SOLVED: I borrowed a scope and found that my issue was that the wires to the low beams are PDC (Pulsed DC) and that's why I was getting a reading of 10.4v on my volt meter with the engine running. Tested it with a test voltage regulator and no more voltage drop at the headlight low beam.

Hello,
Newbie here needing some electrical advice/help.

I have a 2009 E250 5.4L Extended body. My problem is that I have low voltage at the headlights, BUT only when the engine is running.
The van has a high output alternator with 4 batteries and it runs fine at 14.7v with all OEM accessories on. So I know it is not the alternator.

I invested in some LED lights to increase my night time driving visibility. Simple plug and play with a separate power wire for the DRL. Installed and all working great, except the low beams came on when I took it out of park. So I went in to the BCM (body control module) using Forscan to disable the OEM DRL. No more low beams when out of park except when I turn on the lights. So far all good.

Now just a note about the LED's... When you connect power to the DRL wire, the DRL come on as they should. Cut the power to the DRL and turn on the low beam and the DRL's also come on. I contacted the supplier with my concern and he mentioned that the OEM DRL shut off when the low beams are turn on, which I knew. What I didn't know is that these LED's I bought are intended for vehicles that have the DRL module at the front of the grill and you would use the DRL power source from that module to the red DRL wire of the LED lights. But in 2009 Ford discontinued the separate DRL module and incorporated it in the BCM (body control module). So I do not have a wire to run to my LED DRL wire and as he mentioned "you do not want to run two powers to the DRL, (1) from the red wire and (2) from the low beam when on".

So what is the alternate option I asked him... "it is to run an ignition source power wire to activate a primary relay using 12v power from the battery through the relay (so battery power is used to power the aftermarket DRL) to supply power to a secondary relay which in turn controls the ON/OFF of the aftermarket DRL by using a power source from the left headlight and connecting it to pin 86 and then a wire from pin 87A to the DRL wire. By doing this, it will activate the secondary relay to turn off the DRL lights when the low beams are turned on" he instructed.

So I did just that. All works great and proper voltage everywhere when the engine is not running. I start the engine, DRL turn on (all good) turn on low beams, the relay clicks off the DRL (all good) and then about two minutes the 2nd relay starts buzzing. It is buzzing because there is 10.4 volts supply to the relay from the head light low beam when the engine is running. Shut off engine and no buzzing and there is now 12.4 volts supply from the head light low beam. ???

So doing a bunch of tests (with the engine running), I found that the low beam power wire to the relay drops from 14.4v to 10.4 volts when connected to the relay. I did a test running power from the park lamps, from the battery and from the fog lights (not at the same time) to the relay, no buzzing and no drop in voltage. ???

A sub note: The van had the OEM chrome grill and plastic lights setup but was replaced by the previous owner with the black OEM grill and glass sealed beam setup after a hit and run before I bought it. Don't think this matters.

Any Ideas???


Thank in advance

 

Suggest you consider restoring what was disabled with forscan and see if you can get the system working properly again.

We can go from there once we have some idea of why it was done.

 

I did and it all it does is have the low beams come on as the DRL. That is why I disabled the OEM DRL.
BTW, not sure if you read my post before or after I edited it. I mention in detail the issue.

 

What does your owner's manual say in regard to when the DRLs are supposed to work and which beam it uses for DRLs?

 

It doesn't matter what it says. They are disabled via the BCM, just as if Ford would do if it was sold in the USA. The new headlights have their own DRL built in. No other 12v wire on the vehicle drops in voltage except the one headlight with the pigtail wire to the relay. Park lights and other circits tested stay the same voltage. Only the headlight drops in voltage. Spoke with dealer for 20 min this morning (all my company vehicles go there) and their top guy is as baffled as I am, and I used to work there lol. Kind of embarrassing lol.

 

As you know all vehicles are not the same.
Some fords ,have a separate relay for each headlamp and the only way I can tell is either with a schematic or the relay picture in the owner's manual.
If there is a separate relay,then you need to know which is for which side and verify if full power is getting out to the headlamp which if it is, then there could be a ground problem for that particular lamp very possibly at the plug for the bulb.

 

Hi Hanky and thanks for your replies
I know all that (I used to be a Ford Tech) and have the schematic in front of me via Ford Oasis which I still have access to. These models do not have external modules for the DRL and relays for the headlights. I did many of this type of setup on vehicles that came from the US and never had an issue.

Either way, I did find out the issue I'm having, which I was about to post. I swallowed my pride and went to the dealer to borrow their scope, well sure enough the headlight low beam is a PDC circuit which is not indicated in the schematics for this vehicle or in the Oasis help. That explains why I have 10.4v because the volt meter I was using doesn't detect puled DC voltage. So the meter thinks it is 10.4v. I went back to borrow what we called a "test filter", basically a voltage regulator. once I tapped it in, I got a reading of 14.3 (engine running YAY) and no pulsing on the scope.

So Basically I have to order a voltage regulator for my setup.

Again, thanks for your replies!

 

It sounds to me like the headlight control system is switching to DRL mode (although I don't know why) when you turn on the low beams with the engine on.
As you can see from the attached description, there is no separate DRL system. It's implemented in software to pulse width modulate (PWM) the low beam power to a lower voltage. This also explains why the factory DRLs go off when the low beams are on. There are no separate DRLs!
This PWM would likely result in the lower voltage you're seeing.
It likely also means the low beam headlights are not at full brightness.

I have also attached a wiring diagram for the headlights in case you may find that useful.

 

We were posting at the same time!

It still sounds to me like the SJB is pulsing the low beam circuit (trying to operate DRLs) when the low beams are on. Depending where you install the voltage regulator, you could get full power to the relay but still have the modulated (lower) voltage to the headlamps themselves which would reduce their brightness.

 

Hey thanks for the wiring diagram! Oasis? lol Yes I have the same. There's only a relay for the highs so I know that circuit is not pulsed, either way there wasn't any volt drop on the highs.

I know what my issue is at least. but like you said, I'll have to check and make sure I'm getting full power to the headlights. That was the whole reason in getting these LED. I couldn't see jack squat and a guy doing the same work as me has a few Chev Express vans and when in his the glass sealed beams give good visibility. I even bought and tried the same sealed beams he uses and still crap. But at least I know why now.

Thanks for replying !