all the ground wires to the chassis and the block, i replaced the wire coming from the alternator to a fuse and then to the battery with new 2guage, i replaced the wire going from the starter to the battery with 2 gauge wire.

Where on the alternator would put the volt meter to test it directly? Im guessing the positive on the positive post and then the black just anywhere for a ground?

 

[landtank]

Be sure to put a load on the circuit before reading the voltage. Usually turning on your high beams will do trick. If you don't see the voltage jump above 14v even at idle you have a problem

 

[concretejungle]

I really don't want to do it, but i'm tempted to try a somewhat experiment. I have a set of new belts sitting on the shelf from Beno.... i may swap them out just to see. I'll do this after i try turning on high beams and checking voltage again.

 

[sbman]

To check the charge state of the battery, disconnect the battery terminal from the vehicle to make sure there are no loads, let it sit for 2-3 hours and then check with a good voltmeter. 12.5-12.7 volts is full charged. 12.0 or less is basically dead. You can do that after you charge it with the charger or after you drive around for a while, and you'll know if it's getting charged or not.

 

[Tools R Us]

To check the charge state of the battery, disconnect the battery terminal from the vehicle to make sure there are no loads, let it sit for 2-3 hours and then check with a good voltmeter. 12.5-12.7 volts is full charged. 12.0 or less is basically dead. You can do that after you charge it with the charger or after you drive around for a while, and you'll know if it's getting charged or not.

This^^^ What is the charge state of the battery? If your attempting to compare charge volt readings with a low/dead battery, it will greatly differ from the expected readings of a fully/mostly charged battery. If low, fully charge the battery and retest.

 

[landtank]

In my experience with checking an alternater's output even after jumping the car because of a dead battery, it has read in the 14.7v range if good.

 

[sbman]

In my experience with checking an alternater's output even after jumping the car because of a dead battery, it has read in the 14.7v range if good.

If the battery has a shorted cell and is consuming a lot of current but not charging, the charge voltage will be low to limit current. The alternator will only put out a certain amount of current before it starts limiting it. The built in regulator does all this. Knowing the charge state of the battery is the first step in troubleshooting a charging issue. The battery is also the easiest thing to replace.

It's a good idea to test the battery under load after it's fully charged as well. The load testers that the auto parts stores have do this well and it rules out any issues with the battery so then you can move on to the alternator and wiring. Even though it's only 5 months old, the battery can still be bad.

 

[concretejungle]

The voltage before i put the battery on the charger was 12.1V. I put it on the charger just long enough to get the truck to start, the charging voltage when the truck started was 13.6V T

I just left it on the charger all night and it's now sat off the charger for about 2 hours and it's currently sitting at 12.93V. When i started the truck the charging voltage from the alternator again was 13.7V - 13.5 V. This didn't change really when i turned the high beams on and the vent blower on... got up to about 13.78V

My hunch is that the alternator is on it's way out.

 

[landtank]

time for a brush kit

 

[sbman]

The voltage before i put the battery on the charger was 12.1V. I put it on the charger just long enough to get the truck to start, the charging voltage when the truck started was 13.6V T

I just left it on the charger all night and it's now sat off the charger for about 2 hours and it's currently sitting at 12.93V. When i started the truck the charging voltage from the alternator again was 13.7V - 13.5 V. This didn't change really when i turned the high beams on and the vent blower on... got up to about 13.78V

My hunch is that the alternator is on it's way out.

Seems like it. The battery was basically dead when you put it on the charger and well charged after you finished the charging and resting period. If it's still losing charge after driving for a while, then alternator or wiring would be the next thing, not as easy though. You might check that the plug on the back of the alternator doesn't have any corrosion or other issues that can cause charging issues as well.

 

[landtank]

have you cleaned the connections at the alternator and battery?

 

[landtank]

also the ground cable. I've replaced a few and they aren't that costly.

 

[concretejungle]

Thanks Guys for the reply.

I actually made new ground cables and while i was at it, took the plug out from the alternator and cleaned it up really well with electrical connection cleaner and then used dielectric grease when it went back together.

I guess i need to start looking for an alternator. At least that's kind of what it's looking like now.

 

[sbman]

I'm running a Tundra alternator also. I bought a Denso unit remanufactured by Denso. Reasonably priced and I have had no issue with it for 30K miles so far.