Originally Posted by Sonartech

I don't personally like DRL's so I wanted to disable them, but I also wanted the option of easily re-enabling them if necessary. For my solution, I decided to install a round flush-mount switch on the bottom of the relay housing itself (the part that detaches from the bottom and pulls away from the wiring harness). The relay housing plastic is soft and very easy to cut. After pushing the switch in to the new hole and positioning it so that the wires going to the switch are closest to the outside edge (to clear the wires going to the bottom of the relays), I cut the primary white & black wire equidistant and stripped & tinned both ends. The flush mount switch only protrudes into the bottom of the fuse box by abour 1/2" to 3/4" of an inch - plenty of room.

Next, I used some white wire I had of the same gauge and soldered two 6-inch lengths to the switch. I used adhesive-lined heat-shrink tubing to seal the soldering work. I then stripped & tinned the other ends of these wires. Next, I soldered one of the white wires coming from the switch to the end of the wire I cut from the original wire that had the matching female spade terminal (the part that snaps in place inside the relay box). I used heat shrink tubing to seal this splice as well. (You can actually do this soldering away from the car because the female spade terminal presses-in from the bottom of the relay block making it very easy to reattach later.)

Finally, I soldered the remaining free white wire from the switch to the white & black end that goes into the wiring harness loom and sealed it with heat shrink tubing. I then took the female spade terminal and pushed it back into its position in the relay connector until it clicked (locked) in place. I folded the wires into the box and snapped the relay fuse box bottom back onto the center base of the relay box, re-installed the fuses, tested the lights and reassembled the housing in the engine.

The result was awesome. The switch is out of the way and yet easy to get to if necessary and virtually invisble. If you ever had a light problem and needed Lexus to troubleshoot it, they would never even know this tiny switch was there because it's small, flush-mounted and virtually invisible from the top.

You might consider this kind of solution if you don't have a need to activate/disable the DRL's from inside the car.

The only small problem this solution has is that you will have to take off the plastic engine housing covering the relay box to be able to get to the switch - but that's it!

Let me know if you need more guidance than I provided here. Also, thanks very much to TKRussell for the original, very detailed instructions. If you're not a technical writer, you should be :-)

Sonartech
Monroe, WA

Originally Posted by srashid

Thanks Sonartech, sounds like a good solution if you need to get the DRLs working again easily, but if I tried that I think I might set fire to the engine compartment

As I said in an earlier post I just snipped the wire and put tape on the ends, but it can be easily reversed with one of those tiny sleeve connectors if required. By the way I agree tkrussell should be a technical writer.

Anybody else had an of issue of driving at night without lights? Because of the way the instruments are permanently lit up, I have forgotten to switch the headlights on a few times.

Originally Posted by tkrussell

How-to Instructions for Disabling the Daytime Running Lights (DRL)
on RX 330 and RX350.

The process is completely reversible, and causes no result other than disabling the DRL.
It should take about 30 minutes to complete.

Unlike some Lexus models, the RX 330/ 350 /400 does not have a software switch to disable DRL in the Lexus personalized Settings (LPS).

Disclaimer: Although these instructions have been demonstrated to work well on the RX330, use of the information is AT YOUR OWN RISK. I am unaware of any legal or contractual sanctions incurred by disabling the DRL in the USA, but again, you should check your State Laws (or other country laws) before proceeding.

Background: The DRL works by running 12v current through BOTH High Beams in series, producing a low intensity light. In essence, each 12v bulb sees only 6v. DRL is switched to be on whenever Low or High Beam headlamps are off and the engine is running with the parking brake off. The headlamp system uses 5 fuses and 5 relays to control everything.

DRL is disabled by interrupting the ground circuit of the DRL series current. Removing the "DRL" fuse or a "DRL" relay will also disable the RH High Beam, or worse, depending on the relay removed.

Tools Required:
Small Screwdriver. Electricians Tape, Miniature Screwdriver 0.070" or a 1/8" wide by 0.050 thick flat metal shim about the size of a shirt collar stay.

Procedure:
1) Make sure everything is working to begin with. Start the engine, release the parking brake, and with the headlamps to "Off", make sure both high beams are ON at low intensity.
Turn the switch to "Parking Lights". 2 small bulbs above the High Beams should also come on, as well as the tail lamps. Turn the switch to "Headlamps". The Low beams should come On, and the low intensity High beams should turn Off. Note that the 2 small bulbs in the High Beam housing are still On (these are the front Parking Lights) Toggle the Dimmer to High Beams. The High Beams should both come on at Full intensity. Now turn Lights and Engine Off.

