Output light dimming and brightening

Interior Lights Dimming Circuit Description
VF Displays
When the ignition switch is in the RUN position, the instrument cluster activates its VF display. The instrument cluster also coordinates the display illumination for the radio (IRC), the cellular telephone (PHN), and the climate control Panel (CCP) anytime the ignition switch is in the RUN position.
Incandescent Dimming 1 (INC DIM 1)
The INC DIM 1 consists of lamps powered by CKT 8 (GRY). These are referred to as the park lamp backlighting because they are only active if the park lamps are on and the ambient light sensor indicates darkness.
Incandescent Dimming 2 (INC DIM 2)
The INC DIM 2 output is used as a general interior light source and an illuminated entry feature that provides interior lighting. The INC DIM 2 consists of lamps powered by CKT 1244 (BRN). When one or more of the following conditions occur, the INC DIM 2 lamps will be active:
• The interior lamps switch is active.
• The park lamps are on and the ambient light sensor indicates darkness
• The ignition switch is in the RUN position and the ambient light sensor indicates darkness
• A Class 2 message is received from the body control module (PZM) indicating that the courtesy lamps are active.
Dimming
The instrument cluster controls all of the interior dimming functions. The instrument cluster receives an ambient light level input from the ambient light sensor and determines whether it is light or dark. If the ambient light sensor is inoperative, the instrument cluster will assume a condition of darkness. Dimming of the VF displays is only allowed when the ignition switch is in the RUN position, the park lamps are on, and the ambient light sensor indicates darkness. If all conditions for the VF dimming are met, the instrument cluster uses the input from the potentiometer in the headlamp switch to determine the level of dimming. The dimming level is sent to the radio (IRC), the cellular telephone (PHN), and the climate control panel (CCP) via a Class 2 message. These modules then adjust the dimming level of their VF display. The instrument cluster provides dimming control of the incandescent lighting through the INC DIM 1 and INC DIM 2 outputs. The instrument cluster provides dimming control of the electronic PRNDL LED through CKT 1382 (PPL/WHT). The dimming level will very based on the potentiometer in the headlamp switch whenever the parklamps are on and the ambient light sensor indicates darkness, regardless of the position of the ignition switch.


1998 Cadillac DeVille ' DeVille, Eldorado (VIN E/K) Service Manual ' Body and Accessories ' Lighting Systems ' Diagnostic Information and Procedures ' Document ID: 489166
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Interior Lights Dimming System Check
Step
Action
Normal Result(s)
Abnormal Result(s)*
1
Turn the ignition switch to the OFF position.
Place the interior lamps switch in the ON position.
All incandescent lighting on the INC DIM D2 output turns ON. INC DIM 2 includes all of the lighting on CKT 1244 (BRN), which is the backlighting for the headlamp switch and the floodlighting for the vehicle doors.
Incandescent Lamps Inoperative
2
Place the interior lamps switch in the OFF position.
Turn the ignition switch to the RUN position.
INC DIM 2 lighting turns OFF.
All of the VF displays light. VF displays include the following components (if equipped):
• The radio (IRC)
• The cellular telephone (PHN)
• The driver information center (DIC)
• The instrument cluster (IPC)
• The climate control panel (CCP)
• Vacuum Fluorescent Displays Inoperative - All
• Incandescent Lamps Always On
3
Cover the ambient light sensor with the twilight OFF.
Place the headlamp switch in the PARK position.
The park lamps turn ON.
All of the VF displays dim in order to match the current dimming control level. All of the incandescent lighting for INC DIM 1 and INC DIM 2 light at the current dimming control level. INC DIM 1 includes all of the park lamp backlighting on CKT 8 (GRY) which is composed of the following components:
• The radio (IRC)
• The front cigar lighter
• The steering wheel controls
• The driver information center (DIC)
• The climate control panel (CCP)
• The instrument cluster (IPC)
• The heated seat switches
• The auxiliary blower switches
• The ash tray lamps
• The PRNDL lamp
Exterior Lights System Check
4
Rotate the headlamp switch dimming control in both directions.
All of the VF displays and all of the incandescent lighting dim and brighten in response to the headlamp switch dimming control.
Vacuum Fluorescent Displays Do Not Dim with Instrument Panel Dimmer Switch
* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.

bim or DIM ? the dimmer switch ! Interior Lamps
The interior lamps consists of two groups, lamps that can not be dimmed and lamps that can be dimmed. This first group consists of lamps that may not be dimmed. This includes those lamps that may be manually turned on by placing the interior lamp switch to the DOME position, or by opening a door or a compartment:
• Door courtesy lamps
• Footwell courtesy lamps
• Instrument panel (I/P) compartment lamp
• Overhead console courtesy lamps
• Reading courtesy lamps
• Rear compartment courtesy lamp
• Roof rail courtesy lamps
• Sunshade vanity mirror lamps

