Alternator or batteries? (1 Viewer)

[Jeff Cooper]

I have a 1HDT that various dash lights stay on for a while after I start it. These lights seem to be staying on a bit longer than they used to after starting.

Both batteries show 12.4v prior to starting.

The voltage on both batteries increases slowly up to 14.2 volts.

The lights go out right about 13 volts on the batteries.

Is this something to be concerned about?

Does it indicate weak batteries or possibly a weak alternator?

Don’t want to pull the alternator and have it rebuilt if it is not yet needed.

Thank you in advance!

 

[rc51kid]

Can you tell us a little more about it? what lights stay on longer?

Honestly i dont know about that engine or the 24v systems. But "strange" electrical problems that cause problems like that are often weak grounds.

 

[93yotasr5]

Can you tell us a little more about it? what lights stay on longer?

Honestly i dont know about that engine or the 24v systems. But "strange" electrical problems that cause problems like that are often weak grounds.

This!

I would check all ground and even replace them with new wires. I did this a while back and it helped me with my electrical demons.

 

[Jeff Cooper]

I am honestly not sure what the lights are but here is a picture of my dash showing the lights

You can see that the voltage is not yet where it should be…it eventually (~10 seconds) get midway between the center mark and 18v.

Again, I am reading 14.2v at each battery once the lights go out.

 

[robnicko]

Is it the original alternator?
If so you may want to check and replace (very easy) the bushes on the alternator as they may be worn down or sticking.

taking a few seconds for the voltage gauge to move up to 'normal' - is there any visible oil leak dripping onto the alternator as it could be the cause. - similar thing happens when washing an engine and water gets in the alternator in that until its dispersed the alternator will show no charge.

 

[Jeff Cooper]

I can only assume it is the original alternator. It is a Denso so I guess I’ll have it repaired.

No oil leaks or water on it. All connections seem fine.

 

[javelinadave]

Auto Zone and O’Riley test batteries for free. I would start there.

 

[MonsterCruiser]

I have a 1HDT that various dash lights stay on for a while after I start it. These lights seem to be staying on a bit longer than they used to after starting.

Both batteries show 12.4v prior to starting.

The voltage on both batteries increases slowly up to 14.2 volts.

The lights go out right about 13 volts on the batteries.

Is this something to be concerned about?

Does it indicate weak batteries or possibly a weak alternator?

Don’t want to pull the alternator and have it rebuilt if it is not yet needed.

Thank you in advance!

When this was happening on my truck I was told the brushes in the alternator were getting worn. It was still working, but it's getting tired. I had a replacement alternator installed and no longer had the delay in the lights going out.

 

[aclos3]

If your alternator is original, I'd certainly start with the brush replacement. For the alternator on the 1FZ, the brush was about $20 as I recall. The most time-consuming part of the job was removing the alternator from the truck, replacing the brush is super easy. I replaced mine when it was about 24 years old and had 235,000 miles on it. The brush was not completely worn out, but it didn't have a ton of material left and would have failed soon.

Does anyone know if the brushes wear faster if you have higher sustained electrical load? i.e. the alternator is spending more time pumping out higher current?

 

[Jeff Cooper]

Thanks to everyone!

Just broke out my tools and am about to remove the alternator.

Thanks again everyone!