2) Open the Hood. Remove the Black Panel covering the Right Side (of the car) Engine Compartment (4 fasteners). Push the fastener center dot to release. DO NOT lose the fasteners in the engine bowels! Set the fasteners aside, and remove the cover and set aside.

3) On the Right Inner Fender is a rectangular Black Box labeled "Relay". Open the top by using a small screwdriver to gently pry the end locks. Set the top aside. Inside are 2 Relays.

4) Remove the FRONT Relay by gently pulling it out. Note that it has 5 Contacts. 3 in a Row, and 2 on the other side. Set it aside.

5) Restart the engine. Confirm that the DRL are off. Turn on the Headlamps and Toggle the High Beam. Confirm that the LH High Beam is ON, and the RH High Beam is OFF. This insures that you at the correct Relay. Turn the Engine and Lights Off.

6) Gently Remove the Other Relay from the Box as well, and set it aside. It has a different Prong configuration. Gently pull the Relay Box up and off of its mounting. Gently extend the Wiring Harness leading to it to give yourself some slack.

7) Open the Bottom of the Relay Box by gently Prying the locks. It will pivot open on one edge.
Turn the entire Relay Box over to see the Wiring inside.

8) The Front Relay has 5 wires leading to it. Orange, Turquoise, Blue, and 2 White/Black Stripe.
Note that Turquoise , Blue, and 1 White/Black Stripe are Thicker in Diameter. The Orange and the other White/Black Stripe are thinner.

9) Find the Thicker White/Black Stripe Wire. It should lead to the Center Contact of the 3 in a Row set. THIS IS YOUR TARGET.

10) For a permanent fix, you can cut the wire. I HIGHLY recommend you proceed in a reversible fashion. This way you or the next owner can reinstate the DRL easily.

11) Turn the Relay Box upright. To remove the Center Contact of the 3 in a Row, use the Miniature Screwdriver or the Metal Shim to Release the locking Pin of the Contact. This is the only tricky part, and is easy after you have done it once and can see how the Contact locks in place.

12) Look at the Contact from above. It has a Flat side, and a Rounded Side. Slide the Shim or Miniature Screwdriver down the Middle of the Rounded Side against the plastic. Stay in the Middle, You will meet an obstruction (the locking Pin). Push the screwdriver or shim through and GENTLY pull the thicker White/Black Stripe wire from the backside. The wire and Contact should come out of the Box. If it does not, repeat the process. It does NOT take Brute Force.

13) With the Contact free of the Housing, wrap the metal with electricians tape for insulation.
Fold the wire into the Relay Box, and Close the Bottom. Make sure both sides snap in place.
Reset the Relay Box in its Mounting on the Inner Fender.

14) Replace both Relays, pushing them firmly in place. The Front Relay is still needed for the RH High Beam. Replace the Relay Box Cover, making sure both ends snap in place.

15) Replace the Right Engine Cover and 4 fasteners. To Reset the Fasteners, Gently separate the 2 legs until the center Dot can be pushed back up from the bottom to a protruding postion. This is also tricky until you have done it once. Just be gentle. With the Dots protruding, insert the fastener and click the Dot down part way. This will lock the Engine Cover in place.

16) Start the Engine. The DRL should be Off. Go through all positions of the Light Switch and Dimmer to make sure both Low and High Beams on L and R sides come On as they should.

That's it. Make sure you have retrieved all your tools from the Engine Compartment, close the Hood, and enjoy your work.

This Process should work on all US RX 330, RX350, and RX400, in that the Headlight wiring is the same. It will work on Standard and Xenon Low Beams. Please let me know if you discover any Kinks. I have looked only at US wiring diagrams, so I cannot say with certainty if things are the same in Canada, Europe, and Asia.

Note that I have repeatedly used the word "Gently" Plastic will break, and new Lexus parts are expensive.

It's a pleasure to give back to the Forum.

Originally Posted by mandyfig

You do have the "bulb" light on which is green to alert you that lights are on...did you ever notice?

Originally Posted by jay2010

I've the 2010 RX 350. I want to disable the "DRL Off" switch, in other words I want the DRL's ON all the time and remove any option to turn them off.
Can anybody please help me with this ?????