Archived Help Me Charge Again

[blubyu]

01 a\t 4wd alternator is not putting out any current. Two new alternators, two PCM. And still no output. Have check grounds and all fuses, plus relay any help please. :--)

 

[Missouri Mule]

Try checking battery temp sensor/wires/ connectors under driver's side battery tray.

If the PCM is not getting a signal (tempature reading) from battery temp sensor it wil not tell alternator to charge.

On the 96 the ASD (automatic shut down) relay sends voltage reading to PCM.

On 96 the engine speed sensor turns on asd relay I believe, the crank speed sensor mite do this as well ( usually when engine speed sensor/connector was the problem the tach would be acting up also).

 

[SRubenstein]

Are you getting an RPM reading when the truck is running. Last one I worked on with this problem ended up having a bad crank sensor (broken wire). With the DRB scan tool you can test the pcm and wiring by commanding the alternator to full field and watching your voltage increase. Good luck.

 

[blubyu]

Temp sensor checks ok. 5 volts and no shorted wire. Tach works great. ASD relays comes on when the key is in run pos. for a few seconds, then when the motor is running it is not on, Can the ECM cause any of this?

 

[blubyu]

Dealer said to have checked PCM, says it is OK. He says it is the wiring. I have checked every wire for a short. They check fine.

 

[Missouri Mule]

Don't know what turns the asd relay on or off or if it has anything to do with voltage reading on 01(They mite of changed things around with the 24 valves).

Someone with a 01 service manual should be able to tell you.

 

[SRubenstein]

Reading through your last post I noticed you said your Batt temp sensor was 5 volts. This would indicate a shorted sensor and tell the PCM that your battery is overheating. You should have a reading in the . 5- 2. 5 volt range. The pcm sends out a 5 volt signal that gets reduced by the variable resistor (temp sensor). This should have also triggered off a DTC P1492 Ambiant Battery Temp too High. Are you using a DRB to monitor your Batt temp sensor? If you have this scan tool you can try commanding the alternator on through the system tests menu. The green field wire should pulse 12v+ every 1. 4 seconds when the pcm tries to turn the alternator on. I also happened to notice that there is a second fuse involved w/ the charging system. It is Fuse #3 (20 amp) in the Power distribution center. Along of course w/ the 140Amp generator fuse also in the PDC. Keep in mind your charging system voltage will be low for the first few minutes if the vehicle is cold (due to the amperage pull from the grid heater). Let me know if you need a wiring diagram. We have Mitchells and Alldata at my shop and I'd be happy to give you any info you need. Good luck. Scott

 

[Missouri Mule]

Are you receiving 5 volts at battery temp sensor or sending 5 volts?

As SRubenstein stated sending 5 volts is not good.

 

[Grizly]

O. K. guys seems like other fella got his fixed or has not returned yet, I have same problem but have not tested ecm yet, thinking of ordering 1 monday but wha else could I check? not stealing thread but in need of same kinda help.

 

[Missouri Mule]

Grizly, You should have battery temp sensor under drivers side battery tray also. Check wires and connectors.

Don't know if PCM(EVR located inside of pcm on 96's monitor line voltage,battery temp and regulates the alternator out put ) or ECM is in control of alternator charge on 24 valve engines.

 

[Grizly]

Yes have removed batt to look at temp sensor and disconected sprayed electrical cleaner on connections but all looks good and mine is a 24 valve 2nd gen motor so was thinking ecm is what is bad? only thing I have problem with is the charging system? truck runs fine til I get down to 7 volts or so which was only 1 time...

 

[Grizly]

acts like bad alt but when I took it off and went to zone to test ,it passed no problems found???

 

[SRubenstein]

Not to be rude but there is a little more involved than just looking at the temp sensor. Do you own a DVOM or a test light? Here is the basics of what your looking for. The blk w/ gry or black (thick wire) which goes on the stud on the back of the alternator should be a constant 12 volts at all times (key off or on). The green wire on the plug should be a 12v signal from the pcm commanding the alternator to turn on (when running). The blue wire on the plug is the output signal from the alternator which reports current voltage coming out of the alterantor. The ground is from the alternator bracket which of course is attatched to the block (be sure to check this for a good ground, seen problems with it before). The pcm has to look at different inputs before it will turn on the alternator. The 2 main items are battery temp and rpm's. I would hate to see you throw a pcm in this without at least testing your input/ outputs. With the proper scan tool you can command the pcm to turn on the alternator field and start charging. don't get me wrong it could be a pcm but thats a pricey part to be testing with. The battery temp sensor shouldn't be reading above 3 volts on the pnk/ yel wire wire when the sensor is plugged in. the blk/ blue wire at the sensor is the ground for the sensor. The resistance in the sensor limit the amount of voltage the pcm sees and therfore determines battery temp. Let us know how you make out.

 

[SRubenstein]

Any update from either one of you guys w/ your charging system problems. I'd like to know how you made out.

 

[Grizly]

Sorry guys had to make up for lost work time from this problem: update= after being in dodge for 2 1/2 days and down for weekend before total of 5 days truck is now charging after I went to a zone and exchanged alt for new it started working again... makes me mad that other a zone tested and said was good alt so I never checked up on it again: dodge charged 150. 00 labor 1 night motel = 60. 00 / batter charger from sears 38. 00 / down time = 600. 00 that hurt ..... lesson learned YES

 

[blubyu]

Sorry took so long. The ECM was it. The battery sensor only controls about one to two volts + or -. The ECM has to tell the PCM the motor is running, so it will then kick in the asd relay, tell the alt to charge, and kick in the transmission relay. After 6, yes 6 trips to the dealer I figured this out. Have service man. on 01, spare PCM, wiring harness for parts, if I can help someone else. Again THANK EVERYONE for the help. Oo. Oo. Oo. Oo.