Battery/Voltage question

[phix-]

What would cause a HO alternator to push out 12v in Drive but 14v in neutral (also 14 in park)? In D if you sit with your foot on the brake the truck will begin to sputter some until it gets low enough and then just shuts off.

 

[matt0248]

Your engine idle speed it too low when in drive. Whatever is causing the low idle problem is causing the low output from the Alternator becuse the pulley is spinning too slow.

 

[Dono]

Still fighting with this Phix? I hate these nagging issues.

What I have heard about the HO alternators (No first hand experience) is that at low revolutions they don't produce any current. Once the revs pick up, they really produce a ton though.

Hows your battery? I was able to drive a good half hour to get to work with no alternator at all (Of course, headlights were not on, and radio was off).

Your battery should support your ignition system for periods of idle, shouldn't it?

 

[Torqueranger]

Read this

 

[Sedition]

Hmmm..., I'm gonna have to ask some questions.

What are you running with the alternator when this happens?
What did you purchase the high output alternator to run?
Do you have the regulator plugged in?
Do you have a winch or other high powered electrical device?
What is your battery voltage when the truck is not running?

 

[phix-]

Alternator is from Mr. Alternator
It is a 200amp
Reason: Added gauges, added H.I.Ds, audio system. With more to come possibly, plus my volt. reg on the last 130amp was sketchy.

So here is the info:

Battery shows 13.9'ish running (at terminals)
Battery ground shows 13.8-9'ish
Alternator post: 14.1'ish
Power cap: 12.4-2 engine off

So the issue is ONLY when in D (drive), if its in Park or Neutral it shows 14.4 at my power cap engine on. If I leave it in Drive it starts to get sloppy and drops till about 12 and shuts off. Scary part is I drove to work today windows down no a/c my audio semi turned up and it shut off on me going down the road. Power cap showed 12.2 at the cap but the truck REFUSED to start. I pushed the behemoth with the help from a mini van owner, I had my own cables so he gave me a jump. Drove the truck all the way to work no issues (unless I kept it in Drive at a stoplight). What is odd is that after I put it in N at a stop the battery gauge bounces right back up and I get an OBD-II reading of 14.4.

Side note: the white/black stripe connection (going into the volt. reg.) does really click into place its actually scary how easy you could just pull the wire and it slides off. Could this be an issue?

 

[Dono]

Ok, Phix, can you do a test for me?

Have someone in your truck with it running, and the transmission in drive with the brake on.

Measure at the power cap.
Now, have the person in the truck raise the rpm's (foot still on brake) to what idle would be with the truck in neutral. Measure voltage again.

Did the voltage go up as if you were in Neutral?
If not, what could be the difference in consuming power from Neutral to Drive? If the rpm's are the same in Drive, as Neutral the voltage should be the same.

 

[phix-]

RPM wise on the cluster they are the same. Even more strange if I have my foot on the brake there is no different effect unless in N vs D. Any time its in D it just slowly starts and then before you know it (within a light changing and coming to a stop, waiting, and taking off) you get this slow drop off. It takes about 40-45 secs to get down to 13, but gets into 12. Now if I put it in N, the battery gauge climbs right up to the middle and I see 14.4v. The package looked like it went through some hell getting to me so Mr. Alternator sent me a new volt. reg. going to try that tomorrow hopefully and see if it clears it up. I also have smaller pulley on my older alternator from what I can tell (its not that stock black one). I am curious if I throw that on there (after swapping volt. reg) if it will help?

 

[Dono]

It just seems strange.
With your alternator running at the same speed in both Drive and Neutral, you should get the same voltage output from the alternator.

 

[phix-]

Yea.. something tells me the regulator may be the issue. If not then I have an odd issue to work through.

 

[2000StreetRod]

brake light short?

If the engine speed is the same in Drive as Park and Neutral then the only difference I can think of is the brakes. Step on the brakes when in Park and see if the voltage drops like it does in Drive. Maybe there is a short in the brake light circuit.

 

[phix-]

Even more oddly it doesn't do it in N or P only in drive with brakes. Uploading a video now, thoughts on that white/black stripe connection?

 

[Sedition]

I would do something to make that regulator connection solid. But even with the regulator set to give you full voltage all the time I don't believe it will be enough to stall this engine, even with a HO Alternator.

What happens when you sit in "Drive" with the hand brake applied and your foot off the brakes?

Also you mentioned that your battery sits at 12.2V to 12.4V when the truck is off. That seems kind of low to me, I have tested a ton of automotive batteries and the good ones sit at 12.65V. Although the voltage is not low enough to have a dead or shorted cell. I don't think this will cause any problems in the short term.

Do you get a flat battery sometimes in the morning when you go to start your truck?

This might sound like a stupid question but, are the battery cables connected to the terminals tightly and don't have any cracks or anything in them? Sometimes they look tight but they may not be tight enough because they have fractured where you can't see. If your battery is not connected to your electrical system well or not connected at all, the truck will die exactly like you are describing.

 

[phix-]

Swapped volt. reg. today and no more stalling in D. when I looked at the 2 in comparison you could see one looked like it suffered a huge fall which makes sense because when the box arrived part of it was sticking out of the box. Not cool, but with the a/c on it gets down to 13 at idle but that is as far as it goes. Also replaced both upper arms today so truck rides nice.

 

[phix-]

Ok so it turns out I was slightly wrong. It is not entirely the volt reg. it is actually the wire harness on alternator. When an exploder alternator fries or dies, it takes the wire harness with it. My bet is that one of the wires was not even working. The wire in question controls the output of the volt reg. at Drive function and the opposing wire controls Neutral and Park. The wires in question are the following:

Green/Orange stripe
Yellow/Red stripe

Both are on the harness, I could even be wrong here saying that it is these wires when it could even be the White/Black stripe. Any how I replaced the harness and no more funky loss from the new H.O. Alternator from Mr. Alternator.

 

[Dono]

Nice! Another issue taken care of. Great info.