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Car Forum / Lexus Cars / July 2005Automatic headlights RX 300
I have a 99 Rx 300 and just noticed that my headlights no longer work when in the automatic position. Does anyone out there know if this if just a blown fuse or what? > I have a 99 Rx 300 and just noticed that my headlights no longer work when > in the automatic position. Does anyone out there know if this if just a > blown > fuse or what? 5 possibilities: Check the dome light fuse (may be in the fuse box under the hood) Check the ign/gauge fuse (may be in the fuse box under the instrument panel Check the light sensor on the dashboard Check the courtesy light switches in the doors (hint - if the dome light comes on with the doors closed, the switch is shorted) Check the system wiring harness - you'll need a wiring diagram and multi-meter to do this.  SignatureRay O correct the return address punctuation to reply Ok thanks, I will check these things, it seems like to me everything else is working ok, dome lights etc. What do you mean by the light sensor on the dashboard? >> I have a 99 Rx 300 and just noticed that my headlights no longer work when >> in the automatic position. Does anyone out there know if this if just a [quoted text clipped - 10 lines] >Check the system wiring harness - you'll need a wiring diagram and >multi-meter to do this. > Ok thanks, I will check these things, it seems like to me everything else > is > working ok, dome lights etc. What do you mean by the light sensor on the > dashboard? The light sensor is actually easier to see from outside the vehicle than from inside. There will be 2 or 3 light sensors that look like black dome-shaped buttons, probably in line with the front defroster vents. The one on the passenger side is probably for the automatic AC, and the one on the driver's side is for the auto headlights and if there is a 3rd one on the dash somewhere, it is for controlling the digital/map display. The light sensor is just a photoelectric eye that acts as a switch. When the sun shines on the one for the auutomatic AC, it will kick up a notch. If you put something over the sensor for the headlights, the lights should come on. To check the switch, you have to pop it out and check the continuity. SignatureRay O correct the return address punctuation to reply >>> I have a 99 Rx 300 and just noticed that my headlights no longer work >>> when [quoted text clipped - 12 lines] >>Check the system wiring harness - you'll need a wiring diagram and >>multi-meter to do this. Oh ok, I know what the light sensors are now, one more question, how do you pop out the switch and check for continuity? What exactly am I looking for? >> Ok thanks, I will check these things, it seems like to me everything else >> is [quoted text clipped - 20 lines] >>>Check the system wiring harness - you'll need a wiring diagram and >>>multi-meter to do this. > Oh ok, I know what the light sensors are now, one more question, how do > you > pop out the switch and check for continuity? What exactly am I looking > for? I've never had to remove one so I'll have to take a look at a manual tonight. My guess is that you can just pry it out but let me check before I give you bad advice. There may be a way to check at a harness connection without having to physically remove the sensor. As far as checking for continuity, you will need a multi-meter or continuity checker. If you remember your grade-school science classes where you used a battery, a bulb or buzzer, a switch, and some wires to make a circuit. When you close the switch, you complete the circuit and make the bulb or buzzer work. Closing the switch means there is a continuous loop from the power source to the device and back to the power source. A photocell is basically a switch. When a light shines on the cell, the switch closes. Checking for continuity means you are checking for a continuous circuit. When a properly functioning switch is closed, you will have continuity from one terminal on the switch to the other. If you have a voltage tester, you can see if there is voltage at both terminals when the switch is closed but then you're wading through a big thick wire harness to find the correct wire, which is time consuming unless you have a wiring diagram. SignatureRay O correct the return address punctuation to reply >>> Ok thanks, I will check these things, it seems like to me everything >>> else [quoted text clipped - 23 lines] >>>>Check the system wiring harness - you'll need a wiring diagram and >>>>multi-meter to do this. Wow, this sounds way too complicated for me. Basically I just don't want to pay big bucks for a diagnosis, can an auto electric shop check this out for me? >> Oh ok, I know what the light sensors are now, one more question, how do >> you [quoted text clipped - 31 lines] >>>>>Check the system wiring harness - you'll need a wiring diagram and >>>>>multi-meter to do this. > Wow, this sounds way too complicated for me. Basically I just don't want > to > pay big bucks for a diagnosis, can an auto electric shop check this out > for > me? Any competent auto service shop should be able to check the function of the photo sensor. Before you do that, check the fuses under the dashboard and under the hood. Good luck! SignatureRay O correct the return address punctuation to reply >>> Oh ok, I know what the light sensors are now, one more question, how do >>> you [quoted text clipped - 38 lines] >>>>>>Check the system wiring harness - you'll need a wiring diagram and >>>>>>multi-meter to do this. Ok, thanks, I will do that first. >> Wow, this sounds way too complicated for me. Basically I just don't want >> to [quoted text clipped - 12 lines] >>>>>>>Check the system wiring harness - you'll need a wiring diagram and >>>>>>>multi-meter to do this. |
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