my truck stopped charging last night ,,its done this once before but the alternator checks out fine,,,my uncle shook the wires coming from the alternator down the side of the engine and said he seen a spark,,but i couldnt find any bare spots after that the truck has been charging fine until last night,,,i would like to know if anyone else has had this problem and if theres any way to fix it,,is it a common problem for our first gens,,any help will be greatly appreciated,,,,,,,

 

External regulator, or PCM? Any other symptoms?

 

well the hand will still work but it stays down on the first mark ,,but if you use the head lights it will drain the battery,,,,the regulater was getting ready to go out i think cause the needle was bouncing ,,,but if it was the regulator wouldnt it over charge....thanks for helping ,,,,,

 

Regulator can either over or under charge. What you need to do is disconnect the regulator and full field the alternator. If it charges hard then, it's the regulator.

It is possible for the belt to slip on the pulley enough that the alternator won't charge. Full fielding will make that evident (smokey) also.

To full field the alternator, disconnect the regulator connector, then connect one field terminal on the alternator to ground, the other to 12 V. (temporarily) Polarity doesn't matter.

The reason I asked if it was an external regulator or the PCM is that the PCM regulator rarely fails, but must see input from the crank position sensor to turn on.

 

ok someone told me to ground the field terminal closest to the top of the alternator,,,,it maxed out the charging hand like that,,,,but i didnt disconnect the voltage regulator...do you think i might have hurt something by doing that,,,i only touched it to ground about 3 times and each time the hand would max out,,,,,ive checked all my wiring and every thing looks good,,,my friend is gone now to autozone and hes gonna have them check out my alternator,,where can i get a good regulator at,,not these dang chinese ones,,,,,

 

Shouldn't hurt anything. Why, when you proved your alternator is OK are you taking it to Autozone? It appears the regulator is bad. It works by supplying a path to ground on that terminal.

That said, the problem could be grounding at the regulator, and the regulator might be OK.

 

I'm going to give you all my THEORY on why there are so many charging problems on these trucks.

As these trucks age and go beyond a normal truck of this eras life expectancy things occur because of basic design oversights. My theory goes along with the common grounding issues because the common ground between the engine and the cab forms intermittent connections. These intermittent interruptions find there way to the voltage regulator which is a solid state device containing a voltage sensing Integrated circuit and power transfer transistors. When the regulator is saturated with repeated multiple voltage spikes it fails. Replacing the OEM which I believe was a better regulator with a newer aftermarket regulator and not grounding the cab results in either repeated failures or an immediate failure due to the voltage spikes. To me the OEM voltage regulators seem to have a better tolerance to the voltage spikes. Improperly grounding the regulator by using crimp connectors without incorporating anti corrosion grease on the wire ends and at the mounting point and not using a good electrical style tooth lockwasher compounds the issue when the problem recurs. I plan on addressing this specific issue some time in the next few month when I resume work on my crew cab project.

 

Trebor, you nailed it.

Remember, when these trucks were designed, average vehicle life was about 100 - 150k miles. These things are just broken in at that time.

There are several wiring issues in these things. Grounding, heater wiring, not enough circuits (cig lighter and ABS brakes on same fuse for instance), wimpy alternator wiring, etc.

All in all, though, I think they are above average in serviceability.

 

well i sent the alternator to be checked cause my friend was going there anyway,,it tested good,,,could i run a ground wire from the manifold or from the battery itself to one off the regulator bolts ,,and where can i buy a true cummins voltage regulator....im gonna have to get one today,,i hope that solves my problem,,,,if not guys ill be back with more questions,,,,,,

 

There should be a ground strap on it. If not, then run one from there to the cluster ground screw near the battery. While you're at it, make sure the main power wire from the alternator to the battery is in good shape. If it has any terminal on it that looks like it's been hot, replace the whole cable.

 

You can never have too many, or too big, grounds...Mark

 

i had to order the voltage regulator from napa and i told them i wanted the best one they carry ,one intended for a cummins,it was 25 dallors,,,does that sound right?i thought they would be more the name of it is echlin im going to redo my grounds in the morning and try it out hopefully it works,,,i would have done it today but it was raining and ive had the stomach virous,,,,,,,thanks guys for all your input....