Interior Lamps Dimming
This group of interior lighting includes lamps which may be dimmed. This group uses a combination of class 2 controlled illumination and incandescent lamps:
• Air temperature switch
• Cigar lighter lamp
• Door switches
• Driver information center (DIC) switch
• Headlamp switch
• Head-up display (HUD) switch
• Heated seat switches
• HVAC control assembly
• Instrument panel cluster (IPC)
• Memory function switch
• Radio
• Steering wheel controls
• Window switches
For the interior lighting to be dimmed the following conditions must be met:
• A low light level has been detected by the dash integration module (DIM)
• Headlamp switch is placed in to the PARK or HEAD position
• Ignition switch is placed in the ON position
Then all class 2 displays and all incandescent back lighting will be illuminated to the level set by the instrument panel (I/P) dimmer switch. When the I/P dimmer switch is moved from MIN to MAX, all class 2 displays and all incandescent back lighting respond from minimum intensity to maximum brightness.
The DIM supplies battery positive voltage to the coil side of the PRK LP relay in the rear fuse block.
When the I/P dimmer switch is moved from MIN to MAX, then the instrument panel module (IPM), W/CJ2, or climate control panel (CCP), W/C67, applies a message to the class 2 communication circuit to the DIM. The DIM then applies a ground to the park lamp relay control circuit. This energizes the PRK LAMP relay and allows battery positive voltage to be applied through the DIMR fuse to the DIM. The DIM then illuminates the following incandescent lamps through the incandescent dimming output circuit:
• Cigar lighter lamp
• DIC Switch
• Headlamp switch
• HUD switch
• HVAC control assembly
• IPC
• Radio
• Steering wheel controls
The DIM also applies a message to the following class 2 controlled illumination components:
• Drivers door module (DDM)
• HVAC control assembly
• IPC
• Radio
The DDM will then send a message through the simple bus interface (SBI) to the RH front door module (RFDM). The door modules will then illuminate the following components through the incandescent dimming output circuit:
• Air temperature switch
• Heated seat switches (W/KA1)
• Memory function switch (W/A45)
• Power door lock switches
• Power window switches
The ground for these components are provided from the DDM and RFDM.
The following components are grounded at G200:
• Headlamp switch
• HVAC control assembly
• IPC
• Radio
• Steering wheel controls
The following components are grounded at G201:
• Cigar lighter lamp
• DIC Switch
• HUD switch

Do you have a dimmer for interior lamps? Like a rheostat, a little wheel that you turn up or down to brighten or dim interior lamps. Usually the instrument cluster lamps brighten and dim the same way.
Can you brighten and dim the other interior lamps?

Is your clock part of radio assembly? There is usually a dimmer control for interior lamps, you rotate it to brighten or dim interior lamps--dome--instrument cluster--radio illumination. The same thing should work for the clock. If clock is part of radio assembly, I guess you can remove radio and dig into it, see if you find the wiring for clock illumination.

I think the battery is shot

Is it over 5 years old replace it
then test the alternator output

Doubt the alterntor is bad the battery
won't hold a charge that is why your
lights are so dim,too much resistance
in battery cells

Hi,
Inverter is inside the LCD Screen. Mostly at the bottom in the middle. To locate the Invertor, you have to take apart the LCD Screen by removing the LCD Frame, removing rubber pads & screws (depending upon the Model of notebook you have). Moreover, the cause of dim/ dark display could be the faulty lamp. So, I recommend that you check both the Inverter and Lamp.
Another likely cause is a bad connection of power from motherboard to the LCD. So first check the connectors/ wires for any damage before proceeding to replace Inverter of lamp.
For your convenience and idea about LCD Display, I have found a general link about CCFL replacement. Click here for detailed and graphical DIY instructions about LCD disassembly.
Make sure you take proper precaution while working inside LCD, as the inverter generates a very high voltage.

Hope it helps! Good Luck! Thanks for using Fixya!
CreativeTECH

This is caused by either a poor ground connection to the head lights or an overcharging condition taking place in the voltage regulator of the alternator, the spikes in output voltage causes the head lights to brighten up.

A few things are going on - one or more could be the cause - but in most cases, a slight reduction in lamp brightness is nothing to be worried about, especially if it brightens again.

If you're removing your foot from the gas to go to the brakes, the engine RPM is falling - reducing the amount power from the alternator to supply the vehicle with electricity. Since your alternator puts out 13.8 volts and your battery supplies 12 volts, the vehicle power could be reduced by as much as 15%. Normally, the alternator output won't drop that low - but under certain conditions it might. One such common condition would be a loose V belt or serpentine belt. You'd probably hear it squeal when it was getting loose (have you checked it and your battery connections lately??). Switch on the fan to high speed and the air conditioning on - these devices draw a large amount of power to run, and while at idle or if a belt is slipping, the lights will probably dim a bit. You'll probably not notice anything if the engine RPM is in the 1500 and up range. All pretty normal expectations.

See if you can duplicate the situation on an empty stretch of road or parking lot. Watch the car's Voltage meter. If it dips when the lights do, it's probably a system wide voltage drop and if only barely noticeable - probably not worth worrying about. If the volt meter stays solid - but the lamps dim, it could be a loose connection - somewhere. This, is a much harder problem to find.

Since you're not losing engine power and you didn't say that the dim lights stay that way, you probably have little to worry about. Of course, having a mechanic check it out may give you peace of mind in exchange for a few bucks.

I hope this helps - good luck!

Check to make sure the hot conductor is feeding BOTH switches together, and
the switchlegs going to the individual loads

I answered this question many times. This is caused by a failed color wheel sensor. It faile gradually, first the lamp flickers, sometimes go dim for no good reason. Finally the lamp will not strike and you will get two red warning lights. I am factory trained and I stock the redesigned senor.