Low voltage to low beam headlight - how to resolve?

[tedderek]

I have a 2008 which I swapped the headlights out for LEDs bulbs. Both low and high beams have been working for over a year now. Over the last few months the passenger low beam started to become sporatic in operation. I used to be able to get it to turn back on by turning the headlights off and then back on. It is now at a point where the headlight does not turn on at all. Driver side and both high beams work fine.

 

I pulled out the DMM and checked the voltage going to the headlight and I am reading about 8.9V; far below the allowed 12V. The driver side is reading 13.5V - nicely charged battery. The low voltage was measured without the headlight in place. Driver side and both high beams have proper voltages.

 

I found that there is a left and right 10A fuse for the low beams. I swapped these and the problem still persists on the passenger side - thus eliminating any corrosion and fuse issue.

 

Any other suggestions? I have a CD for the electrical schematic but, it is from 2011, I cannot seem to get it loaded and all the other references I find on the internet are just money suckers in some form. My next step is to go through the wiring diagram and check where I am loosing voltage and need a decent diagram for tracing.

[tedderek]

I was thinking if there is a relay to actually turn the headlight on, then it may be a relay, yet I cannot find the location. If found, next step would be to swap the driver / passenger relay to see if the problem moves.

 

Worse case, I will just insert a relay and have the low voltage headlamp control a relay to power on the headlight directly from the battery. But this would be a pain as I will have to deal with specialty connectors, etc.

 

Some time ago I actually created a circuit board to power on the headlights of my '88 BroncoII. Still works!

Edited November 19, 2022 by tedderek

[pedro2u]

Not sure if this helps, but I found a diagram for 2008 online here:  https://portal-diagnostov.com/en/2020/04/11/headlights-ford-edge-sel-2008-system-wiring-diagrams/

 

And a used replacement headlight control module here in case that's the culprit:  https://www.ebay.com/itm/234122769083

 

Good luck!

[tedderek]

I found that link for the diagram as well. Problem is that they want money for a basic diagram that should be available. What I see is a big black blob for a diagram.

 

Not sure where the headlight control module is located on the Edge. Is this a typical issue? Just need to find where the voltage is dropping. I could start there.

[pedro2u]

I only mentioned the headlight control module because it's listed on the diagram.  I believe it's the sensor on your dash at the base and center of the windshield that turns your headlights on when it gets dark.  Probably not your issue.

 

If I'm reading it correctly from the diagram, it appears headlight power first goes from the battery (fused) over to the left headlight  via pin 3 BRN (VPWR) .  Power exits from the left headlight (VCC) on pin 5 BLU/GRY then goes to the right headlight pin 5.  I assume you've checked this path? If not, I might start there

 

Good luck

Edited November 19, 2022 by pedro2u

[tedderek]

I will see if I can find this in the shop manual I have.

[EddieHudson]

Try swapping out the bulbs and check the voltages.

Edited November 20, 2022 by 1004ron

[tedderek]

Eddie, I started the thread with those steps already included. I am using LED bulbs so current is not the main problem. Besides, when I measure the voltage, the headlamp is not installed, so something is dropping the voltage by 4 Volts in the system from the battery to the connector. This is why I am looking for a wiring diagram. The CD I have is not loading up the wiring diagram because of some .dll errors.

 

I am a 30+ year engineer - electronics, mechanical, optics, ergonomics, civil, marketing, etc. Just looking for a diagram to work and debug with. All sites out there are asking for money for a 14 year old vehicle - kind of crazy.

[tedderek]

Not finding much out there. Even for a headlamp module for the vehicle.

 

Worked up a small circuit that I will most likely add to the LED lamp replacement module. It will need the supplemental 12V from the battery, but will essentially use the low voltage seen going to the headlamp and switch in the 12V from the battery. This is an engineer's way of fixing things - create a solution that can be built and not cost a ton of money.

[tedderek]

I tested my circuit and it worked very well. The only problem is that I found that 8V was still going to the headlamp when the vehicle was turned off. This definitely points to the Smart Junction Box as being the problem.

 

I found some, but then it would have to be programmed at a cost of $200. So, back to the thinking.

 

OK, found a fairly simple solution. Worked out that most headlights take about 4A of current; for the incandescent / halogen types. The LED versions I am using draw just a bit over 1A. The end solution was the following.

• Obtain a set of headlight connector extenders. I found this on Amazon: www.amazon.com/dp/B00TXRWOPA
• For the good side, splice in a pair of wires, that will extend over to the failed side, into one of the extender cables.
• For the bad side, use the proper half to connect to the extended wires and use this to power the LED headlamp.
• The other half of this second extender is used to cap off the connector to ensure dirt and crud does not get in and cause problems.

After this, all is working well. Because one LED headlamps draws about 1/4 of the current of a regular headlamp, driving two off the same side will not put any stress on circuitry in the Smart Junction Box.