Quick alternator question

[Thatguy]

So I get the low battery light otw home, barely make it home with my edge reading 9v. I pull the 2 pin plug on the back of the alternator to check to see if the computer is calling for the alternator to charge. On the hot wire I got 9v,the ground wire I get 40 ohms . Isn't 40 ohms to high for the ground? I figured it should read a lot lower, didn't know if that was why my alternator isn't charging or not. 

[Me78569]

It's variable ground.  

[Thatguy]

So what exactly does that mean?

[GSP7]

Why dont you just check if the alternator is charging the batteries 12v ++   

[Thatguy]

Because the alternator only charges when it's told to, via the computer. If the voltage regulator/computer doesn't send the output to the alternator to charge, it won't charge. I just wasn't sure if 40ohms to ground was a good enough ground. Still waiting on me78569 to clear that up 

[GSP7]

 

delete

 

 

 

Edited December 21, 2017 by GSP7

[JAG1]

GSP7, Did you figure it out? Usually it's the alternator not the PCM.

 

If you do find a bad VR function from the PCM I think its best to wire your own external VR. You won't need to try and buy a new PCM that way.

 

Alternator ground should be good solid no resistance, but I found my alt. mounting bracket causing resistance to grnd so I added a ground wire from alt. case to neg battery post. Some advantages to doing that, but during battery change out times you can cause damage by hooking up the wrong way if one has too many other wires besides the main cables to worry about.

[Mopar1973Man]

Thre is only the blue and green wire on the back. The blue wire is a constant +12V source when the key is turned on. The PCM varies the ground on the green wire. So if the voltage is getting low the green wire gets more ground. If its getting over charged then the green wire gets less ground. 

 

[GSP7]

7 hours ago, JAG1 said:

GSP7, Did you figure it out?

Well,,,like I said,,,,I always check alternator output first

 

[Thatguy]

19 minutes ago, Mopar1973Man said:

Thre is only the blue and green wire on the back. The blue wire is a constant +12V source when the key is turned on. The PCM varies the ground on the green wire. So if the voltage is getting low the green wire gets more ground. If its getting over charged then the green wire gets less ground. 

 

So do you have any idea if 40ohms means charge or not charge from the PCM? 

[Mopar1973Man]

I would bench test the alternator first thing to see if it passes. Then Check the blue wire in reference to GROUND. Then check the green wire in reference to POSITIVE 12V.

 

Ohms value will be meaningless being your measure a variable resistance. 

[wh82]

When I bought my aftermarket High-Output alternator and had the option to buy an external regulator module that would allow me to adjust the voltage higher than the PCM would.

 

Just found out that my 2004 dakota is PWM and my 2001 Cummins is field current as shown in the diagram @Mopar1973Man posted.

 

Interesting info from the MFG of my alternator(s):

http://blog.dcpowerinc.com/2011/09/09/how-pcm-controlled-alternators-work/

 

I am in no way saying that this companies alternators are good or bad... they definitely do what I need them to, but have mixed feelings otherwise.

 

Edited December 21, 2017 by wh82
correct info.

[GSP7]

Quote

I bought my aftermarket High-Output alternator and had the option to buy an external regulator module that would allow me to adjust the voltage higher than the PCM would

 That is good to Know

 

So did you get the external voltage regulator?

 

Who is a source or vendor of high out put alternators and external regulator for our trucks? Got a lnk?

 

.

Edited December 21, 2017 by GSP7

[Thatguy]

3 hours ago, GSP7 said:

Well,,,like I said,,,,I always check alternator output first

 

Well with my truck running at 8.8-9v when I got home I decided it was best to shut it off and put the battery charger on it. Pulled the alternator off and tested the diode pack. 4 smoked diodes. 

[wh82]

Just now, Thatguy said:

4 smoked diodes. 

 

Ouch

10 minutes ago, GSP7 said:

I was wondering if a High output alternator would have its own built in voltage regulator. Like before the computer controlled cars came out had. Like my 81 Chevy truck

Look at the link I just posted in my edit. evidently there's 2 ways of doing it.

[GSP7]

double post

Edited December 21, 2017 by GSP7

[wh82]

17 minutes ago, GSP7 said:

So did you get the external voltage regulator?

Who is a source or vendor of high out put alternators for our trucks? Got a lnk?

No, didn't feel I needed it.

So there are a few:

* DC Power Engineering

* Mechman

* Irragi

Many many others...

 

I found them before I bought my Cummins because my Dakota was lowering blower fan speeds when running my AC at stop lights, until i accelerated, then the fan would blow faster... the stock alt on that truck only put out enough current at idle to run the computer and spark... after changing my truck actually seems to have more horsepower higher throttle response. so when i bought my Cummins and i found the AC ripple in my alternator and heard the heater blower sag when the compressor kicked in I immediately bought one for it. 200 Amps at idle is a lot of power vs ~30.

 

However at ~650 bucks I still have heartburn over the purchase... The company has had mixed reviews, and it did take a long time to get my parts. The other companies have mixed reviews as well but some of them cheaper with higher claimed output.

 

I just wish the Multiple alternator kits were available for our trucks and not only GM

Edited December 21, 2017 by wh82

[GSP7]

3 hours ago, wh82 said:

No, didn't feel I needed it.

So there are a few:

* DC Power Engineering

* Mechman

* Irragi

Many many others...

 

 

 

I just wish the Multiple alternator kits were available for our trucks and not only GM

 

I would think Denso would have a higher output alternator for our trucks, But googling I sure couldn't find one. I only found a Denso website with a rebuilt 140 amp alternator

 

Mechman. with

External Adjustable Voltage Regulator

http://www.mechman.com/alternators/dodge/full-size-truck/5-9l-diesel/1988-2002/s-series-6-phase-240-amp-alternator-for-early-cummins/

 

These look interesting

http://nationsstarteralternatorv2.commerce-search.net/nav?Year=1999&Make=Dodge&Model=Ram&Engine=5.9L+I6+Cummins+Turbodiesel

 

 

.

Edited December 21, 2017 by GSP7

[wh82]

I think i'm gonna start a chart in a new thread with all the HO alts I know about.

 

 

Edited December 21, 2017 by wh82

[Thatguy]

ordered new rectifier/diode and brushes for 43 bucks shipped. slip rings look good and bearings feel good so I'm going to leave it at that