Archived 97 12v Charging Problem

[Cooperman]

Three days ago, I went to town (35 mi) with no indication of trouble.



When I tried to start the truck later, the batteries were completely dead. I had a truck hooked up for about half an hour before the charge allowed me to start the truck.



After starting there was no electrical service available at all. No air, no gauges, not able to roll down the windows in 95 degree heat.



Eventually, I got enough charge to start using the electrical services.



I got home, and checked the batteries. DEAD. Replaced them the next day.



Now my GEN light was on, and there was voltage drop after driving the truck for another trip to town. I got a new alternator, and installed it yesterday. Same condition.



The only other problem that is there is the radio is dead. Could be a coincidence, or it could be something related.



Does anyone know if there is a cure here besides a new PCM? If not, does anyone have a line on an affordable PCM? Thanks - Ron Cooper

 

[Grey Wolf]

Did you check all the electrical connections, maybe give them a spray of electrical contact cleaner?



Other than that I've heard Napa has some rebuilt PCM's or theres always here.



Dodge PCM Store

 

[rrl989]

My 98 has a large fuse, like 130 amps at the PDC box. I would see you you have the same and check that fuse first.

 

[Sticks]

^^^^^
Check all your fuses, and IIRC there are a couple of fuseable links (just outside the PDC) in there as well.

 

[p-Bar]

Check your fuses and fusible links as mentioned above 1st. Do you have a VOM volt ohm meter? if so black to ground and red to the large stud on the back of the alternator if you are reading 13. 8 14. 2 or so you are charging go to step 2 put the probes on the batteries if voltage is 12 volt then the wire from the alternator has possibly a blown fusible link as mentioned in a previous post. I assume the PCM has the regulator in it which is probably bad

 

[Skydiver]

When my truck did this it was the grid heater contacts stuck closed. I pulled one small wire from each grid relay, gentle tapped on the grid solenoids to unstick them. Gen light has not came on since. I do not use my grids unless temps fall below 25F.
If the charging current load is too great the pcm shuts down the charging system, so I've been told.

 

[Ramtuf1]

Had the same problem with my 2001 and what it turned out to be was the small two pin weather proof connector at the back of the alternator. Turned out that over time with the cycling of the grid heaters and all that the contacts in the connector stated arcing and then opened the connection so that the alternator would not put out.



I was going to add this to the infamous lock/unlock torque converter thread as I started having issues at the same time as the charging problem, with the torque converter getting reprogrammed and I have made every mod that has come along to date to solve the issue. Replaced the connector on the wire harness at the back of the alternator and all is good again.

 

[GAmes]

Something similar happened to mine right after the warranty had expired. My wife drove it to the grocery store and when she came out the batteries were dead. I was out of state at the time. The dealer replaced both batteries and the preheater relay (I'm assuming it was the fuel heater). It had shorted internally and drained the batteries. There is no telling how long it had been shorted out since my wife has no clue what gauges are for.



I have since found out that if the grid heaters don't turn off the PCM will kick the alternator off line and the gen light will illuminate. Disconnect the relays, restart the engine and the alternator will work normally.

 

[Cooperman]

Thanks GAmes, but that did not work. I have a scanner now, and it indicates the engine is not running !!!!! It does not detect ANY codes. Just gets curiouser, and curiouser.

 

[GAmes]

Thanks GAmes, but that did not work. I have a scanner now, and it indicates the engine is not running !!!!! It does not detect ANY codes. Just gets curiouser, and curiouser.

That is the bad thing (if you believe not having computer controlled everything is bad) about the '97s. Not a lot of codes. Does your tach work? If not, it is likely the engine speed sensor (located above the damper) is bad or one of it's wires is corroded or broken.

 

[Missouri Mule]

Check Engine Speed sensor as GAmes suggest.

ESS activates the Auto Shut Down relay which sends line voltage (readings) to the Electronic Voltage Regulator (EVR) located in the PCM

The Battery Tempature sensor is another component that sends data to the EVR.

With the input from the ASD and BTS the EVR determines Alternator voltage output.

So I believe what I read in the Factory Service Manual the EVR needs both of these inputs or it can not determine Alternator voltage.



Battery Temp sensor located below driver's side battery tray.

ASD relay in PDC.

 

[Cooperman]

<b>Thanks to all you good folks</b>. It is looking like a bad PCM at this point.



It is cheaper now to buy one than to test further at a shop - <b>THEN</b> buy one.



I can run this way until fall or later, since the system stays charged to about 12 volts. I cannot see drops when running all the electrical that I can (lights, air, radio, etc)



Tonight is a test, have to run a long time after dark, with the air on. If it still stays reasonably charged, I will just buy a PCM later on.



Again - Thanks - Ron Cooper