98 Caravan AWD.....low voltage only at idle

Status
Not open for further replies.
Joined
Jan 11, 2007
Messages
670
Location
va
I have been chasing this problem for the entire 5 years that I have owned it.

When I run several accessories at idle, the voltage drops. It doesn't matter what accessories are run, I just can't run more than a few at the same time.

If I rev the engine higher than 1500 rpm, I can get 13.8 VDC with all of the accessories running.

The voltage slowly drops from about 12.8 VDC down to the high 11 volt range with all of the accessories running.

This really concerns me since in this area a 60 mile commute is typical and can be bumper to bumper the whole way.

Things I have tried:

3 different alternators.
Cleaning and sanding numerous ground points.
2 different batteries
4 gauge wire from negative terminal to strut tower.
Bypassing the ECU based voltage regulator and installing an external regulator.
New serpentine belt and tensioner.
Fresh battery terminals.
Holding 4 gauge wire from negative battery terminal and connecting it to different parts of the chassis to see if voltage went up.

I really love this van and have resolved many of it's issues. I just can't figure this one out and neither can anyone on the caravan forums.

Any ideas?

Thanks
 
What accessories are you running and are they stock or aftermarket? Should the ECU be upping the idle with the extra electrical load? I know next to nothing about automotive electrical systems so I am just spitballing here.
 
Originally Posted By: NMBurb02
What accessories are you running and are they stock or aftermarket? Should the ECU be upping the idle with the extra electrical load? I know next to nothing about automotive electrical systems so I am just spitballing here.


Great questions. All stock.

A/C, headlight, and radio.

...but the same will happen with wipers, headlights, and radio etc.

Too much current draw and it's over.

After running the 4 gauge wire between the strut tower and ground today, idle jumped up to between 1500-2000 rpm, so I had thought about that. Voltage was a bit better when this was happening....at least in the low 13 volt range with a few accessories running.

I was concerned that the vehicle would overheat with a high idle for extended time, so I shut it off for a second and then started it back up.

The high idle went away and the voltage drop continued.
 
What is the RPM during all of this? 600? 800? Is the electric defroster stuck on? Perhaps the throttle body is dirty or the Idle control motor is slow letting the idle lag behind.
 
Originally Posted By: WobblyElvis
What is the RPM during all of this? 600? 800? Is the electric defroster stuck on? Perhaps the throttle body is dirty or the Idle control motor is slow letting the idle lag behind.


I can't remember the exact rpm...but I checked into that possibility. The rpm is definitely stock for the vehicle....whatever that means....like 800 rpm maybe.
 
At low RPM you are running off the battery and not the alternator there.I have seen that happen when there is not a good connection between the battery and the cables/ends.Changing batteries in the past,I have had that happen and had to remove the clamps and clean/reattach the clamps.If you have "temporary" battery clamps and not soldered on ones I would suspect that as a problem.Use those cast type clamps and the solder slugs to permanently attach the two together.Works on my K...
 
Originally Posted By: NHGUY
At low RPM you are running off the battery and not the alternator there.I have seen that happen when there is not a good connection between the battery and the cables/ends.Changing batteries in the past,I have had that happen and had to remove the clamps and clean/reattach the clamps.If you have "temporary" battery clamps and not soldered on ones I would suspect that as a problem.Use those cast type clamps and the solder slugs to permanently attach the two together.Works on my K...


I have never seen solder lug type battery terminals, would you mind posting a link if you know of one so I can see what they look like?

I use these on a few of my vehicles and have never experienced this problem so not sure that the clamps are the cause.

http://shop.advanceautoparts.com/p/autoc...ttery+terminals
 
New battery terminals? How are they attached to the cables? Those are not the best choice for cables yep they are temporary though that might be the problem.at are you using to check the volts? Is the fan belt slipping? Could the pulley on the alternator be the wrong size? And the basic stupid question have you tried to find another like van to compare the volts?
 
Originally Posted By: CT8
New battery terminals? How are they attached to the cables? Those are not the best choice for cables yep they are temporary though that might be the problem.at are you using to check the volts? Is the fan belt slipping? Could the pulley on the alternator be the wrong size? And the basic stupid question have you tried to find another like van to compare the volts?
Quick release... how often do you use that "feature". Get some terminals with a nice big threaded stud and nut for the cable connection and attach a good quality copper lug to the cable, place on the stud and tighten. BTW, you've had THREE alternators? By this time I'd be looking at car audio vendors for a "high output" alternator rather than another stock one. 150 amps would be nice. You can't get blood out of an stone. MY son's restoring a BMW 633CSI> A prior mo-ron of an owner had the BMW battery terminals cut off and cheap- strip the wire and clamp the bare ends- terminals installed. We redid all the battery wiring with new terminals, with studs, and I soldered nice copper lugs to the abused wiring. Now the headlights are running at FULL output, even at idle.
 
