"Twilight Sentinel" Repair Information for Your Imperial

Imperial Home Page -> Repair -> Accessories -> Twilight Sentinel

Question from Allen (1969):

My twilight sentinel was broken off on the dash - a new-to-me used unit is on the way - but he tells me that the wiring diagram he is using was from an Imp that did not have this option. The box of tricks is intact under the dash, and he says there are 10 or 12 wires in good shape coming into/from that, apparently spliced into something [the headlamps...?]

Does anyone out there have the wiring diagram for the 69 Imp. specific to the twilight sentinel - that you could attach to an email and send to me, to send to him? [He doesn't have a fax :(] If a wiring diagram is something we can buy from someone out there, just sing out!

Is there a different option than Twilight sentinel that automatically dims your headlights for an oncoming car, where is this photodiode located/wired?

Reply from Dick:

The unit that sticks up above the dash for the twilight sentinel sensor only has two wires, one gray, one black and you can't hurt it by hooking it up backwards if you can't figure out which way it originally went. If you hook it up and the lights won't come on, reverse it.

The automatic headlight dimmer is a much different animal. On 68's, they are a separate option, not sure about the 69.

I have a 69 manual, I can scan and send you the appropriate page, but be forewarned, it will be a BIIIIG file! If all you have is the twilight sentinel, you really don't have a big problem hooking up your sensor. If you have the whole enchilada, you'd better get a manual.

If your mechanic has any 69 Chrysler manual, it should show these features. Tell him to look at page 8-107.

The headlight dimming sensor is a forward looking lens that is on the dashboard some years, and looking through the grille on other years. Your car is one of the latter. Look forward of the radiator mounting yoke for it.

Question from Allen (1969):

Where would I find the on dash twilight sentinel switch unit for my 1969 Imperial? It apparently says 'Early and Later' on it, but my mechanic says it is broken.


From Dick:

The twilight sensor is a simple photodiode, available at any Radio Shack for a few cents. If you have some electronic experience, or know someone who does, it is child's play to repair these - there is nothing too them at all.

From Pete:

I see that Dick has already answered this but I'd like to clarify something. This isn't a switch at all. It is, as Dick mentioned, simply a photodiode. It senses ambient light levels and works with the sentinel relay to turn on the headlamps when it gets dark. The early/late business is just a plastic disc with a hole in it that is mounted over the photodiode; turning the disc to "early" obstructs the diode opening so less light reaches it and the lights turn on sooner. Turning the disc to "late" fully opens the aperture and lets all available light in -- the lights turn on later.

Question from John (1973):

Is the Chrysler the same setup as GM uses in their Twilight Sentinel? I am curious because my 73 Imperial will turn lights off momentarily when passing under some streetlights, whereas my GM Sentinel systems have never done that. Do I have a problem with my system or is that the nature of the beast? I have tried adjusting the early/late adjuster on the dash, but it still does it sometimes.


From Dick:

It sounds to me like the capacitor which makes the circuitry take some time to make up its mind has failed, and it is making a snap decision when it sees a flash of light. They really shouldn't react that fast. Of course, where I live, I never see a streetlight. Without a schematic, I couldn't go any further with a diagnosis. I have a suspicion all brands of cars used the same system, but that is only a guess.

From Pete:

You have a problem with your system. The lights shouldn't turn off when you pass under a street light. The amplifier has a time delay circuit to prevent this, and also prevent the lights from turning on when you pass through a short tunnel or underpass. And yes, I believe the system is the same as the GM version. Also the auto-dimmer set-up. In fact, I'm pretty sure that I have the auto-dimmer photocell from a Cadillac in my 70 LeBaron. I did a side by side comparison and found them to be identical.

From Dan:

The Imperial sentinel uses a sensor that sits on the dash pointing straight up. The GM products I've owned have all faced forward.

Tip from Dick:

The twilight sentinel also lights your backup lights, so you can stumble your way around the trash cans in your driveway at night without falling in. By the way, I notice that Saab lights the cornering lights too, when the twilight sentinel is lighting your way to the house at night. Neat idea.

Addition from John:

Imperials will also light one cornering light with twilight sentinel if you have the turn signal switched on as you depart the car.

