2001, Pulsating Lights
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2001, Pulsating Lights
2001 F150 4x4 5.4 gasoline, 200k miles
I have had the vehicle for about 3 years now. One thing I noticed when originally I got it, was that all the lights, headlights, tail lights, dome light, instrument panel lights would pulsate at a steady rate when it was running. It did not matter whether it was idling or doing 70 on the highway.
When I bought the truck, the stock plastic headlights had long since seen better days. So shortly after I bought it, I swapped out the headlights with new high intensity ones. Each side has it's own high voltage power supply. They have worked fine since I installed them.
Tonight I left the truck running when I parked, and I got out and looked at all the lights. Headlights are fine and steady.
All the other lights, parking, instrument, tail, dome, are still pulsing. It is a steady constant pulsation of less than 1/2 second pulse. The only light that was not visibly pulsing was the digital display on the radio.
What could be the culprit here? Ignition noise?
I have never replaced the alternator. It may be original.
The battery is less than a year old.
Again, it's done this pulsing since day 1, when I bought it used and BEFORE I replaced the stock headlights.
I have had the vehicle for about 3 years now. One thing I noticed when originally I got it, was that all the lights, headlights, tail lights, dome light, instrument panel lights would pulsate at a steady rate when it was running. It did not matter whether it was idling or doing 70 on the highway.
When I bought the truck, the stock plastic headlights had long since seen better days. So shortly after I bought it, I swapped out the headlights with new high intensity ones. Each side has it's own high voltage power supply. They have worked fine since I installed them.
Tonight I left the truck running when I parked, and I got out and looked at all the lights. Headlights are fine and steady.
All the other lights, parking, instrument, tail, dome, are still pulsing. It is a steady constant pulsation of less than 1/2 second pulse. The only light that was not visibly pulsing was the digital display on the radio.
What could be the culprit here? Ignition noise?
I have never replaced the alternator. It may be original.
The battery is less than a year old.
Again, it's done this pulsing since day 1, when I bought it used and BEFORE I replaced the stock headlights.
Last edited by Eric_in_oklahoma; Jun 15, 2013 at 09:54 PM. Reason: correction
Hotshot
Joined: Jan 2004
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From: St Louis
What you're seeing is the alternator output "searching" for the correct regulated output. As it oscillates, its output rises and falls and causes the lights to give the pulsating effect. Everything still works, but is can be annoying to the driver.
It might be a bad voltage regulator or alternator or it might be a slight defect (excessive resistance) in the wiring in the battery voltage sense circuit.
Conturds were bad for this and my 98 exhibits the symptom in the winter. Ford finally put out a TSB for the issue in which they recommended looping back the sensing circuit right at the alternator instead of getting it the power box in the opposite side of the engine compartment.
I haven't heard much of this issue with the F-series, so it's likely uncommon. Therefore, I'd suspect the alternator itself is likely your issue.
It might be a bad voltage regulator or alternator or it might be a slight defect (excessive resistance) in the wiring in the battery voltage sense circuit.
Conturds were bad for this and my 98 exhibits the symptom in the winter. Ford finally put out a TSB for the issue in which they recommended looping back the sensing circuit right at the alternator instead of getting it the power box in the opposite side of the engine compartment.
I haven't heard much of this issue with the F-series, so it's likely uncommon. Therefore, I'd suspect the alternator itself is likely your issue.
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2001 5.4 F150 Pulsating Lights
I would agree the alternator/voltage regulator seems a likely issue.
I just took a look at the alternator, it has a remanufactured sticker on it.
Next questions.
Is the voltage regulator replaceable by itself? From what I see online, it seems it is. Though I know that the bearing could go out on the alternator a week later. But the voltage regulator would only cost me about $18. Worth a shot?
If not, do I go with a Ford dealer alternator or another remanufactured alternator?
What all is done on remanufactured units anyway?
Do they replace the bearings?
Just spray it down with some cleaner, box it up and resell it? Always seems very sketchy exactly what was and was not done.
Are any of these remanufactured units done in the US/Canada or is it all Chinese stuff?
I just took a look at the alternator, it has a remanufactured sticker on it.
Next questions.
Is the voltage regulator replaceable by itself? From what I see online, it seems it is. Though I know that the bearing could go out on the alternator a week later. But the voltage regulator would only cost me about $18. Worth a shot?
If not, do I go with a Ford dealer alternator or another remanufactured alternator?
What all is done on remanufactured units anyway?
Do they replace the bearings?
Just spray it down with some cleaner, box it up and resell it? Always seems very sketchy exactly what was and was not done.
Are any of these remanufactured units done in the US/Canada or is it all Chinese stuff?
Last edited by Eric_in_oklahoma; Jun 16, 2013 at 01:14 PM. Reason: additions
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Voltage Regulator, No Joy
Swapped out the voltage regulator today in hopes of curing the pulsating light syndrome, which is annoying.
Before I did anything, checked the battery voltage with the truck off and then running. All good. Charging right up around 15v.
Took the alternator off, swapped out the voltage regulator with a new unit. Buttoned it all back up. Reconnected the battery. Started. Lights still doing the exact same thing.
Well it was worth a shot. It's not affecting the way the truck runs. It's just annoying to have the lights pulsing all the time at night.
Before I did anything, checked the battery voltage with the truck off and then running. All good. Charging right up around 15v.
Took the alternator off, swapped out the voltage regulator with a new unit. Buttoned it all back up. Reconnected the battery. Started. Lights still doing the exact same thing.
Well it was worth a shot. It's not affecting the way the truck runs. It's just annoying to have the lights pulsing all the time at night.
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Joined: Sep 2006
Posts: 7,907
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The only thing that will make the lights pulse is a change in voltage.
From any cause from a faulty regulator, alternator, sense circuit, an alternating heavy load on the system etc.
You have to begin sectionalizing the circuits to see where the issue is originating from.
Certainly a voltmeter will show the change in voltage if the you see it in the lighting.
The HID system is a conversion stepping up to high voltage where the percentage of change is much less the bulbs are fed with so you may not notice it but it's there.
Almost no one has one but a Scope put on the system would show the pulsing display and what shape the wave form is. Then go looking for the cause.
For example if the wave form were a near square wave type, it is a load switching on and off.
If a smooth sine type it is a regulated varying source.
It can be found but you have to do extended diagnostics.
Start at the alternator. Inhibit it's operation and see what result you get.
Good luck.
From any cause from a faulty regulator, alternator, sense circuit, an alternating heavy load on the system etc.
You have to begin sectionalizing the circuits to see where the issue is originating from.
Certainly a voltmeter will show the change in voltage if the you see it in the lighting.
The HID system is a conversion stepping up to high voltage where the percentage of change is much less the bulbs are fed with so you may not notice it but it's there.
Almost no one has one but a Scope put on the system would show the pulsing display and what shape the wave form is. Then go looking for the cause.
For example if the wave form were a near square wave type, it is a load switching on and off.
If a smooth sine type it is a regulated varying source.
It can be found but you have to do extended diagnostics.
Start at the alternator. Inhibit it's operation and see what result you get.
Good luck.
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