External regulator conversion question

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jos51700

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The CEL in my '93 Dakota just tossed the dreaded OBDI Code 41: Alternator field control circuit open or shorted.
Now, those of us with any Mopar truck or Jeep newer than the late '80's (OR any Magnum-powered factory-EFI conversions, hence the relevance here) have probably faced this by now; the voltage regulator is driven by the "logic module" (fancyspeak interpretation: "Computer") and said logic module no longer sees the logic in continuing to regulate voltage. This is, often, the sole instigator of the code and indicative of a pending dead charging system.

In my case, I'll be installing a new battery just because the green-top Interstate is eight years old (what ever happened to the five year warranty, anyway? F'en EPA...) and is beginning to smell like it's leaking.

If the issue persists, one must weigh one's options....

Option 1: replace computer.
response: No. Ka-ching....and if you have one of the long disco'd OBD1 performance computers, this is a downgrade as well as an insult.

Option 2: external regulator! This is easy, instructions are everywhere so I'll not rehash them, I'll let Ramcharger Central user Slanted_Mind summarize them:
VRwiring.jpg


I'm going to wait to hook it up, but I'll go ahead and install the external regulator including a handy connector so that even if the on-board regulator commits Harikari, I'll have a side-of-the-road option ready to plug in.
response: B-b-b-b-but my CEL is still on!

So, these people (ERCKFRM Combo - Heavy Duty Chrysler, Dodge, Jeep External Voltage Regulator Kit with Field Replacement Module) make a "module" to make the CEL go back out (most of the time).
erckfrmupdate.jpg
See it? It's there on the lower left.
Module, my foot. It's a bigass high wattage resistor.
Better pic?
erckfrm.jpg


(Please note: I won't be buying their kit for this, but I will use their page to order alternator parts for rebuilding what's on hand here at Rancho del Cheapo, in the event of EMP attack.)

Does anybody here know what the resistance on that thing is? Another site said their 'electrical engineer dad' came up with four 10W resistors in parallel. I work with some EE's so I might ask them, but I doubt that will generate (ha-ha!) much of an answer.

As I understand it, this will get soldered into the now-disconnected wires for the Logic Module (there's that fag talk we talked about) and fool the Logic Module (my ex wife is 'tarded. Now she's a pilot) into seeing a circuit, even if that circuit isn't doing anything. Think I could pirate said circuit off some lost soul at U-Screw-It and make my CEL go out that way? I'm a big fan of using my CEL to observe things (my truck has a volt gauge, so that's ok), and if I stare at a lit CEL all day, it's going to get burned out via garbage bin.

Suggestions? What the hell is the resistance on the magic resistor? Where does it go? Anybody know?
 
Sounds like the resistor serves as a make shift, field load. The field is electromagnet, with significant inductance. The resistor will not serve as an acceptable replacement, in a manner to eliminate CEL. It will just consume power, and get hot. I can comment more... If the field controller is FUBAR, then adding the resistor is senseless.

It should not be hard to follow field control circuit, via wires and identify the power transistor (IGBT) that is defective and replace it. It will likey be in a TO-220, DPak, or D2Pak. If the alternator was over charging, the transistor is likely shorted. That can be easily identified with multi-meter. Shorts also can lead to burned traces (open), so other repair may be necessary.

Yes external regulator works if properly wired.
 
Sounds like the resistor serves as a make shift, field load. The field is electromagnet, with significant inductance. The resistor will not serve as an acceptable replacement, in a manner to eliminate CEL. It will just consume power, and get hot. I can comment more... If the field controller is FUBAR, then adding the resistor is senseless.

It should not be hard to follow field control circuit, via wires and identify the power transistor (IGBT) that is defective and replace it. It will likey be in a TO-220, DPak, or D2Pak. If the alternator was over charging, the transistor is likely shorted. That can be easily identified with multi-meter. Shorts also can lead to burned traces (open), so other repair may be necessary.

Yes external regulator works if properly wired.

Dude, teach me!
 
I might be able to help with your pictures id you want to try transistor replacement. Transistors have 3 to 4 leads, go in one way. Likely surface mount. Typically cut two small leads close to part, then unsolder tails. The tab on the body under part, sinks heat, older parts have middle lead that is same as tab, on PCB thru hole. Surface mount uses tab and two leads. Some boards are not boards, but flex circuits using kapton (amber looking tape) and copper traces, bonded to aluminum case. I am not familiar with what a 93 has. I make my own ECUs, and able to fix most stuff. I help, but do not fix for others.
 
Common problem and I have read on Dodge truck forums where others have tapped the factory wires to install an external 1970's Vreg. Search for those. They might also tell how to make the CEL turn off. My 1996 Voyager is similar, w/ the Vreg integral w/ the Power Control Module (PCM). I recall it uses the same circuit as a 1970's Mopar, one field +IGN and the downstream field going to a transistor (low-side control). The circuit is fairly independent of the rest of the PCM, it was just cheaper to package it there, plus whatever wiring might be for the check function.
 
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