Charging system problem and battery light
07-30-2014, 10:34 AM
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Charging system problem and battery light
I have a 2008 Ford F-150 with the 4.6L. The battery light came on so I tested the alternator and it was charging 11.5 V. Took the alternator off and had it rebuilt, still 11.5 V. Thinking the alternator was still bad, bought a new one and it's still charging 11.5 V. Load tested the battery and it was good and checked both connections and they were good. After that I checked all fuses in the passenger kick panel with a test light and actually pulling and looking at them, none were bad. I also checked the three fusible links under the hood, all were good. Next I checked the connector that clips on the alternator and put a new one on just to be sure for $5. I checked the voltage at the alternator terminal and it was getting the full 12 something volts. Next, I printed the wiring diagram and ohmed between the wire at the alternator and where it goes into the computer to make sure there were no breaks and all ohmed out fine. On the plug there is one wire that supposed to be hot at all times and it is. The wire that runs between the alternator and computer that is ""key on activated' is the wire doing nothing to excite the alternator. I'm leaning towards computer but don't want to just bolt parts on, especially that expensive! I don't know where to go next, any help would be appreciated. Also forgot to mention I put a scanner on it and received DTC "P0620 generator control circuit." Thanks!
Last edited by ryanfleming18; 07-30-2014 at 01:18 PM.
08-02-2014, 01:34 PM
#2
I have a similar problem, except it's charging at a normal voltage. The light is intermittent and random. The alternator is working fine, whether light is on or not. Happened after a tuneup. I replaced the alternator, no change in condition. I have just decided to live with it, unless somebody has a relatively easy fix, which I hope somebody does. Mine light started coming on immediately after the tuneup
11-13-2015, 01:12 AM
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T
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I have a 2008 Ford F-150 with the 4.6L. The battery light came on so I tested the alternator and it was charging 11.5 V. Took the alternator off and had it rebuilt, still 11.5 V. Thinking the alternator was still bad, bought a new one and it's still charging 11.5 V. Load tested the battery and it was good and checked both connections and they were good. After that I checked all fuses in the passenger kick panel with a test light and actually pulling and looking at them, none were bad. I also checked the three fusible links under the hood, all were good. Next I checked the connector that clips on the alternator and put a new one on just to be sure for $5. I checked the voltage at the alternator terminal and it was getting the full 12 something volts. Next, I printed the wiring diagram and ohmed between the wire at the alternator and where it goes into the computer to make sure there were no breaks and all ohmed out fine. On the plug there is one wire that supposed to be hot at all times and it is. The wire that runs between the alternator and computer that is ""key on activated' is the wire doing nothing to excite the alternator. I'm leaning towards computer but don't want to just bolt parts on, especially that expensive! I don't know where to go next, any help would be appreciated. Also forgot to mention I put a scanner on it and received DTC "P0620 generator control circuit." Thanks!
11-13-2015, 05:52 AM
#4
Mark
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I have a 2008 Ford F-150 with the 4.6L. The battery light came on so I tested the alternator and it was charging 11.5 V. Took the alternator off and had it rebuilt, still 11.5 V. Thinking the alternator was still bad, bought a new one and it's still charging 11.5 V. Load tested the battery and it was good and checked both connections and they were good. After that I checked all fuses in the passenger kick panel with a test light and actually pulling and looking at them, none were bad. I also checked the three fusible links under the hood, all were good. Next I checked the connector that clips on the alternator and put a new one on just to be sure for $5. I checked the voltage at the alternator terminal and it was getting the full 12 something volts. Next, I printed the wiring diagram and ohmed between the wire at the alternator and where it goes into the computer to make sure there were no breaks and all ohmed out fine. On the plug there is one wire that supposed to be hot at all times and it is. The wire that runs between the alternator and computer that is ""key on activated' is the wire doing nothing to excite the alternator. I'm leaning towards computer but don't want to just bolt parts on, especially that expensive! I don't know where to go next, any help would be appreciated. Also forgot to mention I put a scanner on it and received DTC "P0620 generator control circuit." Thanks!
11-25-2015, 09:15 PM
#5
just leave it alone!
My 2008 f-150 has the same problem. For the past year, the generator light go's on & off all the time,but alt. is working fine. Sometimes the gen light stay's on for hours & the gen. gauge on the instrument panel never moves at all.. It's just a computer reading problem. Had a computer reading on my truck while the light was on & it didn't show or register any errors or problems. keep your eye on the gen. needle.
11-27-2015, 05:51 PM
#6
Senior Member
I've had the same issue on my '05 5.4 for 5 months. The batt light comes on and the message center shows "check charging system". I have a new battery and new alternator from Rock Auto. It appears this is a nornal problem for these trucks and is in the instrument cluster. I decided to just live with it for now.
08-10-2019, 10:08 AM
#7
Charging system and battery light
Please keep in mind the wires are stranded wires, there are several smaller wires in the wire you are testing.Ohm's testing a wire - you need 1 strand to make a complete circuit but that one wire may not be enough to carry the amperage needed. disconnect both ends of the wire you wish to test and put 12v into the one end of the wire, use a headlight on the other end of the wire and ground the headlight, this will load test the wire. depending on what headlight, I use a normal halogen plug in low beam bulb which pulls 3 amps, the transistors in the module I think trip open at 6 amps. be sure to check and clean all your ground circuits and their connections. I found a charging / battery indicator light on caused by a very loose ground on the BCM at the passenger kick panel. If the module cannot ground the ground circuit will look for any place it can ground, dome lights will turn on for example. I used a program called FORscan and bought a $30 adapter connected computer to truck and found code P0562 - PCM Low Voltage. The code has not returned since I fixed my BCM and all the engine and body grounds.
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11-16-2022, 07:19 PM
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F150 charging issue
I have a similar problem, except it's charging at a normal voltage. The light is intermittent and random. The alternator is working fine, whether light is on or not. Happened after a tuneup. I replaced the alternator, no change in condition. I have just decided to live with it, unless somebody has a relatively easy fix, which I hope somebody does. Mine light started coming on immediately after the tuneup
