1998 Dodge Cummins Ram - Bad Batteries and Dead Dash Lights

G'day, I think you're correct in thinking the battery is being drained through the alternator. However, does your alternator have an integrated brush holder/regulator as the Bosch alternators do? If so, the most common cause of failure of these things is the brush holder/regulator. I've been able to find these on Ebay, (new) for about AU$36 plus post.

It sounds like you have no output from the alternator at all. Maybe run a multimeter over the alternator and see if any shorts appear. Does the charging light wire have voltage when the ignition is on? If no voltage, measure the resistance between the charge light wire on the alternator and the battery positive with the ignition ON. If there is more than about 20 ohms look for a fault in that circuit, less than 2 ohms, a short. Also measure the resistance from the alt positive to earth with the battery disconnected and ignition OFF. If R < 6 , look for a short.

Of course you could also try an Alternator from the Wreckers or another car.

Good luck

Royce

I will look for the holder/regulator. That would be great if all I had to do was replace that. Forgive me for asking this, but what is the charging light wire? Is it what we call the hot wire or positive wire? I'll tear into that today and check the things you mentioned. Now I know where to go with it.

Is Caboolshit actually Caboolture? That cracked me up and I had to ask.

Phil

Brushes wear, causing open circuits.

A drain is usually a shorted regulator, or rectifier.

Often the alternator will feel slightly warm, from the current draw.

Check when the vehicle has been sitting.

If all the warning lights are on (bulb check, as if you are cranking) then you have no alternator output.

Commonly, the brushes are worn, if you "smack" the alternator, sometimes they will regain contact. If you do this with the engine idling, you will hear the alternator kick in. This is temporary, replace the brushes, or have it rebuilt, or exchanged for a reman.

You stated that you could get it started but it would then die. would it die as soon as you let the key go back to the run position. If this is what is happening then you may have a bad ignition switch and will have to be replaced. If it is the switch then when you turn it to run position then you would not have any accessories that would function.

The item in the diagram below is of the power distribution center that is located under hood on top of the drivers side fender well. The item marked GEN is a 140 amp fuse and may be blown. before you do a lot of testing you need to disconnect the negative terminal from the battery as the alt. charging rate is controlled by the PCM. The Electronic Voltage Regulator (EVR) is not a separate component. It is actually a voltage regulating circuit located within the Powertrain Control Module (PCM). The EVR is not serviced separately. If replacement is necessary, the PCM must be replaced. The amount of DC current produced by the generator is controlled by EVR circuitry contained within the PCM. This circuitry is connected in series with the generators second rotor field terminal and its ground. Voltage is regulated by cycling the ground path to control the strength of the rotor magnetic field. The EVR circuitry monitors system line voltage and battery temperature. It then compensates and regulates generator current output accordingly. The battery temperature sensor 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. Provides a signal to the PCM corresponding to the battery temperature.Battery temp. is sensed by sensor in the bottom of the battery tray.

The more info that you can supply as to the operation of indicator lights on the dash are other accessories such as radio with the key in acc./off/run/start position will let me get you closer to the problem and a reasonable solution.

Thank you Jim! Great explanation of the PCM and EVR. I didn't see your reply until today, so I had already taken the alternator off the truck and had it tested. It tested good, so at least I know the alternator is working.

One of our employees mentioned that the truck wouldn't start when he put the charger on "50 amp Start". I told him that it wasn't meant for that and read to him the info on the charger that it is not to be used to jump start the engine. Another employee admitted that he tapped the opposite leads of the charger on the battery posts for a spark to see if they were still alive. Again, that alarmed me and I told him that he could damage the electronics doing that. Since both brand new batteries kept going dead, I took them out of the truck and put a trickle charger on them. That didn't bring them up to full charge, so I took the batteries to O'Reilly's and they fully charged them for me, so I know that the batteries are okay. I don't know if they killed the charger crossing the leads, but it wasn't charging anymore. Now I have a new charger.

I will check the fuse to see if it is blown and get back to you. If the fuse is not blown, should I hook the batteries back up and try the switch again?

Thanks

Phil

There is a self test available for the cluster that will actuate all the gauges at their calibration points. The test will not run if the cluster sees engine RPM or vehicle speed. This test will light all CCD controlled lamps for verification of lamp operation. It also forces the odometer Vacuum Fluorescent Display (VFD) to perform a segment check. The self test routine can be entered by pushing and holding the trip reset button while rotating the ignition key from the "OFF" to the "ON" position. When the word "chec" appears release the knob and the test will continue. I have been unable to find a definite answer as to why the odometer is flashing but if the self test will not run then probably the instrument cluster will have to be replaced. If you can get a scanner to read any diagnostic codes that are stored it would probably give a hint as what caused these problems. Since the dash lights are not functioning then you can't use the onboard diagnostics but you can try to by turning the ignition key off/on/off/on/off/on and if it does function then it will flash the codes with the check engine light and if you would post them I may be able to get a closer reason for this electrical problem. If it won't so the codes then most parts stores will read the codes for you and some even loan the scanners I know that Auto zone does with a deposit and I imagine O'Riellys also do but I'm not sure. Hope this helps.

Use a DVOM and check the amps draw between the Battery ground wire disconnected and the battery negative terminal. You have to wait until all the under dash lights shut off.The draw isn't much usually less than enough to light a 12 volt test light. Unhook the alternator if you have a big draw if it stops repair it or take it to an alternator shop. You have to keep checking until you find the problem like a sticking relay light staying on or other problem. You can use your meter and check the voltage at the ignition switch. Find the problem first.

I forgot to mention that we were able to get the truck running and test drove it a couple of times. The dash lights never came on, the warning lights stayed on, the odometer continued to flash and the headlights stayed dim. After driving, we shut off the engine and couldn't start it again without jumpstarting.

Just saw the last post and have a simple test that will tell you if the charging circuit is working since you know that the alt is functioning. take a voltmeter and hook it up to the battery terminals and see how much voltage you have in the batteries then start the truck and check the voltage again it should be reading between 13.5 and 14.5 volts. Check this not only at idle but also at around 2000-2500 RPMs if the voltage is correct then the voltage regulator circuit is functioning properly but I will bet that it isn't because the batteries drained after driving it for a short period of time. If you will post the results then I will try to point you in the correct direction to solve your problems.