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Ok Gang...I've got a for sure way to diagnose torque converter lock up issues where it lock and unlocks at about 45-50 MPH. I had a gent call me yesterday with this problem and he's replace both batteries, alternator and the APPS sensor. Attempted all the different wiring issues (adding ground, tinfoil etc.) nothing worked. Like I told him the truck ran 11 years without all this stuff and doesn't require any wiring change to make it work. What it needs is the damaged part to be replaced. So he's returned the wiring back to stock setup.Now I told him to unhook the alternator fuse and take it for a ride... Guess what... No problems! Even though he replaced the alternator it has a damaged diode in it and it bleeding AC noise into the electrical system.So before doing any wiring mods, tinfoil, adding grounds, adding filter... PLEASE! Bench test your alternator! This is the second time I've suggested this and both time resolved the torque converter lock up issue.

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Thanks for the heads up, Mike!Just getting a new tranny and converter in recently and then having to deal with a lockup like this would cause me to flail around on the ground crying like a little schoolgirl thinking I got shafted.If the day ever comes, it will be the first thing I check! :thumbup2:

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What is bugging me to no end is the fact there is all these wild write up of people adjusting APPS sensors, wiring mods, extra grounds, filters, etc. I still say the truck ran fine without any of these mods for 10-12 years and now it needs it... I doubt highly. I say there is a part that is failed and needs to addressed not band-aided over. The more and more I kept studying this and the more I ran into people with this issue and what they done never resolves the issue. But now this is the second phone call where I helped a owner with this issue and found that just unhooking the alternator fuse and the problem goes away tests me instantly the alternator is at fault...Another way to verify...

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Think about it. Really, some poor joe shmo spends hours on trying to fix a simple problem that occurs often. Everyone goes for the band-aid route because no one can or is either willing to spend the time to diagnose the problem.Company's take advantage of you and try and sell you a noise isolator for $25 to fix a TC hunting problem. But in all reality, it is something that lies in the alt. Then not very long later, lo and behold, the problem comes back. $25 down the drain... :banghead:

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  • Board Of Directors

Forgive me I am wrong, not trying to stir the pot, but, I think one of the reasons for the trans hunting is because the voltage regulator is built inside the PCM and VRs put out a ton of RFI noise.Still want to get an external VR installed someday.

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:shrug: Not valid...

Reason being is the truck ran for 10-12 years with out a single issue then now it pops up a TQ Conv lock/unlock issues. Ok still the alternator field is wired up but the output line is open so if the field wiring is the cause then pulling the fuse should of continued the problem but its doesn't. So the only thing on the output line of the alternator is...

Stator -> Diodes ------ Wire ----> Fuse-> Battery

Also being that the alternator starts out with 3 phase AC power got a wonderful source of AC noice if 1 doide is shorted.

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  • Board Of Directors

Yep, I agree now... shows how little I know about this. Just think how much work I have gone thru in my lifetime trying to solve problems and end up only shooting in the dark. Many times.:sick:

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Mike, a couple of questions, which fuse would shut down the alternator/field current. The other question is when I run my digital multimeter across the battery on AC I get roughly 30 volts, I have tried this on 3 other vehicles and get roughly the same voltage, what am I doing wrong or is my cheapy multimeter not up to the task?

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:shrug: Not valid...

Reason being is the truck ran for 10-12 years with out a single issue then now it pops up a TQ Conv lock/unlock issues. Ok still the alternator field is wired up but the output line is open so if the field wiring is the cause then pulling the fuse should of continued the problem but its doesn't. So the only thing on the output line of the alternator is...

Stator -> Diodes ------ Wire ----> Fuse-> Battery

Also being that the alternator starts out with 3 phase AC power got a wonderful source of AC noice if 1 doide is shorted.

Mike,

I understand your argument that the truck ran x amount of years without having the problem. I have been reading about the voltage regulator theory and it makes some sense to me, not that it inherently makes noise, more that in an aged and possibly degrading state that it could become a problem prior to complete failure. Wouldn't your test removing the alternator fuse also shut down the voltage regulator?

Would it be better to get the one wire alternator that has the regulator built in? Thus eliminating the regulator in the PCM (and not having to replace an expensive PCM due to a degrading/failing voltage regulator)

Just playing devils advocate while I'm supposed to be working.

Sincerely,

David Callomon

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  • Administrator

Wouldn't your test removing the alternator fuse also shut down the voltage regulator?

No it doesn't. I just disconnect the charge line because if you kill the voltage regulator you lose the entire PCM and you would have massive amount of error codes and be running limp mode.
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No it doesn't. I just disconnect the charge line because if you kill the voltage regulator you lose the entire PCM and you would have massive amount of error codes and be running limp mode.

Thanks for the quick reply. I am just trying to wrap my head around this entire issue. How long has it been since the first guy put in a good alternator and has no more problems?

