I found the following thread on this:

https://dodgeforum.com/forum/dodge-r...g-problem.html

I have a 96 Dodge RamVan 2500 that I have a hard time to keep running at idle once it's warmed up. What happens is you can see the voltage fluctuate from 14 to 15V like it should be, down under 12V. At times, pulling into the driveway kills the engine. If I'm driving down the road, I see no problem, full charging without issue. It's not until I slow down and get near idle that it starts dying.

I took it up to the shop and they rewired a lot of stuff around the battery. I have a single battery, and it was replaced less than a year ago due to problems I had with the original battery. So there's a new battery, new leads, and new wiring. It does have an alarm in place that goes somewhere in between the alternator and battery, and I also have the standard battery protection circuit in place, with a button inside. Clearly something is not right, and I'm not paying someone to give it back to me with the same problem I brought it in with.

I was also told that my transmission was shot at the shop, and that it does not have a 1st gear. I'm curious if there might be some sort of transmission switch? I will get a second opinion on the transmission, but they are probably right. Point being, not to sink a bunch of money into something that is going to end up costing a lot more pretty soon with a rebuilt tranny.

 

Have not yet checked the alternator, but I figure that if I have an alternator problem, that it would appear, even when applying gas down the road, and the problem disappears when I'm driving.

 

The condition sure sounds like an alternator problem. There are two types known for our Magnum engine's. The alternator with the large pulley and the one with the small pulley.

Ram Vans from 1994-1996 had the large pulley. When the belt drives it, the alternator puts out 12.6VDC to 12.8VDC with the stereo, headlights (hi-beams), AC on max, wipers, and HVAC blower on high.

Ram Vans from 1997-2003 have the small pulley. When the belt drives it, the alternator puts out 13.4VDC to 13.8VDC with the stereo, headlights (hi-beams), AC on max, wipers, and HVAC blower on high.

1992-1996 Alternator pulley large size = 2.85-inch
1997-2003 Alternator pulley small size = 2.47-inch

If you were to get a new alternator, measure the pulley size. The smaller pulley will spin faster when driven by the belt. Thus, more energy being developed. ALSO, I would highly recommend having the IAC cleaned (or replaced) since it does control the idle speed. If the IAC is dirty or is failing, the idle will drop along with the voltage more than what the engine needs to run.

ALSO, the TPS voltage needs to be about 0.685V to 0.75V for proper stat-off from an idle. Not all factory or replacement TPS parts sit in this range. Some are at the bar minimum of 0.3V and that can be a hidden problem that causes all sots of grief before finding it.

 

Thanks a lot for all the ideas. I'll measure my pulley first thing I can tomorrow. The symptoms I am seeing leads me to really think hard about cleaning/replacing the IAC, I will try this first. Found the following thread on cleaning it:

https://dodgeforum.com/forum/dodge-r...n-the-iac.html

 

So you are saying that either of the alternators will work on my 96? I would prefer higher output voltage, of course.

 

Dude, thank you so much for this! Unhappy to say that I was stooped for about $120 from our local garage. They blamed the wiring and re-wired my battery terminals and ran new cable. It needed it anyway, but didn't solve anything. 30 minutes cleaning the IAC did the trick. There is also a guide right here, and describes my symptoms down to the tee. Problem solved!

https://dodgeforum.com/forum/dodge-r...n-the-iac.html

 

Glad the cleaning worked on the IAC. Guess what, I wrote that DIY a few years back. It's saved plenty of people $$$ to do the job themselves.

 

Um, duh... Wow, I'm really observant, aren't I? Thanks for the tutorial, and again, it's GREATLY appreciated.

 

would just like to know a little more on the Alternator that you mention Stev. what be the normal output from the earlier version of alternator as those values you mention for full use is not really high enough to charge a battery.

 

Many factors decide the alternator voltage.

The voltages will be very different depending on the batteries state of charge, and state of health and engine RPM and how long the engine has been running.

Just know that the alternator does a poor job squeezing in the last 20 %. It takes a long long time, and multiple short trips driving will never do it, So if your the type to use battery power with the engine off, you cannot just say that it outputs x volts and x amps every time you drive.

The voltage regulator keeps the voltage from going and staying too high when the amps taper way down.

My voltage regulator does a pretty good job keeping my batteries under 14.5 volts when my 3 batteries are low and sucking 40 to 90 amps from the alternator.

But when they are full, or nearly so, I will see 13.6 to 13.8 volts and only 3 to 6 amps going into the batteries. The Amps taper way down when the battery approaches the 85%+ stage, depending on the general health and age of the battery.

So if you see these low numbers, do not condemn the alternator, consider the possibility that the battery is at or very nearly at it's full capacity. If it is an old battery or an abused and chronically undercharged battery, this capacity might be a small percentage compared to when it was new.

So unless you know the state of charge of the battery(which is not easy/convenient to to accurately figure out/know) you cannot say whether or not any particular alternator is not upto the task, UNLESS it cannot ever get a known healthy battery upto 14.4 volts when you know the battery is more than 25% discharged. Higher engine RPM1200+ are generally needed to get a depleted battery up there, and mine can take several minutes of pumping 60+ amps into 3 depleted batteries before 14.5 is reached.

At Idle speeds when my alternator is warm, the maximum amps is about 32, and with very depleted batteries the voltage will then fall again cause they are so thirsty and the low rpm alternator cannot keep them up in the mid 14's.

And I have seriously upgraded my charging circuit cabling between my alternator and batteries. The Stock cables are barely adequate, and I would blame them and all the connections between alternator and battery including grounds before condemning any alternator of not being "big" enough.