Checked wiring,fine. Slapped new 140A alt on and have not seen light since.
Battery Light! UGH!
Thread Starter
|
Senior User
Joined: May 2008
Posts: 374
Likes: 1
Battery Light! UGH!
My battery light is coming on in the mornings for up to about 14 miles. I am showing 13.2 to 13.6 volts with torque pro. The light hardly ever comes on in the afternoon, but sometimes. I had the batteries and alternator tested yesterday at Advance Auto parts. Alternator showed good both times they tested it. Batteries showed at or just above their rated cranking amps. I have inspected both negative grounds from the batteries, the engine ground from the firewall to the passenger side back side of the engine, and the body ground on the passenger side to the frame. They look great, tight, and have not moved in a long time. I added a cable from the alternator to the fender well and it showed about 7 amps while idling before dropping to about 4.5 amps.
I am thinking of still buying a new alternator anyway. That is the only think I can think of. Worse case, I just have a spare in the back of the truck. Any thoughts?
I am thinking of still buying a new alternator anyway. That is the only think I can think of. Worse case, I just have a spare in the back of the truck. Any thoughts?
Senior User
Joined: Jan 2015
Posts: 357
Likes: 0
I fought with a battery light for a few weeks. Did everything you did to check everything. Even took the alternator out and at it tested on the Bench at oreily and it passed. Ended up changing it and the battery light hast came back on in months. I got mine at orielys for 170.
Posting Guru
Joined: Nov 2012
Posts: 2,123
Likes: 5
As best I can tell there are 2 circuits in the voltage regulator if they show a certain amount of difference the light will be thrown but will still test good output.
I can only assume that a greater spread it would affect output and fail the test.
Who knows for shure.
I can only assume that a greater spread it would affect output and fail the test.
Who knows for shure.
Post Fiend
Joined: Aug 2007
Posts: 6,976
Likes: 0
From: At the Station
I too have this issue. Battery light came on Friday towing the camper, Scan Gauge showing 10-11 volts. Swapped new alternator voltages now showing 13-14 volts but the light is still coming on. Voltages have not dropped according to gauge
Trending Topics
Lead Driver
Joined: Feb 2011
Posts: 8,241
Likes: 155
From: L.A. (Lower Alabama)
Here are a couple of other considerations.
Checking Ripple Voltage
Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.
Alternator Leakage Current To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.
Checking Ripple Voltage
Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.
Alternator Leakage Current To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Hotshot
Joined: Jul 2005
Posts: 13,834
Likes: 26
From: Middle Tn.
Here are a couple of other considerations.
Checking Ripple Voltage
Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.
Alternator Leakage Current To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.
Checking Ripple Voltage
Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.
Alternator Leakage Current To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first.
Thread Starter
|
Senior User
Joined: May 2008
Posts: 374
Likes: 1
I replaced the alternator with a new 140 amp from Advance Auto. The brand is Tough One. My Torque pro was showing 14 after 2 minutes (which is about 14.4 at the battery).
I will know in the morning on the way to work if it fixed the battery light problem, but I feel good about it.
I will know in the morning on the way to work if it fixed the battery light problem, but I feel good about it.
Tuned
Joined: Mar 2007
Posts: 486
Likes: 6
From: Timmonsville
I replaced the alternator with a new 140 amp from Advance Auto. The brand is Tough One. My Torque pro was showing 14 after 2 minutes (which is about 14.4 at the battery).
I will know in the morning on the way to work if it fixed the battery light problem, but I feel good about it.
I will know in the morning on the way to work if it fixed the battery light problem, but I feel good about it.
Thread Starter
|
Senior User
Joined: May 2008
Posts: 374
Likes: 1
I always use Internet coupons at advance auto. That's why I buy everything there. But I always go to retailmenot.com to see what coupon codes are available first. Many times there are $40off of $100 or $50 off of $125. Since the Alternator was over $150, then $50 is the max savings anyway.
Thread Starter
|
Senior User
Joined: May 2008
Posts: 374
Likes: 1
2 days in a row with NO battery light. I think the alternator was the problem. Thank You All, for the help. We are off to Yellowstone in a week!! Hopefully I don't have to come home with a new truck!! Haha
Thread
Thread Starter
Forum
Replies
Last Post