Alternator change
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Junior User
Joined: Apr 2010
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Alternator change
I changed the alternator on my 2001 f150 5.4
Only problem was a squeal that was loud. I pulled it off then went to the parts store they only had the 130 amp so I got it and it works but my battery light is on.
-charging at 15.4 volts
-no fuses blown
Is the light on because the charge is too high?
Any suggestions would be great. Thanks.
Only problem was a squeal that was loud. I pulled it off then went to the parts store they only had the 130 amp so I got it and it works but my battery light is on.
-charging at 15.4 volts
-no fuses blown
Is the light on because the charge is too high?
Any suggestions would be great. Thanks.
Logistics Pro
Joined: Jul 2003
Posts: 3,595
Likes: 52
From: Lawton, Oklahoma
Make sure the regulator connector is seated fully, no spread pins, broken wires and power and ground are clean and tight. An open at the PCM monitored regulator circuit may cause the alternator to go full charge output.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
To help everyone understand how the complete charge circuit works here is a short 101.
On the alternator is a regulator.
In this regulator is a 'reference' circuit set at about 14 volts.
It is the difference between this reference and the actual battery voltage that causes the regulator to make the alternator force current into the battery until it comes up to the reference value in the regulator.
This is the charge control.
.
The dash lamp is a separate circuit.
Battery is fed to the lamp through the ignition switch.
The other side of the lamp goes to the regulator.
When the lamp is on the alternator is not outputting because the regulator is supplying a ground to light the lamp telling that the alternator is not outputting at a high enough level (that removes the ground) putting the light out.
.
Bottom line here is with the light on ''''and''' the voltage high suggest the regulator on the alternator is faulty since the alternator is outputting at 15+ but the light is still on because the regulator has not removed ground from the lamp due to a fault besides not controlling the charge rate.
Only other possibility is pins are shorted at the plug up point.
If not the case remove the alternator and return for a good unit having it tested before you leave the store.
Good luck.
On the alternator is a regulator.
In this regulator is a 'reference' circuit set at about 14 volts.
It is the difference between this reference and the actual battery voltage that causes the regulator to make the alternator force current into the battery until it comes up to the reference value in the regulator.
This is the charge control.
.
The dash lamp is a separate circuit.
Battery is fed to the lamp through the ignition switch.
The other side of the lamp goes to the regulator.
When the lamp is on the alternator is not outputting because the regulator is supplying a ground to light the lamp telling that the alternator is not outputting at a high enough level (that removes the ground) putting the light out.
.
Bottom line here is with the light on ''''and''' the voltage high suggest the regulator on the alternator is faulty since the alternator is outputting at 15+ but the light is still on because the regulator has not removed ground from the lamp due to a fault besides not controlling the charge rate.
Only other possibility is pins are shorted at the plug up point.
If not the case remove the alternator and return for a good unit having it tested before you leave the store.
Good luck.
Laughing Gas
Joined: Jan 2006
Posts: 1,098
Likes: 11
From: Minnesota
I went thru THREE alternators before I got a good one when mine went bad. Number 1 had a low growl in it like a bearing noise....they told me my serpentine belt was too tight... Number 2 sounded like I had a Whipple under the hood..they said my truck was drawing too many amps.... Number 3 sounded OK with just a medium hum when all the lights were on and the heater. That was 100,000 miles ago and it's still OK.
Even the auto parts guys admit they are junk. Buy the best one you can afford.
Even the auto parts guys admit they are junk. Buy the best one you can afford.
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I went back they said it tested fine so I told them to keep it. Went to another store and got the lower amp and worked great. Thanks for the help. That is what I thought I needed to do but it is better to get confirmation some times.
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