Alternator charging

[michael evans]

I made some logs with the XFI and saw that voltage was 12.7 even while going down the track. I installed a new alternator to see 13.5 when I first started the engine then it went down and back to 12.7.

What the _____ ? Is there a resistor that only lets 12 volts to the computer ?

 

[Boost231]

I made some logs with the XFI and saw that voltage was 12.7 even while going down the track. I installed a new alternator to see 13.5 when I first started the engine then it went down and back to 12.7.

What the _____ ? Is there a resistor that only lets 12 volts to the computer ?

Fighting the same issues. Wish there was a easy way to keep the voltage at a solid 14.2

Sent from my SM-G935T using Tapatalk

 

[mikestertwo]

I made some logs with the XFI and saw that voltage was 12.7 even while going down the track. I installed a new alternator to see 13.5 when I first started the engine then it went down and back to 12.7.

What the _____ ? Is there a resistor that only lets 12 volts to the computer ?

Fighting the same issues. Wish there was a easy way to keep the voltage at a solid 14.2

Sent from my SM-G935T using Tapatalk

Alternators have temperature compensation built into the regulator that's why the voltage drops when they warm up. If you want to raise the voltage a little wire in the sense line on the alternator.

 

[turbo nasty]

Very common to have a volt difference in car. With car showing 12.7 on xfi check the battery under hood and see if its the same.

 

[RUQWKNF]

Do you see the Voltage light come on when you first turn the key? Key on, not running.
If not, the circuit is faulty and the alternator is not charging the battery.

Caspers Field Fix harness is the quick fix.

If yes to the light on the dash at key on, I would inspect the alternator charging wire from alternator to battery. Replace if necessary.
It could also be a dead cell in the battery.

-Patrick-

 

[michael evans]

Alternators have temperature compensation built into the regulator that's why the voltage drops when they warm up. If you want to raise the voltage a little wire in the sense line on the alternator.

How is that done ?

 

[michael evans]

Very common to have a volt difference in car. With car showing 12.7 on xfi check the battery under hood and see if its the same.

At the battery it is about .6 higher

 

[MikeS]

Took my car for a spin at night for the first time in a while and noticed the volt light flickering with everything on (alky, headlights, gauge lights, etc....) Switched the scanmaster over to the batter voltage setting and saw it was dropping from 13.5 at idle into the low 12's/ high 11's, even on moderate acceleration. I already have several extra 4 gauge ground wires added to the electrical system.

Going to try swapping the old 8? gauge wire from the alternator to battery over to a section of 2 gauge wire I have laying around. If that doesn't work I'll see if a local alternator shop can rebuild my stock one to a 200 amp unit. I'll post back up the results in the event it helps you.

I think someone in an older, similar thread mentioned putting a 3a 50v diode or two from Radio Shack in line with the sense wire to boost voltage, but I don't know how that is done.

 

[michael evans]

Do you see the Voltage light come on when you first turn the key? Key on, not running.
If not, the circuit is faulty and the alternator is not charging the battery.

Caspers Field Fix harness is the quick fix.

If yes to the light on the dash at key on, I would inspect the alternator charging wire from alternator to battery. Replace if necessary.
It could also be a dead cell in the battery.

-Patrick-

New wire from the battery.
Have the Caspers field fix on.
Batter is a new (about six months old) O

 

[No disintegrations]

By chance does have underdrive pulley? Does voltage change at all when rpm is raised ?

 

[michael evans]

It does have an underdrive pulley.

The voltage does increase with RPMs.

 

[No disintegrations]

Well, that's that. Just throw on stock size pullies and it should be gtg

 

[Mr.Spool]

I made some logs with the XFI and saw that voltage was 12.7 even while going down the track. I installed a new alternator to see 13.5 when I first started the engine then it went down and back to 12.7.

What the _____ ? Is there a resistor that only lets 12 volts to the computer ?

does the car have a volt booster?

 

[michael evans]

No volt booster

 

[Pronto]

It would be worth it to try a stock pulley to see what the volts look like.

 

[michael evans]

Looking for one.

Only bad part is having to drop the intercooler

 

[RmvBfrFlght]

Look for a slightly smaller alternator pulley. I run one along with an under-drive crank pulley. This slows the P/S pump and water pump with no ill affects. But allows a good system voltage.

RemoveBeforeFlight

 

[RUQWKNF]

Yes, smaller dia crank pulley with the rest of the pulleys being stock dia, will definitely cause your symptoms.
Either stock diameter crank pulley from RJC, Cruz or GN1, or change the alternator pulley and keep yours.
Years ago, I was given an old school billet aluminum smaller diameter ATR underdrive crank pulley. Not only did I have the same symptoms, but it also killed the power steering pump and the alternator on my "86 T-Type. That pulley wound up being an expensive fix back then.

 

[Nick Micale]

Well, that's that. Just throw on stock size pullies and it should be gtg

For years I have seen my voltage drop at high RPM from 13.9 to 12.2 when over 6000 RPM using Autozone and other reman alternators.

Info from a local electrical rebuild shop said that our alts have a built-in provision which lessens voltage at higher RPM's.

I then examined my current alt, and found it had a pulley which is smaller than stock?

Having some stock alt cores, I installed the larger stock pulley which resulted in less alt RPM, and more stable voltage.

 

[michael evans]

Have a new smaller alternator pulley coming since all that I have here are the same size.
Once I have it on, I will report back.