Go BottomElectrical Problem on 4300
 | mark105
Join Date: Jan 2004 Posts: 4 Wisconsin 
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2004-01-21 74682
Hoping someone has had this same problem to narrow my search. I have a 4300 with only about 75 hours on it. Lately have been noticing when working at night the headlights will dim for a few seconds, when this happens the tach will also drop the rpm's. Although the engine speed is not changing. This will occur every two to five minutes and just for about 3 seconds then back to normal lights and tach. Anybody have suggestions of where to start looking...thinking maybe a bad ground??
Thanks!
Mark
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2004-01-22 74698
I'd check with your dealer to see if it's normal--could be just the fairly normal workings of the regulator. You might try trickle charging the battery for 24 hours or so and see if that clears the problem. I don't know how the tack works but many gauge circuits are ballasted to a constant 9V so variations in alternator voltage don't affect gauge readings. If it's an electronic tack and it's ballasted there might be an issue. A manual would give procedures for troubleshooting the regulator. ....
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| popabear
Join Date: Jul 2003 Posts: 15 S. E. Michigan
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2004-01-23 74813
Mark this only happens at night? Try looking for a wire to ground problem in the lighting system wires. Have you added any new lights or other bolt ons? Could have a pinched wire. Also make sure the Alternator belt is tight This is for starters. ....
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2004-01-23 74827
Could be a ground problem.
Or a sudden sporadic load. There aren't too many heavy draw items on a diesel tractor. Glow plugs come to mind...... ....
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 | Chief
Join Date: Jul 2003 Posts: 4297 Southwest MiddleTennessee
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2004-01-23 74828
If in fact you are having a current draw event; you may have a problem with the engine intake grid heater system. The problem could be in the ignition switch, a relay, etc. You may have even pushed the key switch in by accident. (highly unlikely) The intake heater grids on my Cummins severely draw the current/voltage down. (i.e. around 7 volts on start up) This is normal. Does not sound normal on your 4300 though. Just a thought on a theory. ....
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| mark105
Join Date: Jan 2004 Posts: 4 Wisconsin
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2004-01-24 74948
It seems by the responses that the alternator or regulator could be the problem. This could be happening during the day, I probalby would'nt notice it as the the only reason I notice it at night is the lights dim so I look at the dash to see what is going on and the tach drops down to about 1/4 of current RPM. Just the tach, motor does not drop. I asked my dealer for ideas and the one thing he mentioned was the tach is run by impluses from the altenator not a sensor on motor. Faster the altenator spins more the tach reads. I have looked for loose wires and can not find anything...maybe a bad altenator. Would this be possible with such low hours?
Thanks!!! ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-01-24 74964
You might check the fan belt for tightness. Yes almost anything is possible even on a new hour machine but some things aren't too likely.
I should think about my ancient basic electronics. Off the top of my head, I think it's possible for an alternator problem to lower both lower the alternator voltage and frequency outputs, which could affect both the lights and tech readings. I believe regulators only affect voltage output and changing voltage output shouldn't affect that type of tach. ....
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| mark105
Join Date: Jan 2004 Posts: 4 Wisconsin
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2004-01-24 74976
Thanks for the feedback. The altenator belt seems pretty tight. Noticed today that it is acting up more then usual. Maybe it will eventually do it all the time so I can find the problem. Hate electrical problems...I think I would almost prefer for something to break. Then at least you know what to fix. I think my next step is to check the output on the altenator and see if it is consistent. One last thought, this is happening when blowing snow, wonder if snow could get on the belt and cause it to slip...kind of a long shot. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-01-25 75000
I symphasize. when I was teching in the AF we used to call it Brogan Maintenance. Beat on something and it either fixes it or breakes it so you can find what's wrong.
I'll now just babble and maybe something will pop up. I think the key to finding the problem is noting that the light dimming and tach drop go together and seem to be independent of low rpm. I originally thought a pulse couting tach might be fairly independent of voltage change but now I'm not so certain. I'll speculate on how it might work. Rectified AC fed either triggers a pulse generator or is fed to something like a zenor diode so only the peaks pass. Pulses go to a long RC circuit that is used to bias a semi-conductor. More rpm equals more pulses, which increases the bias and current flow. The tach is just an ampmeter.
If that's the way it works, then a intermiddant bad ground could affect both lights and tach, but so could a weak diode in the alternator bridge if output wan't sufficient to trigger a pulse. A format alternator test would be good. It might show something to run an independent ground from the tach to the battery negative pole. ....
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| mark105
Join Date: Jan 2004 Posts: 4 Wisconsin
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2004-01-25 75008
Tom, thanks for the info. I will try the ground from the altenator first then move onto testing the output. Thanks again! ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2004-01-26 75079
Morning: For my wacky theory I was thinking tach rather than alternator. There may be a separate ground wire for the tach. An independent ground for the alternator likely would be a lug on one of the mounting bolts--probably the same for the regulator. The idea here is to test for a general ground fault by providing an independent ground path to the battery. I've got to assume that you have some background in this stuff, but procedures in a manual should be followed to make most tests.
Poor ground for the alternator should show up as low output in a test. I never did them for my Ford, but I found the output terminal still was covered with Ford Blue paint from 20-years before. The problem was low charge rate and burnishing the terminal improved it. I did check for battery drain but it was normal. Excessive battery drain would confirm a weak diode or carbon dust. All my auxiliary circuits come off a feed that comes from the battery terminal on my starter solenoid through a fusible link. I also burnished all connections on the solenoid and feed from the battery.
My manual calls for a carbon load to carry out the tests. I don't have one but I'd could hookup a bunch of lights and accessories. The idea is that you can't tell if a regulator is working properly unless the system is loaded to nearly the alternator rating and the battery is in good condition and charged. ....
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