Voltage dropping?
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Tuned
Joined: May 2014
Posts: 316
Likes: 16
From: Richmond, VA
Voltage dropping?
05 F-150 Lariat, 5.4 4x4
Occasionally at highway speeds (55 - 75 mph/1,400-2,000RPM) my headlights and dash lights will dim momentarily. It happens rarely, maybe once every 75-150 miles. I'm concerned because I'm 500 miles from home. I checked my battery voltage with all of the accessories running (high beams on, blower at full, radio on, wipers on...you get the idea) and was still reading 14.6 volts. I don't have an actual voltmeter in the truck when I'm driving (thanks Ford) so I don't know how much it's dropping, but it's not enough to set off any dash lights. I'm considering that it might be the EATC system making adjustments and causing the voltage to dip. Any thoughts? I don't want to pull the alternator if I don't have to, it's in a PITA spot.
Occasionally at highway speeds (55 - 75 mph/1,400-2,000RPM) my headlights and dash lights will dim momentarily. It happens rarely, maybe once every 75-150 miles. I'm concerned because I'm 500 miles from home. I checked my battery voltage with all of the accessories running (high beams on, blower at full, radio on, wipers on...you get the idea) and was still reading 14.6 volts. I don't have an actual voltmeter in the truck when I'm driving (thanks Ford) so I don't know how much it's dropping, but it's not enough to set off any dash lights. I'm considering that it might be the EATC system making adjustments and causing the voltage to dip. Any thoughts? I don't want to pull the alternator if I don't have to, it's in a PITA spot.
Fleet Mechanic
Joined: Apr 2016
Posts: 1,653
Likes: 193
Me I wiould clean my battery connectors and all connections to grd .
Tighten starter lead positive ,clean all engine compartment grds and the ones inside left and right kick panel . Not to mention leads on alternator use contact cleaner on plug . It could be a corroded connection or loose connection . Air conditioner clutch can cause this some, depending on how bad it is but only momentarily . .
You can drill a hole to get two leads thru floor board or fire wall, . It would be a good idea to use an inline fuse at the positive end at battery clip leads to battery get meter in area you can see it in cab .Put alligator clip leads on end to connect to battery . Do a good job so you trust your leads .
I doubt that a wire is shorting because you are not blowing fuses . But you have moving parts inside alternator ,slip rings etc . Could also be ambient heat is causing a bad connection after awhile . alternators do go bad--- use only OEM reman .
You can drill a hole to get two leads thru floor board or fire wall, . It would be a good idea to use an inline fuse at the positive end at battery clip leads to battery get meter in area you can see it in cab .Put alligator clip leads on end to connect to battery . Do a good job so you trust your leads .
I doubt that a wire is shorting because you are not blowing fuses . But you have moving parts inside alternator ,slip rings etc . Could also be ambient heat is causing a bad connection after awhile . alternators do go bad--- use only OEM reman .
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