Mechanics

INTERNAL REGULATOR OR ECU PROBLEM

1993 Jeep Cherokee

Electrical problem
1993 Jeep Cherokee 6 cyl Four Wheel Drive Automatic 235000 miles

rebuilt alternator failed 4 times
is alternator internally regulated or ecu controlled
or broken wire where?
Avatar
Old john
August 24, 2008.



Output Wire Resistance (Voltage Drop) Test 1. Ensure battery is charged. Turn ignition off. Disconnect negative battery cable. Connect a 0-150 DC ammeter and a voltmeter (0-18 volts) to vehicle's charging system. See Fig. 1 . 2. Connect a carbon pile rheostat between battery terminals. Ensure carbon pile is in OFF position before connecting leads. 3. Connect one end of jumper wire to ground and other end to alternator field terminal Dark Green wire on rear side of alternator. See Fig. 2 . Connect negative battery cable. 4. Start engine. Reduce engine speed to idle. Adjust engine speed and carbon pile to maintain 20- amp current flow. Observe voltmeter reading. Voltage drop should be .5 volt or less. 5. If voltage drop is greater than .5 volt, inspect, clean and tighten all connections between alternator BAT (B+) terminal and positive battery post. If wire resistance (voltage drop) is okay, test is complete. Remove all test equipment.
CAUTION: Alternator has 2 field terminals. In step 3), DO NOT connect jumper wire to alternator field terminal Dark Green/Orange wire. Page 1 of 1 ALTERNATOR - NIPPONDENSO -1993 Jeep Cherokee


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Is your check engine light on? If yes turn the key from off to on three times, on the fourth one leave it in the on position, count the flasshes...22 would flash as 2 blinks, then a short puase, then 2 more blinks...if several codes are stored, the pause is longer between codes, code 55 will be the last code...do this and post all codes found...

Merlin2021
Aug 24, 2008.
I am having the same problem, but I don't have an amp meter to test it. When I jump started my jeep, it started right up. So I put a volt meter on the battery to see when the battery got to a full charge, but when I disconnected the jumper cables the batter voltage dropped from 13v to 7v within a minute and the engine died. So I took the alternator apart to inspect the brushes, and found them to be bad, so I ordered a new alternator. Could bad brushes cause a drop in voltage like that. I also did the code test and came up with 12, 41, and 55, 41 being the important one (an open or shorted condition in the generator field control circuit). So I assume it could be the alternator.

Tiny
JetMech198
Oct 11, 2008.
If the brushes are bad, yes replace the alternator. Charge the battery before you restart it with the new alt.

Merlin2021
Oct 11, 2008.
OK, So now I am really confused. I changed out the alternator, and guess what. Yep, it is still not charging. In my fault codes I am still getting the 41. So now I am thinking it is the ECM/PCM. Is the Voltage regulator in the ECM, or is it located somewhere else. Also, what is the connector that bolts directly to the alternator. Is this some kind of diode or something or is just a thick insalated connection? I am really at a loss, and I don't know where else to test or look. I have already ordered a new computer for it, but I would Like to do some more trouble shooting before it gets here. Any tips.

Tiny
JetMech198
Oct 16, 2008.
Take battery and alternator to autozone and have them tested they will put battery under load test to ensure battery does not have bad cell if has bad cell it will not take a charge they will let you know if alternator is putting out a charge and then let us know what the results are

Jnovack
Oct 16, 2008.
Well there is one problem with that. I am in the military and I am stationed in Japan and the closest thing to an Auto Zone is one of the Ma and Pop Shops off Base and none of them speak english. So this is something that I will have to figure out on my own and hopefully with your help too. I guess we will see what happens when I get my new ECM.

Tiny
JetMech198
Oct 16, 2008.
When I was in the Military(VietNam) we had a shop on base for service guy to use, and get help from more knowledgeable guys, Nothing like that on base? Remove the battery cover and see if all cells have water. Do not replace the ECN yet, codes 41 = charging system, alternator, but if the battery has a dead cell, this code will still set. Can also be fusible links, between the alt, and battery.

