Engine/Transmission (1994 - 1998) Charging Problem

[SLangegger]

I recently had a charging issue with my 95. The gauge would read low and the CEL would come on. If I tapped on the alt, the gauge would come up and everything would be fine. I figured it was the alt. so I replaced it. Now the gauge reads low and there is no CEL. Tapping on the alt. doesn't fix the problem anymore. I tested the volts on the batteries, they both read above 12 when disconnected from the truck. Im wondering if its the PCM? Any ideas?



Thanks

Steve

 

[Howard Durand]

What does the voltage read when the engine is running? If it stays at 12 volts or less, I would guess the regulator may have failed.

The voltage regulator is a part of the PCM but if that is the only problem you have, check the forum for voltage regulators. Several members have installed external regulators which work quite well.

 

[SLangegger]

Howard,



It said around 11 volts. I cant remember the exact reading. I searched and found something about a large 150 amp fuse that could also be the problem. Do you have any information about that fuse and its location?

 

[Howard Durand]

That would be the fuse in the line that feeds the alternator output into the Power Distribution Center. (fuse box under the hood on driver's side fender)

My 94 has a 120 amp fuse. Yours is probably the same.

You should be able to see it when you take the cover off of the fuse box.

It makes up the connection between the incoming alternator wire and the fuse box. It is actually bolted in place. You can easily see if it is blown or not.



11 volts is too low for batteries, especially when the engine is running. Should be around 14 volts unless there is a heavy load switched on such as the intake air heaters.



Hope this helps.



Howard

 

[Missouri Mule]

Check your battery temp sensor underneath the driver's side battery tray.

Battery temp sensor/connector/wires.

11 volts is to low if engine is running or not. Mite need to change batteries.

 

[Vaughn MacKenzie]

Batt temp sensors on a 12-valve??

 

[Bill Lins]

Yup- on the driver's side- just forward of center in the floor of the battery tray.

 

[Howard Durand]

As the Missouri Mule states, you may need to replace the batteries.

Get them fully charged and have them load tested.

Good batteries make a difference, I have a set of Optima red top batteries that are unbelievable, they have been on the truck for 6 years. Just had them load tested and they are still as good as ever.

 

[K5IP]

First question,

Does your Tach work?

The PCM requires an input from the tach (to indicate that the engine is running) before it will initiate a charge condition (by providing a field current).

I would have bet on a bad alternator from the conditions you first described (tapping fixed it), and probably brushes at that. Perhaps you got a bad replacement.

As previously mentioned, your battery voltage should be about 12Vdc, engine not running. This should increase about 2Vdc when the alternator is charging.

PM me if you like and I will walk you through a troubleshooting proceedure. I have a Dodge 95 manual with wire colors so I can lead you to the right wires and the voltages you should have.

Rog

 

[SLangegger]

K5Ip,



My tach works fine. I will try new batteries and check the fuses. If that dosent fix it, Ill shoot you a PM.



Thanks for all the replies

Steve

 

[Skydiver]

When my alt. ( or gen ) light came on the problem was the grid heater solenoid sticking closed. After 3 minutes the PCM shuts down the charging system. I disconnected 1 wire from each solenoid. That is until the temp dropps below 25 F.

Smokes a little more when below 50 F

Tim

 

[Missouri Mule]

Have your batteries load tested.