Jump to content
  • Welcome To Mopar1973Man.Com

    We can see you are lurking about reading the forums and article databases. We happen to be one of the most friendliest Cummins support website on the planet. Come on and register and grab a inexpensive subscription plan. With that you can unlock even more for you. Technical support either by public forum, private support ticket, and even unlock phone support by Mopar1973Man. Mopar1973Man.Com will remain FREE to read forever!

No Change in AC Readings (Post Ground Wire Mod)


Recommended Posts

Hello all I am back!

 

First let me state that I triple checked all of my work.  No codes are being thrown at the moment.

 

Continuing....I just finished the ground wire mod and I am still getting high readings of .062 at idle and nearing .10 with throttle applied (using a Fluke 87-V).  Unfortunately, I do not remember my initial readings as the truck has been sitting for a short while but I know they were similar to what I am seeing now.  I know of the "second phase" I'd guess you call it with the W-T Mod....new charge wire from aux. battery to alternator (with a fusible link, fuse, circuit breaker, etc.) and adding an extra connection from main battery to aux. battery negative posts.  Would I see any change doing that and/or is it high recommenced to even do in the first place?    

 

Where should I go from here?  Given that I have not seen any change in readings is the alternator at fault then?  Does this line up?  I am running the original Denso alternator with new diodes and brushes.  I should note, I did accidentally arc my cables once (negative slipped out of my hand when removing it and landed on the positive terminal).  Shortly after is when I lost charging abilities to soon find out that my diodes went crispy critters on me.   

 

Kind of bummed out :(.  Was really hoping to see that reading nice and low.  I guess on the bright side I got my rebuilt steering box back from Blue Top and the truck steers a lot better now.  Highly recommend!  

 

Thank You all

Link to post
Share on other sites

Soox,

 

I think you need to test the alternator again.  It is where the AC noise is generated.  The alternator makes AC power.  The diode bridge (rectifier) is designed to take that AC waveform in, and produce as close to a DC wave form out as it possibly can. 

 

Nice simple explanation at basic car audio electronics  ( http://www.bcae1.com/charging.htm  )  

 

Here is a picture of what is happening:

image.png.c378df6fa87a3e7c3a0e1ef2a54266f2.png

 

Notice the rectified output is still wavy. that is "AC noise".   that is what you are seeing.  Those waves in the output get bigger the harder the alternator has to work.  While the diodes are a big part of the AC, there are still the brushes (commutator) also.  

 

Take your alt to an alternator shop.  Tell and pay them to test it, BUT be there.  Ask them to perform the AC test under load.  He may look at you funny (it is not a normal test) explain that the Chrysler (Diamler-Chrysler) electronics are susceptible to AC noise and cause other problems sometimes.   He may have dealt with it enough to understand or he may not completely believe you. (mine didn't... but it was cool when he called his automatic transmission buddy and asked and that guy said it could really be a thing.) 

Anyway, this should help him understand what you are searching for, and he can rebuild it looking for what is causing the high AC.

 

Take your meter with you, if he gets a different reading, use your meter.  if they differ, find a third meter to confirm.

 

HTH

Hag 

 

 

 

  • Like 2
Link to post
Share on other sites
  • Administrator

So far everyone that did the mod had huge reductions in AC noise. The only thing I can say is have the alternator bench tested again and verify its good and not got any bad or weak diodes. To this day I'm still right about 10 to 12mv AC. Alternaotr made it past one year now and still going. 

  • Like 1
Link to post
Share on other sites

Not sure what the post ground mod is that mention in the title. I have done WT's ground mod with very good success. Pre mod .035, post mod .010.

  • Like 1
Link to post
Share on other sites
  • Board Of Directors

The mod is only half done.  Finish the mod before replacing the alternator then retest the ac output.

  • Like 1
Link to post
Share on other sites
22 minutes ago, IBMobile said:

The mod is only half done.  Finish the mod before replacing the alternator then retest the ac output.

Yes.  I will be replacing the charge cable very soon.  I wasn't sure if only rerouting the four grounds would show any significant drop.  Could someone clarify on doing the additional battery to battery negative connection.  Is this necessary?  It has to do with the temperature sensor on the main battery, correct?  @Mopar1973Man I believe you said in a recent post that assuming if both batteries and cables are in good condition then it would be fine the way it is without adding that negative cable.  @dripley Was referring to after when I said post.  I apologize.    

 

Thank You all

  • Like 1
Link to post
Share on other sites

I just ran a #4 cable from the parts store for the additional ground and ran it on the radiator just like the +. It is not expensive and easy to do.

Edited by dripley
  • Like 1
Link to post
Share on other sites

You have leaking diodes in your alternator. While these mods that you're doing do help the batteries dampen some of that AC noise, you have to fix the source of the noise. I would also put a noise filter on the TPS signal line at the PCM as part of the process.

  • Like 3
Link to post
Share on other sites
  • Administrator
5 hours ago, Dynamic said:

I would also put a noise filter on the TPS signal line at the PCM as part of the process

No.. Please don't. That creates a masked problems. Best to leave all filters off the system fix the source. Don't mask with filters.

  • Like 1
Link to post
Share on other sites

I didn't say not to fix the AC problem, but I'd definitely shunt as much of the remaining AC on the TPS circuit to ground as you can. The electronics in those 2nd Gens were too sensitive to AC ripple even when they were new, and haven't gotten any better in the last 20 years as they have aged.

Link to post
Share on other sites

Here is my experience. Please note that I'm no electrical guru, but still did and am doing the mod, and have seen the results. ...

 

Besides alternator problems that result in high ac noise, I believe the charging cable has something to do with it. I would be curious if somebody changed there 6 guage wire running across the front with a new 6 or 4 guage while still running across the front, to see if the noise would still drop. Theory being that possibly the cable has aged and doesn't properly carry current like it should.(again, my theory, but im kinda retarded so don't put trust in that 100%, or 50% for that matter :cookoo:)

 

But, I have done the charging cable half of the mod only so far, running a new cable (4guage) with fuse inline to passenger battery. And the drop in ac was very noticable. I have also run 1/0 ground from battery to battery(i did this first before charging cable) I have not done the ground mod yet. I believe that part helps ground your important components quickly without dragging it across the the whole engine compartment just because of poor design.

 

So do a new charge cable, and you should see ac drop. You can see what the difference is on the wt mod article on the last page. I was seeing as high .08 at one point, .06-.07 being the average. And it dropped alot.

Link to post
Share on other sites
  • Board Of Directors

That's why all the mods get done along with clean body/chassis grounds and good batteries, then test the alternator ac output.  

  • Like 2
Link to post
Share on other sites
4 hours ago, IBMobile said:

That's why all the mods get done along with clean body/chassis grounds and good batteries, then test the alternator ac output.  

I have to agree the whole mod is the way to go. While no electrical guru by any means my whole system seems to be much happier with the mod. NO electrical gremlins to deal with.

Link to post
Share on other sites
1 hour ago, Alexio Auditore said:

Did you run a new charge cable to passenger battery or driver? Just curious.

New charge cable is to the auxiliary battery.  I just need to add the extra wire between both negative terminals on the batteries.  Should arrive soon.      

Link to post
Share on other sites
×
×
  • Create New...