Last edited:
Get your ecm flashed and see if that helps i believe the regulator is built inside the ecm on that one and since you tried a new battery and alternator that may be the issue. Write back and tell us if that is the issue. The re flash will help other things also especially if it was never done.

How many miles and is it the durable 3.3 ?
 
Boy you really have it covered in the diagnosis department. Before I read your list I said to myself, corroded ground wires all the way.
I would add a ground from the engine block to the frame/subframe/body if you don't have one already.
I'd also consider a custom built alternator (but beware, some ebay alternators only put out high power at high rpm) and/or a pulley change. Lots of fleet trucks have dual alternators. I'm guessing brother, I feel for you chasing this down.
Like others have said too, new proper sized wiring in the critical areas can work wonders.
You have verified your gauges both internal and external you are using for testing, right?
Again, lots of good ideas from others. Good luck.
 
If you've had this problem the entire time you have owned the van, you have to seriously consider it may be normal behaviour.

You should know that no automotive electrical system is designed to operate all possible electric loads simultaneously. If you have a robust charging system it will operate most systems expected in normal driving st a road RPM.

There are teo types of voltage regulators inn common use. Note that I am not referring to "one wire" vs "three wire" types.

One type will send a voltage based on alternator RPM, and uses the battery to provide power until the alternator output exceeds the battery voltage.

The other type runs off the battery alone until the regulator is "flashed" at a certain alternator RPM.(typically around 1800 engine RPM). Even if the alternator is capable of charging the battery, it will not do so until the throtle is "blipped " at or above the cut-in RPM.

Once "flashed" the alternator will output a voltage until the motor is shut down and before it is flashed there will be no alternator output even if the engine runs for hours below approx 1800 RPM.

So the first thing to do is find out what type regulator your van uses. You can determine this by a little experimentation with a right foot and a voltage measuring device.

It does sound like you have the former type, though.

Regardless, the solution is an aftermarket alternator wih usable output at 800 RPM.

Alternators typically can run about 10,000 RPM. If you spend money you can get one with usable output at perhaps 1250 RPM. If your stock redline was 5,000 RPM there will be a 2:1 pulley ratio so that 800 engine RPM = 1600 alternator RPM.

You can determine the low RPM output you desire by adding the amperage of the systems you want to run simultaneously at idle. Then get an alternator with that capacity at the appropriate alternator RPM based on your pulley ratio.

A "quick and dirty" guesstimate is if your alternator will output 60A at engine idle, it will simultaneously run normal lighting, two electric engine fans (one for A/C), a heater / defroster fan, and a modest car stereo, and wipers.
 
Originally Posted By: CT8
New battery terminals? How are they attached to the cables? Those are not the best choice for cables yep they are temporary though that might be the problem.at are you using to check the volts? Is the fan belt slipping? Could the pulley on the alternator be the wrong size? And the basic stupid question have you tried to find another like van to compare the volts?


Wow, I didn't know that there was such a thing as temporary cables. Thanks guys. I figure that this isn't the problem though as I have these on another vehicle or 2 with no issues.

I am using a VOM across the battery terminals, although I use my radar detector for more dynamic monitoring (which does obviously read lower).

I am wondering about the pulley myself and starting to wonder if this might be normal.

http://dodgeforum.com/forum/dodge-ram-van/310745-voltage-drop-at-idle.html

Not stupid questions at all.

Lastly, I'd love to try and find another van and identify whether or not this is normal. The rare AWD of this vehicle uses a different PCM, so I wouldn't be 100% confident in comparing it against another FWD van, but pretty confident.
 
Originally Posted By: HerrStig
Originally Posted By: CT8
New battery terminals? How are they attached to the cables? Those are not the best choice for cables yep they are temporary though that might be the problem.at are you using to check the volts? Is the fan belt slipping? Could the pulley on the alternator be the wrong size? And the basic stupid question have you tried to find another like van to compare the volts?
Quick release... how often do you use that "feature". Get some terminals with a nice big threaded stud and nut for the cable connection and attach a good quality copper lug to the cable, place on the stud and tighten. BTW, you've had THREE alternators? By this time I'd be looking at car audio vendors for a "high output" alternator rather than another stock one. 150 amps would be nice. You can't get blood out of an stone. MY son's restoring a BMW 633CSI> A prior mo-ron of an owner had the BMW battery terminals cut off and cheap- strip the wire and clamp the bare ends- terminals installed. We redid all the battery wiring with new terminals, with studs, and I soldered nice copper lugs to the abused wiring. Now the headlights are running at FULL output, even at idle.


Thanks for the tips. I like the quick removal feature. It helps since something is always going wrong with one of my vehicles as they age. It's nice to not put as much wear and tear on the terminal nuts and have them looking like garbage in no time.

