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Discussion Starter · #1 ·
the battery light is on all of the time that the car is running, but the alt is working. it is putting out 14.4 volts with all
accessories turned on, which is good. just don't understand why the battery light is on.
I have had one shop tell me that is in the pcm and that it will need to be replaced. could this be right?
 

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1st thing.... Year, make, model and perhaps mileage, (I eventually put my info in my signature/profile because I regularly forget)

Is this an on going fault or something that just started?

Is the check engine light on? Has it been on and you have been ignoring it for quite some time? Just curious


Sometimes and I'll use fuel injectors as the example, the PCM grounds each fuel injector to make it spritz. The fuel injector have a constant on dc power and the PCM completes the path to ground as timed to when the intake valve opens.
It may be that with the battery light indicator too. Perhaps the wire that goes to the PCM has a short to ground and thus the light thinks the PCM is grounding it due to a battery fault. I don't know this to be fact but just thinking out loud here. [almost certainly someone will be along soonly to explain that I may be sadly mistaken and don't know what I am talking about :]

Got jumper cables and another vehicle handy? connect (+) pos to pos and ground engine block to engine block. Then start and with just your van running, disconnect the negative of your battery and you van will be running on the other battery.
Did the light situation change?
My thought (again based on your unknown year make model) perhaps the genius computer can detect a batteries internal resistance?

There is one more thing and it is when an alternator diode leaks ac voltage onto the electrical system, it can cause all sorts of PCM anomalies. I think it is called ac ripple. google that and basically you test for A/C volts with you multi meter with engine running.
 

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1st thing.... Year, make, model and perhaps mileage, (I eventually put my info in my signature/profile because I regularly forget)

Is this an on going fault or something that just started?

Is the check engine light on? Has it been on and you have been ignoring it for quite some time? Just curious


Sometimes and I'll use fuel injectors as the example, the PCM grounds each fuel injector to make it spritz. The fuel injector have a constant on dc power and the PCM completes the path to ground as timed to when the intake valve opens.
It may be that with the battery light indicator too. Perhaps the wire that goes to the PCM has a short to ground and thus the light thinks the PCM is grounding it due to a battery fault. I don't know this to be fact but just thinking out loud here. [almost certainly someone will be along soonly to explain that I may be sadly mistaken and don't know what I am talking about :]

Got jumper cables and another vehicle handy? connect (+) pos to pos and ground engine block to engine block. Then start and with just your van running, disconnect the negative of your battery and you van will be running on the other battery.
Did the light situation change?
My thought (again based on your unknown year make model) perhaps the genius computer can detect a batteries internal resistance?

There is one more thing and it is when an alternator diode leaks ac voltage onto the electrical system, it can cause all sorts of PCM anomalies. I think it is called ac ripple. google that and basically you test for A/C volts with you multi meter with engine running.
Please share what you find and how you fix it.

It is your feedback that makes this forum work. If you don't give back you final solution, the next guy will find just another person who has a similar problem and then there is no answer.

Cheers and good luck!
 

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Discussion Starter · #4 ·
the battery light is on all of the time that the car is running, but the alt is working. it is putting out 14.4 volts with all
accessories turned on, which is good. just don't understand why the battery light is on.
I have had one shop tell me that is in the pcm and that it will need to be replaced. could this be right?
it is a 2006 Chrysler town & country milage 187000 the check engine light is not on. this just started about 4 weeks ago. at first the battery light would come after driving a ways. I have had the alt replaced, replaced alt belt & tensioner. I have had the alt. tested it peak amps is 165 amps, diodes check ok. at first when the battery light came on you could shut off the car and restart it the light would be off until you drove it a ways. I am lost for what is wrong with this car
 

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Your battery light is on but your battery is checking out at 12.6 volts or more, engine not running?

How old is the battery? Has it been run down much? Keeps its charge for several days when vehicle isn't being used?

What fault codes are being stored?

Is the Shop, that told you it was a pcm, a Brake Shop or an Electrical Shop? Their qualifications, or lack of, may cost you needlessly.

