I've been getting the "Check Engine" light every now and then lately but it goes away after next start up and I kept forgetting to check until now.

This morning on the way to work I had the headlights on and they were pulsing more than usual (no its not the grid heaters and yes I have extra grounds added).

Then I got the Check Engine again .

Fault code reads 12, 46:

12 = Battery connection disturbed within the last 50 starts

46 = Charging system voltage too high

I've not disconnected the battery in a couple years. I have the internal regulator. You reckon my alternator is going or my ECU? And how do I determine which?

 

make sure your battery connections are tight and clean. I had the same thing happen, after about 3 times I started looking. Found a loose connection on the positive. Cleaned and tightened both cables and no problem after that.

 

Ah, good point. I'll eleminate that as an issue. Thanks,

 

On my old '93, I thought the alternator had gone bad as I had some of the same symptoms as you. Changed the alternator with no improvement. Took it to a mechanic with a diagnostic reader thing, and he told me it was the voltage regulator which is a part of the ECU. He didn't remove the ECU until I located a new one so that I could still use the truck. Finally found one 3 states away for $500. Brought it to the mechanic to swap it out and when he pulled the windshield washer tank off the fender to get at the ECU, he found a broken wire. Fixed the wire and the system charged fine after fixing the wire. Then I was stuck with a $500 ECU I didn't need. No returns on electrical parts.

Just make sure what the problem is before replacing parts!

chaikwa.

 

Why would you take the washer tank off the fender to get at the ecu which is behind the battery on the opposite side?

 

You could test the voltage regulator by getting an old style mopar one ($12 i think.), and temporarily wire it up. Unplug the battery to reset the codes and drive it a bit. If the codes come back its not the voltage regulator. Here is the instructions for hooking an external regulator up. https://www.dieseltruckresource.com/...n&onlynewfaq=1

 

Um... because it wasn't behind the battery on the opposite side maybe? Mine was behind something, (I don't remember what now, it was in 1999), and then just forward of the hood spring/hinge and partially behind the washer fluid tank, passenger side if I remember correctly.

Here's a pic;


chaikwa.

 

I'll give that a try.

From the sticky it looks like you just unhook the alt and leave the EOM harness hanging and then rewire it to the regulator & ignition hot. Easy.

Thanks,

 

Um, so I unhook the factory "plug" from the alt and I guess I bend/tape up the tabs that went to the alt and leave the other big wires alone right?

I comprehend how to wire up the regulator from the sticky, just making sure I'm dealing with the detritus from the OEM harness correctly...

 

If a neighbor or someone has a 1st Gen. with factory-equipped external regulator, you could look at the harness on it and it sort of explains itself.

The alternators are the same, with the exception that some of the earliest 1989 models had a Bosch, instead of a ND.


If you don't get it worked out, find yourself in my neighborhood and you can look at three on trucks and one loose on the bench.

 

Thanks BK, things always work better for me when I can see it instead of just reading about it.

But I was mainly was wondering about modifying the one's with an ECU.

As in trying to figure out if I keep the factory harness plugged up and wire in the external regulator in addition to or intead of. I'm assuming instead of so any stray instructions from the ECU don't confuse the new external regulator...

 

i get the same symtoms. i have an add in wanted for a new alt. when my check engine light comes on, i pop my hood, and tap on my alternator. it must have worn out windings inside. then it will start charging again.

 

Hey, somebody stole your air box .

Whats that thing hanging off your alt? Hydraulic pump?

 

OK, I'm back on my charging "problem"

Fault code reads 12, 46:

12 = Battery connection disturbed within the last 50 starts

46 = Charging system voltage too high

I removed the alt and it tested fine. I had already added several grounds from block to body (years before).

I'm assuming now that it is the internal regulator. I have the sticky on installing an external. I have the regulator and a plug.

I'm ready to wire in the external but what I need to know and what the sticky doesn't address is what do I do with the existing wires from the ECU to the alternator? Just leave them hanging? I'll just tape them up and zip tie them out of the way if they will be considered "dead".

Thanks

 

Yup, just tape them off, they don't need to be connected to anything.