Thanks for explaining how to put a permanent one there....again I had no idea about that.
 
Originally Posted By: crazyoildude
Get your ecm flashed and see if that helps i believe the regulator is built inside the ecm on that one and since you tried a new battery and alternator that may be the issue. Write back and tell us if that is the issue. The re flash will help other things also especially if it was never done.

How many miles and is it the durable 3.3 ?


I am thinking about it. Yes, the regulator is internal and I have run an external regulator by bypassing the internal regulator to no avail. This is the 3.8.

It has 160k miles on it and has behaved like this since I got it with 135k miles.

I might try to reflash it, but no sure that would assist after bypassing the regulator and running an external one already as a test.
 
Originally Posted By: c502cid
Boy you really have it covered in the diagnosis department. Before I read your list I said to myself, corroded ground wires all the way.
I would add a ground from the engine block to the frame/subframe/body if you don't have one already.
I'd also consider a custom built alternator (but beware, some ebay alternators only put out high power at high rpm) and/or a pulley change. Lots of fleet trucks have dual alternators. I'm guessing brother, I feel for you chasing this down.
Like others have said too, new proper sized wiring in the critical areas can work wonders.
You have verified your gauges both internal and external you are using for testing, right?
Again, lots of good ideas from others. Good luck.


Thank you. I ended up answering a lot of your questions in previous posts. Really wondering about the pulley size at this point although the original alternator did the same and everyone claims that the original Denso is easily good for 150k miles.
 
Originally Posted By: Johnny2Bad
If you've had this problem the entire time you have owned the van, you have to seriously consider it may be normal behaviour.

You should know that no automotive electrical system is designed to operate all possible electric loads simultaneously. If you have a robust charging system it will operate most systems expected in normal driving st a road RPM.

There are teo types of voltage regulators inn common use. Note that I am not referring to "one wire" vs "three wire" types.

One type will send a voltage based on alternator RPM, and uses the battery to provide power until the alternator output exceeds the battery voltage.

The other type runs off the battery alone until the regulator is "flashed" at a certain alternator RPM.(typically around 1800 engine RPM). Even if the alternator is capable of charging the battery, it will not do so until the throtle is "blipped " at or above the cut-in RPM.

Once "flashed" the alternator will output a voltage until the motor is shut down and before it is flashed there will be no alternator output even if the engine runs for hours below approx 1800 RPM.

So the first thing to do is find out what type regulator your van uses. You can determine this by a little experimentation with a right foot and a voltage measuring device.

It does sound like you have the former type, though.

Regardless, the solution is an aftermarket alternator wih usable output at 800 RPM.

Alternators typically can run about 10,000 RPM. If you spend money you can get one with usable output at perhaps 1250 RPM. If your stock redline was 5,000 RPM there will be a 2:1 pulley ratio so that 800 engine RPM = 1600 alternator RPM.

You can determine the low RPM output you desire by adding the amperage of the systems you want to run simultaneously at idle. Then get an alternator with that capacity at the appropriate alternator RPM based on your pulley ratio.

A "quick and dirty" guesstimate is if your alternator will output 60A at engine idle, it will simultaneously run normal lighting, two electric engine fans (one for A/C), a heater / defroster fan, and a modest car stereo, and wipers.



Wow, your point seems to be supported by the below URL even though it is not the same van, but there is obviously a nexus.

http://dodgeforum.com/forum/dodge-ram-van/310745-voltage-drop-at-idle.html

However, again, all of my other vehicles put out better voltage at idle....or do they?

I can't remember....but comfort is not the foremost thing on my mind in say my GVR-4. I don't have the A/C blasting all the time at full force, nor do I have the headlights on etc....but the car is loaded with aftermarket gauges....still, they don't pull the same current as the accessories that you would expect on what is often used as a family vehicle....like a minivan.
 
This thread has peaked my interest:

1) Why are there temporary battery terminals at all?

2) Why are there pulleys put onto alternators that clearly don't support charging at idle?

Thanks
 
I had a 2000 town and country with all sorts of electrical issues. Run the engine and wiggle the main harness. Listen for changes in load. Pull the hvac fan speed switch connector.... all sorts of power goes through that and it's a weak spot and can char. Find your battery temp sensor and make sure it's not all corroded.
 
Originally Posted By: eljefino
I had a 2000 town and country with all sorts of electrical issues. Run the engine and wiggle the main harness. Listen for changes in load. Pull the hvac fan speed switch connector.... all sorts of power goes through that and it's a weak spot and can char. Find your battery temp sensor and make sure it's not all corroded.


Battery temperature sensor is internal to the PCM. I'll try the other stuff out.
 
Status
Not open for further replies.
Back
Top