Disconnect the negative battery cable and touch it against the positive terminal, then reconnect, to see if the problem corrects itself. That process reboots the computer.
 
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Your battery light is on but your battery is checking out at 12.6 volts or more, engine not running?

How old is the battery? Has it been run down much? Keeps its charge for several days when vehicle isn't being used?
Good point, where are you located and what is the climate been of late.

Sear and others sell five year batteries and some times they last five years but most of the time they do not.
The marketing scam is that they sold you a percentage of your next battery 'up front' and this way you return to buy another die harder for your $36.58 prorata credit' ... thus buying into your next battery once again.'

I seem to get good batteries at Home Depot under the Exide brand name and what is cool about HD is that they are not a battery store so they don't have testing and such. As long as you have the receipt and it is within the time frame, you get a replacement.

*Take the batteries from the back of the rack, they are newer...

I told you these guys at the Mopar Minivan Garage rock!
 

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Discussion Starter · #8 ·
Good point, where are you located and what is the climate been of late.

Sear and others sell five year batteries and some times they last five years but most of the time they do not.
The marketing scam is that they sold you a percentage of your next battery 'up front' and this way you return to buy another die harder for your $36.58 prorata credit' ... thus buying into your next battery once again.'

I seem to get good batteries at Home Depot under the Exide brand name and what is cool about HD is that they are not a battery store so they don't have testing and such. As long as you have the receipt and it is within the time frame, you get a replacement.

*Take the batteries from the back of the rack, they are newer...

I told you these guys at the Mopar Minivan Garage rock!
the battery is about 6 months old. I have tested the battery, & alt, & starter on a bear arbst tester. the battery test ok
the alt. test ok, and the starter test ok. the weather has been warm & dry. temp 93
I have a volt meter in the cab with me. with the car running at idle and in park the voltage is 14.40. if i slowly increase
the rpm,s and watch the volt gauge and tach this is what it does. 14.40 volts up to 2500 rpm then it drops to 12.6 volts
if you keep it at that rpm or higher it will not charge. when ypu let the rpm back down it will start chargeing again at about 1800 rpms. when ther battery lights comes on it will stay on even if it is charging untill you turn car off and start it up. two new alt. new belt and teasioner.
 

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the battery is about 6 months old. I have tested the battery, & alt, & starter on a bear arbst tester. the battery test ok
the alt. test ok, and the starter test ok. the weather has been warm & dry. temp 93
I have a volt meter in the cab with me. with the car running at idle and in park the voltage is 14.40. if i slowly increase
the rpm,s and watch the volt gauge and tach this is what it does. 14.40 volts up to 2500 rpm then it drops to 12.6 volts
if you keep it at that rpm or higher it will not charge. when ypu let the rpm back down it will start chargeing again at about 1800 rpms. when ther battery lights comes on it will stay on even if it is charging untill you turn car off and start it up. two new alt. new belt and teasioner.
I don't have a solution but I have to say that what you disclosed in this post is very different from what is in your initial post and in the title of this thread. In this case it is pretty obvious that the battery light is coming on because the alternator stops charging at some point. The problem is not that the light is on despite the charging system working properly as the thread tile and initial post both imply. The charging system is clearly not working properly.

I don't understand why it is so difficult for people who are asking for help with their vehicles to fully explain what they are really experiencing. The information has to be extracted as if it is top secret data or something. This is almost as bad as people who come to this forum seeking a solution to some issue and then never follow up with what resolved their problem. They both waste the time of people who are trying to help.
 

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have a volt meter in the cab with me. with the car running at idle and in park the voltage is 14.40. if i slowly increase
the rpm,s and watch the volt gauge and tach this is what it does. 14.40 volts up to 2500 rpm then it drops to 12.6 volts
if you keep it at that rpm or higher it will not charge. when ypu let the rpm back down it will start chargeing again at about 1800 rpms. when ther battery lights comes on it will stay on even if it is charging untill you turn car off and start it up. two new alt. new belt and teasioner.
Is your van equipped with a battery temp sensor in the battery tray? is it plugged in and functional?
It should not be charging the battery at 14.4 bolts at 93*F - the system should lower the voltage to prevent boiling electrolyte...

