Lights quit coming on automatically. I replaced optical sensor under the defroster vent but no help. There is surely a control module this sensor feeds a signal to, but where is it? Lights work fine when operated from dash panel switch. Thank you, Dave
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sounds like there is a short somewhere. you need to start checking things with a multi meter, could be a bad switch. I would recommend picking up a factory service manual for your vehicle off of ebay. If you need any further assistance let me know. Thanks, lee
It's probably the lighting control module , but without doing some electrical testing that is just a guess !
Battery positive voltage (B+) is applied at all times to the lamp control module (LCM) through the underhood junction block HDLP MaxiFuse® and CKT 1242 (RED).
When you place the headlamp switch in the HEAD position, the headlamps input to the LCM is grounded. The LCM then applies battery positive voltage (B+) through the underhood junction block HDLOBML fuse and HDLOBMR fuse, which feed the left low beam headlamp and the right low beam headlamp respectively. When you activate the headlamp dimmer switch by pulling on the multifunction lever until the switch clicks, CKT 524 (PPL) is grounded to the LCM. The LCM then removes battery positive voltage (B+) from the low beam headlamps and supplies battery positive voltage (B+) through the underhood junction block HDHIBML fuse and HDHIBMR fuse, which feed the left high beam headlamp and the right high beam headlamp respectively.
Twilight Sentinel Circuit Description
Twilight sentinel determines whether the daytime running lamps (DRL), or the exterior lamps and the low beam headlamps at full intensity should be on based upon the signal of the ambient light sensor. When the ambient light sensor detects daytime, the twilight sentinel turns on the DRL. When the ambient light sensor detects darkness, the twilight sentinel turns on the exterior lamps and the low beam headlamps at full intensity. The twilight sentinel also keeps the lamps on for a delay period of 3 to 180 seconds under the following conditions:
• The vehicle is in PARK.
• The ambient light sensor detects darkness.
• The ignition switch is turned to the OFF position.
You may turn off the twilight sentinel manually. When it is dark and the gear selector is in PARK, pushing the twilight sentinel switch to OFF will turn off the headlamps and exterior lamps. Pushing the twilight sentinel switch to OFF again will turn on the headlamps and the exterior lamps. If the gear selector is not in PARK, pushing the twilight sentinel switch will have no effect.
The F- switch is just an input from the LCM - lamp control module .
Do you know how to test control module inputs an outputs ? Very easy to fry a module if you don't know how to do it .
Also have a full scan of all modules on the vehicle , could have DTC'S - diagnostic trouble codes stored . Not for the OBD 2 engine computer . The instrument cluster , BCM , LCM can all set codes too, related to lighting an someother thing's . ECM Inputs and Outputs Diagnosis
You can find free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model and engine ! Under system click on lighting ,then under subsystem click headlamps . Click the search button then the blue link . The first diagram you will see at the top the power supply to the LCM , down a little you will see the headlamp switch , ambient light sensor . Now if you want to start replacing thing's without testing good luck !
I have a 1997 cadillac deville that has both 'daytime running lamps' when put into gear and 'twilight sentinel' which turns the headlamps and parking lamps on at night, and goes off during the day or when it is bright enough.
There is an adjustable delay for the twilight sentinel to turn the headlights off after the ignition key is removed and it is night time.
I had the 'daytime running lamps' installed on a 1990 Cadillac Deville that turns the headlamps only on when the ignition key is switched to on with an aftermarket module. The headlamps are about 70% or so as bright as the regular twiilight sentinel headlamps and parking lights and are designed to go on during the day.
The twilight sentinel overrides this feature when it gets dark outside.
I had the daytime running lamps installed by an auto electric shop that specializes in electrical systems, alarms, stereos, etc.
Sounds like the problem lies in the TWILIGHT SENTINEL AMPLIFIER unit. Connected with the dash twilight sensitivity panel. All part of the electrical circuitry. Definitely a pricey component. Hope this helps.
There is a relay under the dash, on a fuse block with a black plastic cover. Usually the cover is labeled "Fuse and relay center" or "Power and relay center". Inside you'll find several large blade style fuses and quite a few relays. There are normally two or three relays associated with your lighting. In many mid nineties and up GM products, you have a relay for rear lighting, one for front lighting, and a separate relay labeled "DRM" or "DRL". You're looking for that one. This is the daytime running light relay. Odds are that relay has burnt out and needs replaced.
Check your fuses first. In a '92 Roadmaster, they would be number 14 and 15, light blue 15A fuses. I am not sure about other years, but your owners manual should tell you. Otherwise it could be the headlight switch, or the Twilight Sentinel Module if your car has the option. I had a similar problem a few months ago with my '92 Roadmaster Wagon. My problem was due to the Twilight Sentinel Module. If your parking lights do not come on (dash lights, too), but the headlights do when your Twilight Sentinel should turn them all on, try to use the rocker switch to turn on the lights. If the parking lights come on with the rocker switch, I believe you need a Twilight Sentinel Module. However, if you do not have a Twilight Sentinel Module, or your lights do not come on using the rocker switch, you may have a bad switch or faulty wiring. The Twilight Sentinel Module is located way up under the dash, to the right (passenger) side of the steering column where the column goes through the firewall. It looks like the one in the picture, and could be off white or gray, or perhaps a different color.