Tip from Chris:

The twilight sentinel's automatic operation is manually overridden by pulling the headlamp switch out. In other words, pulling the switch fully out would turn the headlamps on regardless of where the sentinel's light sensor was adjusted (barring a malfunction). Only when the headlamps are manually switched off does the automatic sentinel take over.

Tip from Chris:

No, Safeguard Sentinel was what GM calls Twilight Sentinel and Ford calls Autolamp. It included an ambient light sensor on the dash in '67, outside on the cowl near where the wipers park in '68, and it would automatically turn the headlamps on and off at dusk and dawn. I believe you needed to have Safeguard Sentinel in order to add the related headlamp beam changer, which sensed oncoming headlights and dipped the headlamps from high beam to low beam in response, then automatically put them back to high beam once the vehicle passed. I don't see any such connection listed in my materials, but I've never seen a car with beam changer but without Safeguard Sentinel.

Interestingly, it was one of those options that was available on the '75 Imperial but died during the 1976-78 NYB run.

To make matters more confusing, there was also the Sentry Signal, which was essentially the master "Check Gages" [sic] warning light. After 1966, it was not labeled on the dash as such, but the marketing materials still called in Sentry Signal.

Addition from Dick:

My 68 has the Safeguard Sentinel Lighting option (which was mandatory with the Automatic Headlight Dimmer option) but does not have the Dimmer. The ambient light sensor is mounted inside the car on the dash above the driver's left knee, about 2 inches back from the windshield. Perhaps this sensor was incorporated in the dimmer sensor when the car was thus equipped, but when it is solo, it's on the dash just like your 67, I'll bet.

For those who have non-functioning sensors (symptom is that the lights never go off), I posted a procedure to follow to repair the sensor with a $1.98 photodiode from Radio Shack, it will be in the IML archives somewhere, probably back in 98 or 97.

The Mopar version of the "Twilight Sentinel" one-ups the GM version, by the way, by also illuminating the backup lights, so your way is illuminated even if you walk in the area behind your car. I thought that was pretty trick, until I noticed that late model SAABs even turn on the cornering lights with it! (Easy feature to add to our Imperials, if it's worth the trouble.)

Question from Paul (1975):

My '75 Newport has it (the headlight switch says 'Sentinel Delay' on it and the little thing on the dash) and it doesn't work right (the headlights are always on regardless of lighting conditions) --- It even works without the thing on the dash, I've swapped my '75 panel (center speaker griil) with my '78 panel (stereo speaker grills) and my '78 doesn't have it.


From Chris:

I'm confused. You say it doesn't work right but then that it does work even with the light sensor removed. It would seem that removing the light sensor by swapping the dash panel from a '78 (when Sentinel was no longer offered, sadly for me) is the reason your lights are on all the time. The delay feature would work regardless of the light sensor, because it merely leaves the lights on after the car is shut off anytime the car is turned off while the lights are still on. Since yours are always on, they presumably always stay on for the interval.

I believe the light sensor is a "normally closed" circuit, and that sensing light causes the sensor to open (or break) the circuit and thereby turn the lights off. Even though the consumer benefit of the device is to turn the lights on in darkness, I think it actually functions by turning them OFF in daylight.

Easy way to diagnose this: think of them as light-sensing auto-off headlamps, not darkness-sensing auto-on!

From Dick:

That's right, Chris, the action of the sensor is to turn off the lights when it detects sufficient ambient light, if the key is on.

It is not strictly speaking a switch, however, it is a variable resistance photodiode, which drops in resistance when it "sees" light. It is connected to a resistance level sensing circuit, which "trips" the lights off when a threshold is reached. This makes the device very easy to repair, at least if the failure is the most common one, namely failure of the photodiode. These are dirt cheap, and in fact come in an assortment package for a few bucks from Radio Shack. I think the threshold resistance is somewhere around 500 ohms, so pick one from the assortment which shows a "dark" resistance of 1500 Ohms or so, then use the variable lens cover to adjust it so that the lights come on at dusk. I did this 14 years ago when I first got my 68, and it still works perfectly.

Question from David (1965):

I want to post a problem I am having with my 65 LeBaron. My car's auto dimmers will not respond to the manual switch in the floor. Except for that the dimmer system works correctly. I have replaced the switch in the floor but this has not solved the problem. This is an original unmolested car so I feel confident when I state the electrical system has not be played with. Any suggestions would be greatly appreciated.

