Durango has an intermittent over-charging issue when I am driving. The volt meter will go to 18+ volts and remain there for miles and then go back to normal. Battery is < 6 months old, all grounds are connected and no corrosion, ect.

I assume this is a voltage regulator issue. If i understand the charging operation properly, the PCM tells the alternator to charge the battery to a target value based on measured voltage and temperature. I am wondering if the alternator still has a voltage regulator built in to limit its voltage output or if that is also handled by the PCM?

Basically computer turns alternator output on/off and the voltage output is regulated to 14.4 by the internal regulator in the alternator...

The manual doesn't indicate if there is a regulator in the alternator or not.

This site suggests there is a regulator in the alternator:
http://www.vicic.com.tw/alternators/gvdn11361001.htm
PN for my alternator: 56041324ac

 

There is a regulator inside the alternator built in. This does sound like a voltage regulator issue, however I'd rule out the voltometer giving a false reading by doing your own reading for voltage with a multimeter.

 

Or a bad gauge. The factory gauge set and sending units are not super quality.

If the alt, etc all check out... then plug in a good aftermarket gauge and see what you get.

IndyDurango

 

The PCM tells the alternator to turn on, but the main systems voltage regulator is in the PCM and not the Alternator, however the main output from the alternator should be regulated to stay under 14.4 volts. If it is going over that then the usual issue is the diodes in the alternator.

On the flip side, 99% of all voltage issues is a bad alternator hands down. The PCM voltage regulators are VERY rare to ever go out. Now the alternator, that's a different story. The alternator makes and overage normally to charge the battery as it needs to stay over 12.7 volts and so you have to have at least that just to maintain the battery and not even to charge it under system electric load. This is why the alternator makes around 14-14.4 volts, so it can run the system and also charge the battery as the overage goes into the battery.

Then the PCM gets it's power from the battery and regulates the electrical into the rest of the truck to 12 volts. So it is a simultaneous system working in conjuction. The output of the alternator is what you see on the voltage gauge, not the PCM regulated voltage.

As a rule of thumb, I always replace an alternator and battery together as one usually always puts strain on the other causing them to go out or actually being the cause of why it went out.

+1 Indy! As for a bad gauge? Oh ya! You need to ensure that you actually have an overage of voltage by confirming the output using a multi-meter during the phenomenon.

 

ok, checked it three times on the way to work with the fluke...pulled over and measured the voltage...14.5, 14.6VDC, when the guage went to the pegged state.

So this is likely a bad gauge? How does the gauge work, does it trigger the check engine light in the cluster, and where is it reading voltage? Or is it a computer controlled gauge and the PCM could still be at fault.

Finally, I suppose changing this gauge is a PITA?

Thoughts?

 

@ nmjwolf...
What did you end up doing about your volt spike issue? I have a 2000 Durango, 4.7L V8 and am having the exact same issues. It started when I had a bad crankshaft sensor and needed to replace it. I changed the sensor but immediately had trouble starting. Trouble shot the problem and figured out I had a bad positive cable connection. Replaced the pos. battery cable and all worked well, good starting, ran well for several weeks.
Out of the blue, my volt gauge went up to 18V while highway driving (70+ mph). Once turning the truck off, it would correct the problem. However it intermittently shot back up and would correct itself on it's own or by powering off the vechicle.
I changed the battery since it was only putting out 230 CCA (rated at 810) but day after changing battery, the volt guage shot up to 18V again.

Could this be a bad guage? A bad volt regulator in the alternator? Or a bad volt regulator in the PCM? I've read a lot on the topic and believe it's one of the three (possbily multiple issues). Any suggestion on what to do to trouble shoot the next thing?

 

I would replace the alternator with a new one not a rebuild.


Usually over charging is due to the alternator because the internal electric voltage regulator (rectifier bridge) is damaged or broken. Thus the alternator isn't held at 14.4 volts output maximum.

To verify this, you need to measure the voltage between the battery posts when the overcharging is noticed. So the gauge goes to 18 volts and you get out and measure using a mutli-meter to contest or disprove the phenomenon. If in fact the alternator is over charging then you would then replace it. If in fact it is not overcharging and yet the gauge is measuring that it is you would then have a bad gauge.

If you take out the instrument cluster you can open it and get a old junker one and swap out the gauge and re-install the old one.

Lastly, there is a Battery Sensor under the battery that you can try to replace, but that is usually for under charging of the battery. When the battery gets hot then that means it is getting over charged and therefor will slightly limit the output.

The PCM also adjusts the generator
charge rate through control of the generator
field and provides speed control operation.

BATTERY TEMPERATURE
SENSOR
DESCRIPTION
The Battery Temperature Sensor (BTS) is attached
to the battery tray located under the battery.

OPERATION
The BTS is used to determine the battery temperature
and control battery charging rate. This temperature
data, along with data from monitored line
voltage, is used by the PCM to vary the battery
charging rate. System voltage will be higher at colder
temperatures and is gradually reduced at warmer
temperatures.
The PCM sends 5 volts to the sensor and is
grounded through the sensor return line. As temperature
increases, resistance in the sensor decreases
and the detection voltage at the PCM increases.
The BTS is also used for OBD II diagnostics. Certain
faults and OBD II monitors are either enabled
or disabled, depending upon BTS input (for example,
disable purge and enable Leak Detection Pump
(LDP) and O2 sensor heater tests). Most OBD II
monitors are disabled below 20 degrees F.
REMOVAL
The battery temperature sensor is located under
vehicle battery (Fig. 1) and is attached to a mounting
hole on battery tray.
(1) Remove battery. Refer to 8, Battery for procedures.
(2) Disconnect sensor pigtail harness from engine
wire harness. Sensor pigtail harness is clipped to
vehicle near its electrical connector.
(3) Pry sensor straight up from battery tray
mounting hole.
INSTALLATION
The battery temperature sensor is located under
vehicle battery (Fig. 1) and is attached to a mounting
hole on battery tray.
(1) Feed pigtail harness through hole in top of battery
tray and press sensor into top of battery tray.
(2) Connect pigtail harness.
(3) Install battery. Refer to 8, Battery for procedures.

 

Hello to all, I have 2k 5.2 durango and the volt guage is doing the same over charge while driving. Will correct itself. Replaced the following-altx2, battery, PCM, BST, no fix. Another problem is when I turn things on-blower, lights, turn signal, the volt meter drops down to 8 while idle then rises to 12 when I began to drive. when everything is turn off then charge shows 14. this has gone for a year with no fix.
New problem this winter when cold would not start and run without me holding the pedal down until the engine warmed up. warm weather no issues wih starting.

Any thoughts???????

 

My 2003 dodge durango 4.7 I have replaced the computor 4 new alternators 3 new batteries and tightened all grounds Still charging 17.4-18-6 What can I try next.?
Gauge goes way high and then drops low. At this point you can smell battery .Took it to Chrsysler and they replaced computor and reprogrammed keys. Within 5 miles started acting the same.Wayne

 

Have you checked with a volt meter to see if the dash gauge is right?