2001 alternator trouble
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5th Wheeling
Joined: Apr 2003
Posts: 47
Likes: 0
From: Florida
2001 alternator trouble
I have a 2001 f150 4.6 4x4 with about 120k miles. around a year ago my alternator light came on I pull the alternator off and found the brushes were bad I put in a new set and all was good! Until today light came on again having been down this road befor I took it off and opend it up sure enough the brushes are bad again this time the slip ring the brushes ride on was badly worn. So I picked up a new brush holder and new roter instaled the new parts and put it back in the truck. It worked for about 10 min then the light came on again and soon the gauge started to drop.
The light stays on at idle but at 800rpm and above it goes out. I dont think it is charging even though the light is out. It was dark and raining when I left the house so with the head lights and wipers the battery goes fast I had to pull over several times and rev the engine to 3000rpm to get a little charge out of the alternator so I could make it back home.
Does anyone have an idea Thanks
The light stays on at idle but at 800rpm and above it goes out. I dont think it is charging even though the light is out. It was dark and raining when I left the house so with the head lights and wipers the battery goes fast I had to pull over several times and rev the engine to 3000rpm to get a little charge out of the alternator so I could make it back home.
Does anyone have an idea Thanks
Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
Really don't know about the newer stuff, but alternators used to have 2 sets of triple diodes.
If one or more diodes failed in either set it caused problems. Sometimes a severe reduction in the output current.
If it has diodes, you can check them with a meter. (low resistance in one direction, open the opposite way -- the meter should have a little diode symbol on the range that will work)
If one or more diodes failed in either set it caused problems. Sometimes a severe reduction in the output current.
If it has diodes, you can check them with a meter. (low resistance in one direction, open the opposite way -- the meter should have a little diode symbol on the range that will work)
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Seems you are just fixing the end result and not finding the cause.
Fast brush wear is from excessive arcing.
Since you just relaced the brushes the first time, the same condition ate away the brushed and 'continued' to eat away the rings.
Test the system to determine the whole operation so you can pick up the fault.
A charging system is very dynamic and needs to be looked at from what the regulator does after starting and after the battery has recovered it's charge.
A bad battery, a faulty regulator, faulty alternator diode stack all cause issues.
They all must be perfect in operation or you will continue to have a problem.
Charge 101:
Starting from a fully charged battery;
1 starting draws the battery down.
2. the regulator compairs battery voltage to it's internal reference and adjusts the charge current rate from the alternator.
3. as battery voltage rises, the charge current/voltage tapers down.
Anything that prevents these functions will be a big problem.
Good luck.
Fast brush wear is from excessive arcing.
Since you just relaced the brushes the first time, the same condition ate away the brushed and 'continued' to eat away the rings.
Test the system to determine the whole operation so you can pick up the fault.
A charging system is very dynamic and needs to be looked at from what the regulator does after starting and after the battery has recovered it's charge.
A bad battery, a faulty regulator, faulty alternator diode stack all cause issues.
They all must be perfect in operation or you will continue to have a problem.
Charge 101:
Starting from a fully charged battery;
1 starting draws the battery down.
2. the regulator compairs battery voltage to it's internal reference and adjusts the charge current rate from the alternator.
3. as battery voltage rises, the charge current/voltage tapers down.
Anything that prevents these functions will be a big problem.
Good luck.
