notch8 Posted June 28, 2008 Report Share Posted June 28, 2008 Hey guys Ground Rules: 1996 base Eldo, 1997 FSM to work with. Headlamp automatic turn on by the twilight sentinel is NOT happening. Headlamps work normally using the manual headlight switch (knob). I believe this problem to be intermittant for the last 4-6 weeks. I started the car a week ago, after dark-no exterior lights at all-I slid the twilight switch back & forth a few times & it worked correctly, ex. lights come on, had delayed shut off-everything's good. I'm thinking DIRTY switch. This evening, dark, TS sw. @ mininum position-no headlights. Play with TS sw.-nothing, no headlights. Pull manual knob out-fine, headlights on. According to the FSM, I'm failing at step #7 of the headlamp system check (pg 8A-100-12). Pg 8A-100-13 directs me to chart#6, pg 8A-100-21. Chart#6 says I need a scan tool to check the Instrument Panel Cluster (IPC) input; twilight switch. I don't have a scan tool. From reading the FSM it's either: a bad ambient light sensor, a bad IPC, a bad headlight switch or a short or open in the associated wiring. Anybody got any ideas that doesn't include an expensive scan tool? Thanks Roger Link to comment Share on other sites More sharing options...
WarrenJ Posted June 28, 2008 Report Share Posted June 28, 2008 Working with a 1997 FSM always leaves you wondering if you have an accurate drawing to work from. I've attached the 1996 headlamp drawing (from an after market manual) so you won't have that worry. I would place an opaque cover over the TS photocell on the defroster vent and see if the simulated TOTAL darkness might get the TS to "kick in." If that gets the job done it's likely the photocell is marginal. The photocell is inexpensive (as I recall) and is ridiculously easy to change: pry the defroster vent up and turn the photocell 1/4 turn to remove it from the vent grill. My '95 FSM (again, the wrong manual) says a photocell resistance greater than 90k ohms is interpreted as nighttime and a resistance less than 70k ohms is interpreted as daytime. YMMV. Another thing I would try is removing the headlamp switch and re-seating all electrical connectors including separating the TS module from the rear of the headlamp switch and re-seating it also. The headlamp switch uses skin locks to attach it to the soft dash material. Simply pull it CAREFULLY towards you to remove it from the dash (an alternative is to push it out from behind. Is there a removable end cap at the left of your dash?). After that you pretty much need a Scan Tool unless you want to tear into the dash and troubleshoot it with a DVOM. Regards, Warren EDIT: My guess is that disconnecting the photocell, presenting a resistance far greater than 90k ohms, would tell the IPC, "Hey! It's nighttime; turn the lights on already." I don't have firsthand experience with this. 96EldoradoHeadlamps.pdf There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
Logan Posted June 28, 2008 Report Share Posted June 28, 2008 The photocells are known for shifting their calibration. I had one, worked ok until I drove past the mall. Overhead lights would turn off the headlamps...thinking it was day light. Replace the photosensor. Logan Diagnostic LLC www.airbagcrash.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
Texas Jim Posted June 28, 2008 Report Share Posted June 28, 2008 A agree with the photosensor opinion. The one on my DTS turns "ON" the lights before it gets dark and in the winter time it does not turn "OFF" till about 9 or 10AM or so. Link to comment Share on other sites More sharing options...
notch8 Posted June 28, 2008 Author Report Share Posted June 28, 2008 Thanks guys for the great advice, as usual. Warren, the drawing is great-thanks! No, the car does not have an end cap, looks to be 1 piece. Don't see any screws around the defroster vent-I'll try to gently pry it out, remove the sensor, check it's resistance in light & dark and go from there. I'll keep you posted. Thanks Roger I suppose the sensor is a "dealer" only item. Link to comment Share on other sites More sharing options...
WarrenJ Posted June 28, 2008 Report Share Posted June 28, 2008 I suppose the sensor is a "dealer" only item. Yes, but cheap. Regards, Warren There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 28, 2008 Report Share Posted June 28, 2008 Thanks guys for the great advice, as usual. Warren, the drawing is great-thanks! No, the car does not have an end cap, looks to be 1 piece. Don't see any screws around the defroster vent-I'll try to gently pry it out, remove the sensor, check it's resistance in light & dark and go from there. I'll keep you posted. Thanks Roger I suppose the sensor is a "dealer" only item. On my 96 the defroster vent / speaker cover prys up. I just looked at my 96 manual, it looks like you have a defroster grill that prys up. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
notch8 Posted June 28, 2008 Author Report Share Posted June 28, 2008 Ok guys, pryed defroster grille out-very easy job, untwisted both sensors, removed ambient light sensor (as Warren suggested) turned key on-headlights came on (low beams) as he predicted, turned key off, lights went off after short delay. Hooked sensor up to DVOM - max. ohms.=31K with my hand over it! It thinks it's ALWAYS light outside= bad sensor! Warren, Logan & everybody else- you guys are GREAT-you hit it right on the head-the first time!!!!! As soon as I was positive the sensor was bad, my wife (her car) said "CALL NAPA" LOL LOL LOL. I knew the dealers were closed by then. Of course, it's a dealer item. I took the eye (sensor) out of it's blue plastic holder, the PN is 21K1382 9520. So far I can't find a match on the web or NTE's site. It's just a little photoeye about 5/16 to 3/8 in diameter with 2 leads that bend over the holder and the whole thing pushes into the socket just like a marker light bulb. If a correct value replacement could be found at RS or somewhere, it would be easy to change it out. I'll try the dealer Monday. Again, thanks guys Roger Link to comment Share on other sites More sharing options...
WarrenJ Posted June 28, 2008 Report Share Posted June 28, 2008 If a correct value replacement could be found at RS or somewhere, it would be easy to change it out. I'll try the dealer Monday. DEALER!!! Glad it worked out (we hope). Regards, Warren There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
notch8 Posted June 28, 2008 Author Report Share Posted June 28, 2008 Called local dealer, still open to my suprise, new sensor is $59.23 + tax. Not what I'd call cheap. GMDirect's price-$29.27+shipping+whatever, never bought from them before. Think I'll take my DVOM & head for the junkyard! GM PN: 25673037 Ambient Light Sensor, anybody find one cheaper-sing out! Thanks Roger Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 28, 2008 Report Share Posted June 28, 2008 That is what I did, last year, my sensor was shifted so that the system thought it was always NIGHT TIME. I went to the junk yard got about 10 and went home and tested them. They all had different readings, I chose one, but its acting up again. I need to take a look at it again. Have fun, and bring some hand tools Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
notch8 Posted June 28, 2008 Author Report Share Posted June 28, 2008 Thanks Mike-will do! Roger Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.