- - - Updated - - -

I have done the BD noise issolator on both of my trucks and they don't jump around any more. but like you say I would realy like to know the root of the issue for a proper fix. Noise issolator just makes it tolerable to drive.

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The last gent I talk to did the fuse trick and found out the alternator is bad. Then replaced in a short order of a few day start acting funny again. Pull the fuse sure enough the problem went away. Took the second alternator back and had the store bench test it. Sure enough diodes failed the test. I'm waiting for him to get back with me on the article he's got video and a proceedure drawn up for this...:smart:

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No it doesn't. I just disconnect the charge line because if you kill the voltage regulator you lose the entire PCM and you would have massive amount of error codes and be running limp mode.

Mike, a little off topic........... What about when you decide to put on an external voltage regulator and then take the wire normally going from the Alternator to the PCM and hook it directly to the batteries?:smart: Would that keep the limp mode and error codes out of the Equation? I just don't like Dodges VR, I'd rather have an external one, easy to replace, of good quality. TIA I think you are on target with the bad diodes causing the gear hunting. Still, I wonder about Dodges way of putting the VR inside the PCM. I don't like that design.
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  • Administrator

Once again when hooking up a external regulator you still using the blue with (12V key power) and the greeen wire is used on the the external regulator too.

The green wire is cut loose from the old PCM.

At this point you'll get a P0622 error code because the PCM should sense no changes in the field voltage. But if the PCM regulator is truly dead then it might not even throw the code.

http://articles.mopar1973man.com/general-cummins/34-engine-system/134-voltage-regulator-mod

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(I have had my 2000 auto for two years now and am getting this same symptom more often now. I am usually able to get rid of it with an APPS RESET for 3000 km then it starts. I have a switch and relay to force an unlock of the torque converter without a limp mode or code that gets me by until I have time to reset the APPS.Here is my take on the problem:The alternator produces 3phase AC power and converts it to DC via 6 diode bridge. On an oscilloscope this "DC" signal would have extreme ripple that is smoothed to close to pure DC (neglligible ripple) via the huge storage effect of the two big batteries that act much like a capacitor. A bad diode will create a missing pulse at 0 volts and give a huge spike. The problem is that if the ripple gets to the APPS signal that feeds the PCM with "throttle position" as 0.5V= 0% throttle and 3.5 V = 100% throttle in that there is a problem that the sample can be taken on the ripple spike that indictes falsely that you have suddenly accelerated and want an unlock for power. The next sample sees no spike and locks up again and then it repeats at that critical cruise speed. As an example the computer probably samples about 5 times a second and the pulses are probably several kilohertz (depends on RPM and # stator poles). The threshold for unlock is especially sensitive at that 50 mph mark in my case. What I found is when I put in a Diablo Puck the problem is much worse. I rarely floor the truck with so much power and the "adaptive" software in the PCM adaptively reduces the 0.5 V = 0% to 2.75V = 100%,say, and the problem is bad again and the APPS reset is needed. The reduced dynamic range amplifies the noise effect. I do think that the noise is intoduced via poor ground connections that get worse with age. The PCM supplies a regulated 5Volts to the APPS potentiometer that should be clean (the 5V regulator chip "clips" any minor ripple off) so the alternator noise has to be from ground voltage drop from poor connections as age of truck and rust corrossion makes it worse. Some people get away with better battery connections, tightening/cleaning ground etc.. My next thing will be to check all grounds and put an electrolytic capacitor of about 10 uF 35V right at the PCM APPS input to ground to filter the ripple. The problem is so borderline that it should not take too much effort but I have to say the engineer that designed it did not do due diligence or his budget was way too low! I was in the business myself in my early career as an EE.I'll come back once I am able to get time on this thing.

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Yeah but if the alternator is the source of the ripple and now feeding it to all systems (ECM, PCM, ABS, airBag, Etc.) So filtering the PCM cures the TQ lockup issues but how about VP4 failures, ECM failin, etc... I'm figuring that some of these failures are from the AC from a shorted diode. Why is it that the rest of the problem disappear when the alternator fuse is removed? This why I'm still highly against the idea of using filters, extra grounds, etc... Because all you do is band-aid the problem but the alternator is still beating up every other electronic device on the truck. Why not fix the source of the AC noise? :shrug:Because if the diode failure happens on the negative side then AC pours through the grounds... If it happens on the positive side then some filtering might occur but still most DC electronics are not designed for AC noise.Here is a basic alternator circuit... Take notice there is 6 diodes (3 positive and 3 negative) if I should short out in either side that will be the side the AC waveform leak out on... More diodes fail the worse the problem gets. But in the DC life the gauge will continue to read 14 Volts even though the diodes are bleeding AC wave form. post-2-13869818903_thumb.jpg

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