Merlin2021
Oct 16, 2008.
Ok, so I went and bought a new battery and it is still not charging, and I am still getting the 41 fault code, any ideas? I saw somewhere that there could be a short or an open wire causing the problem, so I started shooting wires again, and I did find something. I found a pink wire going to the radio that was shorting to ground. So I fixed that, but it is still not charging. I am defiantly at a loss. I should be getting my new ECM this week. I will post my results when I get it installed. Thanks for the help.

Tiny
JetMech198
Oct 19, 2008.
I have a chrysler car but I am having the same problem. I too swapped the alternator which didn't work. Any help is appreciated. Thanks

Tiny
Carnovice96
Oct 1, 2009.
This is for the 93 Jeep, I will aslo look up the car But I need the model?
TEST CH-2, ALTERNATOR FIELD NOT SWITCHING PROPERLY (CODE 41 ) 1. Put DRB-II in voltmeter mode. Check voltage of Automatic Shutdown (ASD) circuit by probing Dark Green/Orange wire (Dark Green/Black wire on Grand Cherokee and Grand Wagoneer) at back of alternator. If voltage is less than 10 volts, repair open circuit from ignition switch. If voltage is 10 volts or greater. go to next step. 2. Check voltage of alternator field driver circuit by probing Dark Green wire at back of alternator. If voltage is less than 10 volts, go to next step. If voltage is 10 volts or greater, go to step 6). 3. Turn ignition off. Disconnect and inspect PCM connector. Repair, if necessary. Disconnect alternator harness from back of alternator. Using an external ohmmeter, check field driver circuit (Dark Green wire) for resistance. If resistance is less than 5.0 ohms, replace PCM. If resistance is 5.0 ohms or greater, repair open in Dark Green wire. 4. Turn ignition off. Disconnect PCM connector. Disconnect alternator harness from back of alternator. Using an external ohmmeter, check for resistance between alternator field terminals. If resistance is 5.0 ohms or greater, replace alternator. If resistance is less than 5.0 ohms, go to next step. 5. With DRB-II in ohmmeter mode, check resistance in field circuit of alternator harness. If resistance is 5.0 ohms or greater, repair short to ground in field driver circuit (Dark Green wire). If resistance is less than 5.0 ohms, replace PCM. 6. Turn ignition off. Disconnect PCM connector. Disconnect alternator harness from back of alternator. Using an external ohmmeter, check for resistance in field driver circuit alternator harness terminal and cavity No. 20 on PCM connector. See Fig. 4 . If resistance is 5.0 ohms or greater, repair short to ground in field driver circuit (Dark Green wire). If resistance is less than 5.0 ohms, replace PCM. Perform CHARGING VERIFICATION (CH-VER) test. NOTE: Perform TEST CH-1, BATTERY CONDITION CHECK before proceeding.


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TEST CH-1, BATTERY CONDITION CHECK 1. If battery has a built-in hydrometer, go to step 2). Turn ignition and all accessories off. Ensure battery voltage is 12.0 volts or greater. If voltage is less than 12.0 volts, charge battery and go to step 3). 2. If battery hydrometer is Green, go to step 3).1f battery hydrometer is Yellow or a bright color, replace battery and perform CHARGING VERIFICATION (CH-VER) test. If battery hydrometer is dark in color, charge battery and go to next step. 3. Ensure battery cables, terminals and posts are clean and tight. Perform a battery load test by applying a 300-amp load for 15 seconds. Wait 15 seconds to allow battery to stabilize. Apply a load equal to 50 percent of battery cold cranking rating for 15 seconds and record minimum voltage reading. 4. See MINIMUM BATTERY VOLTAGE table. If battery is below volt age, replace battery and perform CHARGING VERIFICATION (CH-VER) test. If voltage reading is okay, go to next step. NOTE: Perform PRELIMINARY CHECKS under TROUBLE SHOOTING before proceeding. If battery shows signs of freezing or leakage, battery posts are loose or battery has low electrolyte level, DO NOT test.


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Merlin2021
Oct 3, 2009.