Reply from Dick:

I don't have access to a schematic of the system, but from your symptoms, I'd check the wiring from the floor switch to the control box for the SS system. It appears that the control box doesn't know you are changing the setting of the floor switch. If you have the FSM, you should be able to buzz out each wire individually to make sure all is connected properly.

Just to nit pick a little, I think you are asking about the Automatic Headlight dimmer option, not just the Safeguard Sentinel option.

Question from Michael (1968):

As the sun set this evening a co-worker noticed that my marker lights (dunno what they're called, the rectangular ones set into the bumper) were on. No changes of the regular headlight switch or the sentinel (automatic highbeam dimmer) will turn them off. For the heck of it, I even played with the dash/interior lights. I suspect either a bad switch in the light circuitry or in the photovoltaic cell in the sentinel sensor. Does anyone have an idea what's wrong? For now, I unplug the battery and anxiously await your learned responses.


From Dick:

The Twilight Sentinel is independent of the "Automatic Highbeam Dimmer". These are two separate accessories, although the latter requires the former as a prerequisite. ( and I haven't a clue why ONLY the front parking lights would stay on- must be a failed headlight switch or a short in the wiring between a live wire and the lead to the front parking lights ).

From John:

Imperials will also light one cornering light with twilight sentinel if you have the turn signal switched on as you depart the car.

Question from Steve (1968):

Does anybody have the correct part number for the '68 headlight switch? Is the switch the same with cornering lamps? Are '67 and '68 switches the same?

Reply from Bill:

There is a variety of numbers for both years. The cornering lights don't make a difference but the Sentinel and Auto Dimmer options do. Here is what I have. These are original part numbers and probably have been updated but your Mopar dealer should be able to find them from these.


Standard=2809048 w/Sentinel Delay=2820562


Standard=2809048 (same as 67) w/Sentinel=2864286 w/Sentinel & Dim=2864283

Question from Erik (1967):

My new Imperial has no headlights, tail lights, or dash lights. I assume this is the headlight switch. I went to every parts house in the Eugene-Springfield area today, trying to find one, but no luck. Where should I look? Will switches from any other year or make interchange with the 67?? Thanks for your input.


From Dick:

It could indeed be the switch, but if it is, it can be repaired. If you are not comfortable doing it yourself, there are others on the list that will repair it for you (myself included).

But, before you go to all that trouble, check to see that your twilight sentinel (if equipped) is not causing the trouble, and that the circuit breaker is not open. If you have an FSM, these parts will be easy to check. If you don't, I'd advise getting one. These cars are very complicated electrically, it is virtually impossible to repair them without a manual.

From John:

I had this problem on a 60 & it turned out to be the high beam switch was bad.

From Chris:

I'd suspect a couple of fuses (or simply a disconnected headlamp switch) before I sought out a replacement switch (which, by the way, can be from a '67 or '68 Imperial but nothing else). It is odd that all those functions would go out together (and unlikely that the previous owner let all of them fail one at a time).

The switch is fairly easy to get at. You need to remove the instrument cluster, which means about ten screws, disconnecting the cable behind the speedometer, and unplugging a few connectors. Once it's out, I'd remove the headlamp switch from the instrument panel and reconnect it, checking for loose or dirty connectors and jumping the wires to see if bypassing the switch illuminates the lights (sorry, don't have the schematic handy but I could get a copy of it to you in a few days if needed... I recommend buying a factory service manual).

If you have twilight sentinel, this could be the culprit, too.

And I'm sure one of our vendors on the website (Bob Hoffmeister, Murray Park, etc.) can find you a switch if you end up needing one.

From Ron:

Your choices are either 1967 or 1968 Imperial and several years of Chryslers "C" body switches. 1967 and 1968 Chryslers, Plymouth and Dodges also used the same type flip switch for the headlights. Obviously, these are more common in the salvage yards.\

From Bill:

A switch from a 68 will fit a 67. Does your car have the auto dim and the sentinel? If so, this might be your problem.

This page was last updated on December 1, 2001. Send us your feedback, and come join the Imperial Mailing List - Online Car Club