Thanks to DonSmith for contributing this article. This tech article was originally posted at FordF150.net. It is primarily intended for 1990"s-2000"s Ford trucks but most likely also applies to other Ford models and years.
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Why was this article created?There seems to be a lot of confusion about Daytime Running Lights (DRL) on the Ford F150trucks.How to enable them, how to disable them.Can I use the existing wiring harness to do thisor do I need the Ford "kit" to do it?Where do I get the parts to enable them?Whatare the part numbers?The following article was created to help you with enabling or disabling DRL foryour truck.
How DRL Works:1999 and newer:From the manual:The DRL are implemented by using the low beams at a reduced voltageof approximately 80% system voltage. This is accomplished by inserting a DRL resistor in series with thelow beam filaments. When the headlamp switch is engaged, the daytime running lamp function is disabledand the low beam filaments receive 100% system voltage.What it means: The DRL Relay Block enablespower to the low beams and the resistor changes thevoltage going to the low beams from 12 volts to 10 voltsthus making them dimmer.In trucks that donot have DRL a loop-backplug is in place of the Relay Block which providesground to the Multifunction Switch (Steering ColumnHigh/Low/Flash to Pass switch) so the normal low andhigh beam lights still work.
1998 and older: (Sorrypeople... very limited information on this one)From the manual:The DRL systemis designed to turn the high beam headlamps on at areduced output without illuminating the high beamindicator. The system is activated when the ignitionswitch is in the ON position, the headlamp switch is inthe OFF position, and the parking brake is released.What it means: The DRL "Module"does everything. It does not use a resistorbut instead uses switches to provide lower voltage tothe High beams. Not sure about to much morelike wiring, etc.All I know is that it"snot compatible with the 1999 and newer layout.I do however have the part number for the module:F65Z-15A272-AA.It"s location isaround the same area as the resistor on the 1999 andnewer trucks.
Some History of mysearch...I have spoken to the service department and partsdepartment at my local Ford Dealership (where I boughtthe truck) letting them know I wanted to enable DRL onmy 1999 Ford F150 truck.I was told thatthis could be done by purchasing the DRL Kit for about$55.00.I did just that and found that Iwould have to hack into my wiring harness to get this towork.I checked my shop manual and found thetruck is already wired for DRL.I"m making anassumption that this is because Canada requires DRL andFord does not want to have 2 wiring harnesses for thesame truck. So I checked my truck and sure enough,the wiring harnesses are there and all I needed to do isreplace the loop-backplug with the DRL Relay Block and install the DRLResistor into it"s location.Ford enables DRL on Canada trucks simply by pluggingin a DRL Relay Block and plugging in a DRL Resistor.On American trucks without DRL, the wiring harness is the same but they simply replace the DRL Relay Blockwith a loop-backplug and put a cap on the wiring harness where theDRL Resistor plugs in.The loop-backplug provides ground to the Multifunction Switch(Steering Column High/Low/Flash to Pass switch) so thelights still work when the DRL Relay Block is notpresent. On trucks sold without DRL the DRL Relayblock is not present, so the resistor doesn"t even needto be plugged in... thus the cap. So for peoplewanting to disable DRL on their trucks, all they need todo is remove or unplug the resistor.
I want toDisable DRL on my Truck...This is actually very easy.You need to findthe resistor (See Location is Everything below)and disconnect it. It"s that easy. AndYes... your low beam and high beams will stillwork with the resistor unplugged. :)
I want to EnableDRL for my Truck...So you want DRL for your truck but don"t want to go outand get the electrical engineering degree needed toinstall the Ford DRL "Kit"?Well... you can enable DRL for your truck withouthacking into your wiring harness. Use this site toget locations and part numbers for doing this.There is another good web site out there to help youwith this task.See the Other DRL WebSite links below.
Location isEverything!Finding this stuff seemsto be the greatest challenge for everyone.Here is where everything is located on my truck.
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DRL Resistor/Cap:The DRL Resistor (or where it"s supposed to be) islocated in the front of the truck.Clickfor DiagramsDRL Relay Block/DRL Loop-Back Plug:The DRL Relay Block is located just under the top of thepassenger side dash. Clickfor Diagrams
Part Numbers:1999 and newer:The part numbers depend on the year of truck youhave.What I have seen is that Below are thepart numbers of the Relay Block and the Resistor: (Thebattery and penny give you an idea of size)
Relay Block (Shown Left) - Ford Part Number YL1Z-13B218-AAResistor (Shown Right) - Ford Part Number XL3Z-14A601-AACost of the relay block is about $45.00 and the resistoris about $15.00. So for about $65.00 (includingshipping) you can plug in these parts and have DRL onyour truck. :)
1998 and older:
DRL Module - Ford Part Number F65Z-15A272-AA
Contacting Me!You can email me at
Disclaimer:(Sorry... I have to get legal for a minute)What you do to your truck/car is yourbusiness not mine. I am not responsible for damagecaused by you or someone else to you or your vehicle byfollowing any or all of these pages.Use atyour own risk! Work on your vehicle at your ownrisk.All the component location views and wiringdiagrams are from the 1999 F-150/250 Shop and WiringDiagram Manuals distributed by HelmIncorporated.(I would recommend ANYONEdoing work on their vehicle to get the shop manual...not cheap but they are good! You can even get themon CD!)