Battery voltage

I got a 2012 regular cab. 2.7l. I have a ultra guage and noticed the ecm voltage will drop down to high 11 or low 12 volts sitting at a red-light in gear. The minute I take off it jumps back up to 13.5. Sitting with it in park the voltage will be in the low 13 volts range. I know voltage should be 13.2 or higher. Has anyone else experienced this?

 

You should take a reading directly off the battery with a multimeter. I've found that some devices that read battery voltages will incorrectly report what the actual battery voltage is at. As long as it's 13.2v or above at operating temp idle, you're ok.

 

alternator output varies with RPM. It will put out less at 600 rpm than 800, however, in a healthy system this shouldn't result in much of a voltage drop. Either your electrical system is drawing a lot more current than normal or your alternator is beginning to show signs of struggling. Best to confirm these readings at the battery though.

However, it should be dropping to high 12's, not 11. You need to let the car rest about 2 hours after driving and measuring the resting voltage of your battery. Should be around 12.6-12.8. If it is 12, you need to be looking at new batteries.

 

I have a battery tester/alternator tester at work. When I get off I'm gonna test both. Battery was replaced 2 years ago

 

Hows your idle speed?
Low idle speed from a dirty throttle body can cause the alternator to drop out.

If that's good and the belt isn't slipping then the alternator is likely on its way out.

 

About 600 to 650

 

That idle speed is a little on the low side. It should be more like 700 to 750 in park in an automatic transmission 2.7L (after it's fully warmed up). Inspect the throttle body to see if it should be cleaned and then see if there is any improvement.

 

It may be closer to 700. I will check again when I get off work. Tested the alternator and it tested good but battery was charge and retest with 12.1 volts after sitting for 4 hours. So I know where to start.

 

This chart gives you an idea of battery health vs resting voltage. Note that for a lead acid battery operating below 50% is actually damaging the battery. So your reading of 12.1V pretty strongly points to a battery on the way out.

 

This was from my battery tester at work

 

A fully charged battery is 12.6v
You can not get a true state of battery reading unless you test it fully charged (or close to charged 12.4v+. But 12.6 is ideal)

You need to see if the battery will charge to 12.6v
If not, replace battery
If so, Check battery again when fully charged.

You are dropping down close to 10v. You don't typically want to see it fall below 9.7ish volt when cranking.
But your battery wasn't fully charged when tested.

Again, Charge battery and retest.

 

I’m not familiar with that tester. Looks like 10.17 is average cranking volts, but the drop is way down around 7. Like TnShooter suggested, charge it, test again.

 

Not sure if I'm going to mess with it anymore. I've been needing a 4 door truck due a baby on the way and I just found a 2016 tacoma double cab 4wd that I will probably trade for

 

Check the timing cover for leaks.
That’s $2,000+ job.

Other than that, Good luck
Hope you get it.

 

It's leaking. Having it added into the price of the truck. They are wanting 25,000 for. They are giving me 12,000 for my single cab

 

@Bishop84 help this guy man.
Can you give us a rough estimate on what labor and parts run for that leak.
Want to make sure they give him enough to "get it fixed".

On a 16' you need to replace parts too.
Don't let them just give you labor. Make them give you parts.
Water pump, coolant, belt.......

 

Well according to Mitchell it pays about 19 hrs so multiply that by the going labor rate in your area to get your aprox labor cost.

It shows to be an engine out job so depending on mileage and condition there may be some other things to consider replacing/resealing while it's out.

 

They estimated $1,900 said he can give me a better deal if I buy the truck

 

Dropping the front differential is the "shortcut".
But I have a feeling OP is going to get screwed on the allotment for replacement.

 

Better get that in writing.
Like OUT THE DOOR price for the fix.
I wouldn't touch it for that price...Not with parts included.