headlights surge
Thread Starter
|
4th Gear
Joined: Dec 2011
Posts: 4
Likes: 1
From: Burnt Ranch, Ca
headlights surge
2003 F-250 6.0 187,000 miles
I have recently noticed going down the road that the headlights will surge. They will go bright then dim. They don't go real bright or super dim. I have replaced the batteries recently and noticed it prior to replacing the batteries.
Anyone experience this?
Adam
I have recently noticed going down the road that the headlights will surge. They will go bright then dim. They don't go real bright or super dim. I have replaced the batteries recently and noticed it prior to replacing the batteries.
Anyone experience this?
Adam
Hotshot
Joined: Dec 2014
Posts: 17,823
Likes: 3,101
From: Jersey Shore
There are two things that can contribute to this. Varying amount of alternator output or varying amount of load.
Hopefully you are driving around with some type of monitoring system other than relying on the stock gauges. With that you can monitor the voltage output.
If it is the alternator, you might see an occasional battery light or a dim battery light. The “battery light” really doesn’t tell you about the batteries, it tells you the alternator is not charging.
Output variation can also occur if the drive belt is slipping.
For a varying load that pulls current and lowers the voltage to dim the lights, the glow plug control module can be failing.
Hopefully you are driving around with some type of monitoring system other than relying on the stock gauges. With that you can monitor the voltage output.
If it is the alternator, you might see an occasional battery light or a dim battery light. The “battery light” really doesn’t tell you about the batteries, it tells you the alternator is not charging.
Output variation can also occur if the drive belt is slipping.
For a varying load that pulls current and lowers the voltage to dim the lights, the glow plug control module can be failing.
Cargo Master
Joined: Aug 2003
Posts: 2,332
Likes: 442
From: Eastern Washington
Yeah, get a voltage reading while the headlights are dimming. Either the obdii port or cig lighter would be good enough for reference.
14+ volts is what your looking for, the first couple of minites will be lower due to glow plugs cycling.
A failing alternator, cracked wiring at the plug, loose battery connections, corroded cables can all cause similar issues.
A worn belt slipping when the AC compressor cycles could do it as well.
14+ volts is what your looking for, the first couple of minites will be lower due to glow plugs cycling.
A failing alternator, cracked wiring at the plug, loose battery connections, corroded cables can all cause similar issues.
A worn belt slipping when the AC compressor cycles could do it as well.
Cargo Master
Joined: Nov 2015
Posts: 3,419
Likes: 932
From: Fort Worth, TX
Yeah, get a voltage reading while the headlights are dimming. Either the obdii port or cig lighter would be good enough for reference.
14+ volts is what your looking for, the first couple of minites will be lower due to glow plugs cycling.
A failing alternator, cracked wiring at the plug, loose battery connections, corroded cables can all cause similar issues.
A worn belt slipping when the AC compressor cycles could do it as well.
14+ volts is what your looking for, the first couple of minites will be lower due to glow plugs cycling.
A failing alternator, cracked wiring at the plug, loose battery connections, corroded cables can all cause similar issues.
A worn belt slipping when the AC compressor cycles could do it as well.
Thread Starter
|
4th Gear
Joined: Dec 2011
Posts: 4
Likes: 1
From: Burnt Ranch, Ca
Thank you for the replies! I have been off grid for a bit.
I do not have a monitoring system installed YET! I put a voltmeter on the battery the voltage fluctuates between 13 and 15. How do I test the glow plug control module? I will attempt to see if the surge is happening with the A/C cycling, putting a draw on the belt & making it slip.
I do not have a monitoring system installed YET! I put a voltmeter on the battery the voltage fluctuates between 13 and 15. How do I test the glow plug control module? I will attempt to see if the surge is happening with the A/C cycling, putting a draw on the belt & making it slip.
Cargo Master
Joined: Aug 2003
Posts: 2,332
Likes: 442
From: Eastern Washington
After it's warmed up you can unplug the glow plug control module to eliminate it as a cause. Or disconnect the power for it from the pass battery. To eliminate the AC just turn off the hvac and see if it still has an issue.
Cargo Master
Joined: Nov 2015
Posts: 3,419
Likes: 932
From: Fort Worth, TX
You need to use a voltmeter that measures decimals. If not that 13 volts could really be 12.6.
Also, 15 volts is way too high. If that reading is accurate, you need an alternator.
Also, 15 volts is way too high. If that reading is accurate, you need an alternator.
Trending Topics
Hotshot
Joined: Dec 2014
Posts: 17,823
Likes: 3,101
From: Jersey Shore
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Fleet Mechanic
Joined: Sep 2006
Posts: 1,491
Likes: 295
From: Fresno, CA
Thread
Thread Starter
Forum
Replies
Last Post