aldive
Elite In Memoriam
- Joined
- January 17, 2001
- Messages
- 24,701
- Reaction score
- 27
- Year, Model & Trim Level
- 1999 XLT
In an endeavor to resolve my charging voltage at idle quandary ( http://www.explorerforum.com/forums/showthread.php?t=152430&highlight=alternator ),
I ordered an overdrive alternator pulley from Underdog Performance ( http://underdog-performance.com/index.html ). Of course it had to be red to match my underdrive water pump pulley (http://www.explorerforum.com/forums/showthread.php?t=153779&highlight=underdrive ).
The pulley cost $40.00 delivered to my door.
For those who don’t understand underdrive/overdriving, let me reiterate; to underdrive the crankshaft, you use a smaller ( than stock ) diameter pulley, whereas to overdrive the alternator ( or any other accessory ), you also use a smaller diameter ( than stock ) pulley; a larger pulley on an accessory would underdrive it.
My 130 amp alternator ( http://www.explorerforum.com/forums/showthread.php?t=139789&highlight=alternator ) is being underdriven via the UDP/harmonic balancer ( http://www.explorerforum.com/forums/showthread.php?t=151951&highlight=underdrive ); this overdrive pulley should restore the alternator speed to stock and restore my idle voltage issues.
To facilitate access ( since my air impact wrench would not fit with alternator attached to the motor ) to the alternator pulley retaining nut, the alternator had to be removed.
The first step in this mod was to disconnect the negative terminal of the battery. My Mac Intake ( http://www.explorerforum.com/forums/showthread.php?t=130982&highlight=mac+intake ) was then removed to gain access. The next step was to remove the serpentine belt by rotating the drive belt tensioner counterclockwise with a 3/8” breaker bar. Now the wire harness to the voltage regulator was unplugged and the B + terminal cover lifted and the nut (10 mm) and wire ( also the supplemental 4 gauge wire [ http://www.explorerforum.com/forums/showthread.php?t=152430&highlight=alternator ] removed. The 3 bolts ( 13 mm ) holding the alternator in place were detached as well as the additional grounding wire; then the alternator was detached from the truck. Air tools made removal a snap.
Subsequently, the alternator was padded and placed in my bench vice and the pulley nut (15/16”) removed with my air impact wrench.
The stock pulley was 2 9/16“ in diameter, whereas the overdrive pulley was 2“ in diameter. In contrast, an underdrive alternator pulley is 2 5/8“ in diameter.
The overdrive pulley was installed and the nut tightened with the air impact wrench and torqued to 80 ft/lbs. After that the alternator was reinstalled in the truck by reversing the removal procedure. A new ( size ) serpentine belt was not required for this mod, nor did I feel the need to replace the existing belt since it’s only a few weeks old. NOTE: after a couple weeks, the belt started squeeling; it was resolved via a 5060850 belt.
The motor was started and observed for any troubles; none were present.
After allowing the motor to reach operating temperature ( 190 F ), the voltage at idle was 13.4 volts ( as determined with my Dakota Digital [ http://dakotadigital.com ] voltmeter ). Idle voltage prior to the new pulley install was around 12 volts. The voltage at 1000 rpm was 14.0 volts. A short road test at 70 MPH, showed the voltage to be as before (13.9 volts) the mod. This test was in the daytime with high beam lights, the stereo/amp on and the AC blower on high.
This simple and inexpensive mod took about 30 minutes at a unhurried pace.
Finally, the voltage at idle problem appears to have been resolved. This sure beats purchasing an expensive new alternator ( even though a glistening red one would be nice ) that might have the same idle voltage issue.
I ordered an overdrive alternator pulley from Underdog Performance ( http://underdog-performance.com/index.html ). Of course it had to be red to match my underdrive water pump pulley (http://www.explorerforum.com/forums/showthread.php?t=153779&highlight=underdrive ).
The pulley cost $40.00 delivered to my door.
For those who don’t understand underdrive/overdriving, let me reiterate; to underdrive the crankshaft, you use a smaller ( than stock ) diameter pulley, whereas to overdrive the alternator ( or any other accessory ), you also use a smaller diameter ( than stock ) pulley; a larger pulley on an accessory would underdrive it.
My 130 amp alternator ( http://www.explorerforum.com/forums/showthread.php?t=139789&highlight=alternator ) is being underdriven via the UDP/harmonic balancer ( http://www.explorerforum.com/forums/showthread.php?t=151951&highlight=underdrive ); this overdrive pulley should restore the alternator speed to stock and restore my idle voltage issues.
To facilitate access ( since my air impact wrench would not fit with alternator attached to the motor ) to the alternator pulley retaining nut, the alternator had to be removed.
The first step in this mod was to disconnect the negative terminal of the battery. My Mac Intake ( http://www.explorerforum.com/forums/showthread.php?t=130982&highlight=mac+intake ) was then removed to gain access. The next step was to remove the serpentine belt by rotating the drive belt tensioner counterclockwise with a 3/8” breaker bar. Now the wire harness to the voltage regulator was unplugged and the B + terminal cover lifted and the nut (10 mm) and wire ( also the supplemental 4 gauge wire [ http://www.explorerforum.com/forums/showthread.php?t=152430&highlight=alternator ] removed. The 3 bolts ( 13 mm ) holding the alternator in place were detached as well as the additional grounding wire; then the alternator was detached from the truck. Air tools made removal a snap.
Subsequently, the alternator was padded and placed in my bench vice and the pulley nut (15/16”) removed with my air impact wrench.
The stock pulley was 2 9/16“ in diameter, whereas the overdrive pulley was 2“ in diameter. In contrast, an underdrive alternator pulley is 2 5/8“ in diameter.
The overdrive pulley was installed and the nut tightened with the air impact wrench and torqued to 80 ft/lbs. After that the alternator was reinstalled in the truck by reversing the removal procedure. A new ( size ) serpentine belt was not required for this mod, nor did I feel the need to replace the existing belt since it’s only a few weeks old. NOTE: after a couple weeks, the belt started squeeling; it was resolved via a 5060850 belt.
The motor was started and observed for any troubles; none were present.
After allowing the motor to reach operating temperature ( 190 F ), the voltage at idle was 13.4 volts ( as determined with my Dakota Digital [ http://dakotadigital.com ] voltmeter ). Idle voltage prior to the new pulley install was around 12 volts. The voltage at 1000 rpm was 14.0 volts. A short road test at 70 MPH, showed the voltage to be as before (13.9 volts) the mod. This test was in the daytime with high beam lights, the stereo/amp on and the AC blower on high.
This simple and inexpensive mod took about 30 minutes at a unhurried pace.
Finally, the voltage at idle problem appears to have been resolved. This sure beats purchasing an expensive new alternator ( even though a glistening red one would be nice ) that might have the same idle voltage issue.
