Alternator Output Low At Idle (1 Viewer)

[Cruzerman]

Hoping for some insight into my alternator. I hooked up a volt meter right at the battery. At idle, the volt meter reads 12.5 volts. Shouldn't it read higher? However, if I kick up the RPMs, it seems to work fine, going up to 14.5 volts. Is this normal?

TIA

 

[bajaphile]

12.5V is too low.

The FSM states to check the voltage between idle and 2000 RPM and should be between:
13.5-15.0 V depending on temp. (Higher temps would result in lower voltage).

I believe at idle my volt meter reads 13.5V

 

[BILT4ME]

Hoping for some insight into my alternator. I hooked up a volt meter right at the battery. At idle, the volt meter reads 12.5 volts. Shouldn't it read higher? However, if I kick up the RPMs, it seems to work fine, going up to 14.5 volts. Is this normal?

TIA

It's probably on the way out.

I would sit at a light and watch my voltage output start at 13.7V and drop to 11.6V. I was able to catch and replace my alternator BEFORE it became a problem and stranded me. I have an UltraGauge that I monitor my stuff all the time.

Start shopping for a replacement or a rebuild kit.

 

[midfat]

I’d highly recommend the @Photoman upgrade kit. If you’re already considering a new alternator, might as well jump up from the stock 80A unit to a 120A or 150A Sequoia alternator. And it comes with an under-drive pulley, so you’ll have full juice at idle. I did the upgrade a few years back and it’s been flawless.

 

[jonheld]

Hoping for some insight into my alternator. I hooked up a volt meter right at the battery. At idle, the volt meter reads 12.5 volts. Shouldn't it read higher? However, if I kick up the RPMs, it seems to work fine, going up to 14.5 volts. Is this normal?

TIA

Yes, it should read higher. With the engine running with no accessories on you should be around 14.4 VDC.
However, a faulty battery cell can drag down the system voltage until the alternator can put out enough to compensate.
I would have the battery and all connections tested first, then the alternator.

 

[Cruzerman]

Battery and cables are good. Again, seems to work off idle, just not at idle. While I would like to put in a higher output unit, not a priority in this rig. Would this most likely be a case of just replacing the brushes?

 

[jonheld]

No real need for a high output unit IMO, but I like to keep it simple.
Start with brushes and see what happens. You could have it tested, but you'll have to find a reputable shop.

 

[leonard_nemoy]

My local alternator shop tested mine and said 12v was normal at idle, with just a little throttle (850rpm) it went to 14.4 v. The tech explained that alternators are designed to charge under load. That was 5 years ago and mine is still going strong with no dead batteries.

 

[Tools R Us]

What is the resting voltage of the battery?