FSM said:
The amount of DC current produced by the gener- ator is controlled by the EVR (field control) circuitry contained within the PCM. This circuitry is con- nected in series with the second rotor field terminal and ground. An Ambient air temperature sensor is used to cal- culate the temperature near the battery. This tem- perature data, along with data from monitored line voltage (battery voltage sense circuit), is used by the PCM to vary the battery charging rate. This is done by cycling the ground path to control the strength of the rotor magnetic field. The PCM then compensates and regulates generator current output accordingly to maintain system voltage at the targeted system voltage based on battery temperature.
...
The Charging system “Battery” light indicates problems with the charging system (voltage too high/ low, generator failure, etc.). If an extreme condition is indicated, the lamp will be illuminated. The signal to activate the lamp is sent via the PCI bus circuits. The lamp is located on the instrument panel. Refer to the Instrument Cluster section for additional infor- mation. The PCM uses the ambient air temperature sensor to control the charge system voltage. This tempera- ture, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. The system voltage is higher at cold temperatures and is gradually reduced as the calculated battery temperature increases. The ambient temperature sensor is used to control the battery voltage based upon ambient temperature (approximation of battery temperature). The PCM maintains the optimal output of the generator by monitoring battery voltage and controlling it to a range of 13.5 - 14.7 volts based on battery tempera- ture.
 

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Discussion Starter · #11 ·
Is your van equipped with a battery temp sensor in the battery tray? is it plugged in and functional?
It should not be charging the battery at 14.4 bolts at 93*F - the system should lower the voltage to prevent boiling electrolyte...
thanks for the info I do not think the car has a battery temp in the battery tray, if it does I have missed it. where in the battery tray should it be what does it look like?
 

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thanks for the info I do not think the car has a battery temp in the battery tray, if it does I have missed it. where in the battery tray should it be what does it look like?
There should be a round plug about the size of a dollar coin (same color as the tray) towards the passenger side and rear of the battery tray. It pops up about an eighth of an inch when you remove the battery, the wires are underneath and are easily missed if you don't look for them.
Supposedly it was done away with in later 4th gen, so yours may not have one. If that's the case, check the ambient temp sensor in front of the radiator. A malfunctioning IAT should set off a DTC and MIL, but ambient temp sensor probably does not...
 

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Discussion Starter · #13 ·
There should be a round plug about the size of a dollar coin (same color as the tray) towards the passenger side and rear of the battery tray. It pops up about an eighth of an inch when you remove the battery, the wires are underneath and are easily missed if you don't look for them.
Supposedly it was done away with in later 4th gen, so yours may not have one. If that's the case, check the ambient temp sensor in front of the radiator. A malfunctioning IAT should set off a DTC and MIL, but ambient temp sensor probably does not...
there is nothing like that in the battery tray, will look for the ambient temp sensor tomorrow you say it is in front of the ratator. that would put it behind the grill, right?
this problem is changing, it was where when you first started it up the battery light would be out, now the battery light is on all time. what gives? it has no codes stored in it, the check engine light is working and is out. I just got done doing a voltage drop test on both battery cables, they checked ok.
 

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will look for the ambient temp sensor tomorrow you say it is in front of the ratator. that would put it behind the grill, right?
Yes, there should be a bracket bolted to lower radiator support with the sensor maybe inch and a half in front of the radiator bottom under the grill / facia.
If you have an overhead console with EVIC or Trip computer, it should display temp reading from this sensor...

It can also be that the alternator you got is a rebuilt that didn't have collator brushes replaced and at higher rpms the brushes are not making good enough contact to maintain field winding current. You can try to test it with an ammeter on the field connector and revving up the engine with accessories on...

If all else fails, it's possible to get an external voltage regulator to avoid having to replace the pcm.
 
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