"check charging system"
#1
07-10-2015, 08:38 PM
"check charging system"
Hello all.
2004 Expedition XLT 5.4
My check charging system warning started going off for the past week, then the battery light and soon after the radio would die, voltage gauge would drop rapidly and the truck would die. Did a voltage test on the battery and found it was dropping about a volt after starting the engine. So I think, must be the alternator and head to the wrecker to see if he has one. He didn't, but says lets try something. Has me start the engine and he takes of the negative to the battery and the truck dies immediately. Says, "Yup, alternator all right". So I go down to the Ford dealership and buy the $500 part, get home and think, I'll test the voltage one last time, and now it goes 1.5 volts higher after starting, and after pulling the negative of the battery the truck keeps running?!?
I don't get it, any ideas.
2004 Expedition XLT 5.4
My check charging system warning started going off for the past week, then the battery light and soon after the radio would die, voltage gauge would drop rapidly and the truck would die. Did a voltage test on the battery and found it was dropping about a volt after starting the engine. So I think, must be the alternator and head to the wrecker to see if he has one. He didn't, but says lets try something. Has me start the engine and he takes of the negative to the battery and the truck dies immediately. Says, "Yup, alternator all right". So I go down to the Ford dealership and buy the $500 part, get home and think, I'll test the voltage one last time, and now it goes 1.5 volts higher after starting, and after pulling the negative of the battery the truck keeps running?!?
I don't get it, any ideas.
Last edited by Kelly G.; 07-10-2015 at 09:12 PM.
#2
07-10-2015, 09:13 PM
first of all, the jackass didn't know what he was doing. Your lucky he didn't damage your truck.
never, never run a vehicle with the battery removed from the system. the charging system can spike to full unregulated voltage and damage modules. the battery acts as a sump and the regulator needs to see battery voltage. full field output of alternator... yikes.
ten year old truck could have bad connections creating voltage drops across the insulated and grd circuits. a voltage drop on the battery posts from a bad connection would cause what you are reporting.
clean the posts at the battery, alternator and make sure the alternator is bolted in tight as it case grd thought the bolts. Then do voltage checks.
report actual measurements. 1.5v higher that an unknown battery voltage means nothing.
never, never run a vehicle with the battery removed from the system. the charging system can spike to full unregulated voltage and damage modules. the battery acts as a sump and the regulator needs to see battery voltage. full field output of alternator... yikes.
ten year old truck could have bad connections creating voltage drops across the insulated and grd circuits. a voltage drop on the battery posts from a bad connection would cause what you are reporting.
clean the posts at the battery, alternator and make sure the alternator is bolted in tight as it case grd thought the bolts. Then do voltage checks.
report actual measurements. 1.5v higher that an unknown battery voltage means nothing.
#3
07-10-2015, 11:26 PM
First, thanks for the advice Primem.
Ok I did what you said and it seems to be holding at the readings I got at my last test.
Which were:
First test after the truck died and I'd used a home charger - 12.5V (engine off), 11.9V engine running at idol with all on board electronics off. I had actually tried one other thing; I swapped with a 'known to be good' battery out of a f-150 and got the same readings.
Then after getting home from ford they were 12.47V off, 13.89V running. just now after cleaning the connections I got 12.45V and 14.23V.
Do you think there's any chance it may still be an alternator problem or would it be safe to bring the new one back? I'm thinking I should wait a day or two and take it for a little road trip just to see if the symptoms return.
Ok I did what you said and it seems to be holding at the readings I got at my last test.
Which were:
First test after the truck died and I'd used a home charger - 12.5V (engine off), 11.9V engine running at idol with all on board electronics off. I had actually tried one other thing; I swapped with a 'known to be good' battery out of a f-150 and got the same readings.
Then after getting home from ford they were 12.47V off, 13.89V running. just now after cleaning the connections I got 12.45V and 14.23V.
Do you think there's any chance it may still be an alternator problem or would it be safe to bring the new one back? I'm thinking I should wait a day or two and take it for a little road trip just to see if the symptoms return.
#4
07-11-2015, 08:47 AM
I think you are all ok at this point.
I suspect the system had voltage drops occurring on the grd and insulated(power) circuits.
reconnecting the bad connection may have fixed the problem. Monitoring the situation never hurts.
To check for voltage drops of the insulated and grd circuits. start the engine and turn on all electrical loads.
with a voltmeter put the red lead on the battery positive post and the black lead on the alternator output terminal. the reading should be less than 0.4volts.
then check the grd circuits. put the red voltmeter lead on the alternator case and the black leak on the negative battery post. the reading should be under 0.2 volts. If any of the reading are over the limit...there is resistance in the circuit dropping the available voltage sent back to the battery from the alternator.
I suspect the system had voltage drops occurring on the grd and insulated(power) circuits.
reconnecting the bad connection may have fixed the problem. Monitoring the situation never hurts.
To check for voltage drops of the insulated and grd circuits. start the engine and turn on all electrical loads.
with a voltmeter put the red lead on the battery positive post and the black lead on the alternator output terminal. the reading should be less than 0.4volts.
then check the grd circuits. put the red voltmeter lead on the alternator case and the black leak on the negative battery post. the reading should be under 0.2 volts. If any of the reading are over the limit...there is resistance in the circuit dropping the available voltage sent back to the battery from the alternator.
#5
07-11-2015, 11:59 AM
I agree 110% with the advice primem offered you !
That said , this is for any and all who may read this, Many years ago someone came up with the test of removing the battery cable to do a charging system check. I have never used it and would caution anyone thinking about trying it .
It's bad enough you can damage the alt itself, but when you send excessively high voltage through the electrical system , voltage sensitive components head for the frying pan and that can be a very expensive lesson, point is : DON'T DO IT !!
I have found that on the driver's side inner fender well is a junction where the heavy lead from the alt connects to another lead that supplies the output to the battery. Some of the junctions have a plastic cover over them and the connection still manages to get corroded. It's worth a check and if it needs to be cleaned remember it is a hot connection straight to the battery so be careful not to let any of the wires touch any other part of the vehicle.
That said , this is for any and all who may read this, Many years ago someone came up with the test of removing the battery cable to do a charging system check. I have never used it and would caution anyone thinking about trying it .
It's bad enough you can damage the alt itself, but when you send excessively high voltage through the electrical system , voltage sensitive components head for the frying pan and that can be a very expensive lesson, point is : DON'T DO IT !!
I have found that on the driver's side inner fender well is a junction where the heavy lead from the alt connects to another lead that supplies the output to the battery. Some of the junctions have a plastic cover over them and the connection still manages to get corroded. It's worth a check and if it needs to be cleaned remember it is a hot connection straight to the battery so be careful not to let any of the wires touch any other part of the vehicle.
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