automatic headlights

On my 2000 taurus sel when I leave the headlight switch in the auto on position they stay on during the day including dash lights. I'm thinking it might be the sensor on top of the dash. Would anyone know how to check this or have any other suggestions as to the cause. Thanks.

A dirty, bad or disconnected sensor would also cause this. Check your's fuses too. I'm assuming that it used to work correctly. I think you can test it with a VTVM but I don't know what range it should fall in. Also you should know that when you remove that center section of the dash that it is hard to snap back in because of the angle of the windshield. If I'm not mistaken you have to snap in the edge closest to the edge of the windshield first to put is back in.

A dirty, bad or disconnected sensor would also cause this. Check your's fuses too. I'm assuming that it used to work correctly. I think you can test it with a VTVM but I don't know what range it should fall in. Also you should know that when you remove that center section of the dash that it is hard to snap back in because of the angle of the windshield. If I'm not mistaken you have to snap in the edge closest to the edge of the windshield first to put is back in.

Wow, it can't be too easy to find a Vacuum Tube Volt Meter (VTVM) these days! :)

A standard digital multimeter (DMM) should work fine, the sunload sensor is a CDS cell that varies in resistance depending on the amount of light it registers. Unfortunately, I'm also unsure of the "good" range. You could try an assortment of completely covered, partially covered, and sunlight though to see how the resistance changes under those conditions.

I'm going to pose one of MyTaurus8AChevy's assumptions as a question, did the autolamps ever work properly since you've had the car? Is there a chance your Taurus is equipped with Daytime Running Lamps (DRL)? I'm not sure if the DRLs also turn on the dash lamps.

-Rod

I'd like to know the solution too, my 01 does the same thing. No DRL, because when the switch is in the off position, there are no headlights on. When I turn the switch to the left for "auto", it turns on the headlights, parking lights, and dash lights, regardless of light level. So I manually engage the headlights by turning to the right (mostly because you have to run them manually if you want to turn on the Fog lights, which do NOTHING, but look cool :o)

You can also test the sensor with a bright flashlight, but you'll need to leave it focused on the sensor for at least 45 seconds to be sure.

You can also test the sensor with a bright flashlight, but you'll need to leave it focused on the sensor for at least 45 seconds to be sure.

Its not that they don't turn on, they don't turn off in bright light like they should, but keep on running like its dark out. When exiting the car, they will turn off after a delay of 30 seconds or so if the switch is left in the auto position. I've been reading the service manual and there are some test procedures with a multi-meter I think i'll try. Or just grab one from the junk yard and swap the switch or sensor until it works??

Wow, it can't be too easy to find a Vacuum Tube Volt Meter (VTVM) these days! :)

A standard digital multimeter (DMM) should work fine, the sunload sensor is a CDS cell that varies in resistance depending on the amount of light it registers. Unfortunately, I'm also unsure of the "good" range. You could try an assortment of completely covered, partially covered, and sunlight though to see how the resistance changes under those conditions.

I'm going to pose one of MyTaurus8AChevy's assumptions as a question, did the autolamps ever work properly since you've had the car? Is there a chance your Taurus is equipped with Daytime Running Lamps (DRL)? I'm not sure if the DRLs also turn on the dash lamps.

-Rod
Yes I have DRL & the autolamp did function properly.When working, all that was on in the auto position during the day was the DRL. Now during the day the dash & parking lights are on. I'll try to remove the top of the dash & check the resistance with a flashlight. Also I did check the fuses & they were fine. Thanks for the suggestions.

Does your car have the Electronic Automatic Temperature Control (EATC)? If so, does it seem to work fine? The climate control uses the same photocell and amplifier as the sunload sensor.

If you have the EATC, you may be able to run the self test and see if it recognizes a fault in the photocell/amplifier circuit.

As for testing the photocell, per the service manual, as the light level increases, the sensor resistance should decrease.

-Rod

as the light level increases, the sensor resistance should decrease.

It's basically a variable diode that's controled by light input, but he'll need to know the range of variance or his measurments will be meaningless. I also wonder if the sensor is just dirty giving a false reading.

Does your car have the Electronic Automatic Temperature Control (EATC)? If so, does it seem to work fine? The climate control uses the same photocell and amplifier as the sunload sensor.

If you have the EATC, you may be able to run the self test and see if it recognizes a fault in the photocell/amplifier circuit.

As for testing the photocell, per the service manual, as the light level increases, the sensor resistance should decrease.

-Rod
Yes I do have EATC. How would I run the self test. Also the sensor gets wiped off when I clean inside the car.

Per the factory service manual:
The RCC module self-test will detect concerns in the system control functions and will display hard diagnostic trouble codes (DTCs) in addition to intermittent diagnostic trouble codes for concerns that occur during system operation. The vehicle interior temperature should be between 4°-38°C (40°-100°F) when carrying out the self-test. If the temperature is not within the specified range, false in-car temperature sensor DTCs will be displayed.
The self-test can be initiated at any time. Normal operation of the system stops when the self-test is activated.
To enter the self-test, press the OFF and floor buttons simultaneously and then press the AUTO button within two seconds. The display will show a dashed line in the center of the climate control display window of the integrated control panel (ICP).
The test may run as long as 30 seconds. Record all DTCs displayed. The self-test is completed when 888 appears in the center of the climate control display window of the ICP.
If any DTCs appear during the self-test, refer to the REMOTE CLIMATE CONTROL MODULE DIAGNOSTIC TROUBLE CODE (DTC) INDEX. Carry out the diagnostic procedure given under ACTION TO TAKE for each DTC given.
If a condition exists but no DTCs appear during the self-test, refer to the SYMPTOM CHART condition: The EATC System Is Inoperative, Intermittent or Incorrect Operation.
To exit the self-test and retain all intermittent DTCs, press the "—" (cooler) side of the TEMP button. The RCC module will exit the self-test and retain all intermittent DTCs.
To exit the self-test and clear all DTCs, press the front defrost button. All RCC module DTCs will be cleared.
Always exit the self-test before powering the system down (system turned off).
Intermittent DTCs will be deleted after 80 ignition switch ON cycles after the intermittent condition occurs.Per the code chart (which won't paste in here well) there are two codes for the Solar Radiation Sensor that are part of the self test.

-Rod

Shorod thanks for the help.

I ran the RCC module self test & got code 051, what does this mean. I let it run for 2 min & all it flashed was 051 it never flashed 888 to say the test was completed, so I exited the test retaining the DTCs.

I think you're on to something here. According to the service manual, Self Test Fault 051 means "Solar Radiation Sensor Open."

There is a pinpoint test to check the condition of the sensor. If you'd like a PDF version of the test, send me a private message with the request and an e-mail address for you that can accept PDF attachments. The procedure has diagrams which will not paste well here.

-Rod

I think you're on to something here. According to the service manual, Self Test Fault 051 means "Solar Radiation Sensor Open."

There is a pinpoint test to check the condition of the sensor. If you'd like a PDF version of the test, send me a private message with the request and an e-mail address for you that can accept PDF attachments. The procedure has diagrams which will not paste well here.

-Rod
PM sent

Large attachment sent which covers all diagnostics for the EATC.

Good luck!

-Rod