Hi, all.
Just bought a 1993 Buick Century,
well maintained old car with 94,000 miles.

Dome light works with rear doors,
but not when front doors are open.
neither do the key in ignition alarm,
& headlight monitor alarm
Are there switches inside the door that are activated when door handles are pulled, or is there a module that is likely bad?
Also, possibly related-
The door lock button on passenger side works, but not on driver'* door.

Too bad there aren't simple switches like the ones on rear doors.
Thanks for any suggestions you have.
Regards. Terry

The dome light comes on when you open either rear door.....do the two front courtesy lights under the I/P panel also come on?


What happens when you rotate the dimmer switch all the way to the right, does the dome light come on and front and rear courtesy lights?

If yes, then you either have two bad front door switches(in the latch assembly), or you have a bad MALL module located in the courtesy center.....

From my personal experience, you will find it is the Multi Function Alarm Module plugged into the Convenience Center. In the Buick Century, it is is on the driver'* side of the dash, towards the lower part of the dash, closer to the driver'* door.
It is terribly difficult to get to the module, as it is mounted in the dash where it protrudes towards the driver.
The first time ours quit, all functions went completely dead. I finally got the thing unmounted, just unplugged and re-plugged the module. Worked for years until it did it again (completely dead), then it was easier as I zip tied it to the wiring harness where it was accessible. I'm a stickler about putting things back just like they were, but I draw the line at this non-sense. If the 2 occurrences weren't years apart (we bought the car new), I would probably open it up and look at the solder joints.

Thanks for the info.
A former GM mechanic I work with thinks i need to look at latch switches,
I'm leaning toward module.
I'll try to fish it out on my day off, and let you know what I learn.

For anyone searching this problem,I Found "Multi-Function Alarm Module" location help here- (Including info from Jerry CorvairGeek, thanks again.)

https://www.a-body.net/forums/showth...-location-help
And a new GM 22576829 Module here
Buy GM 22576829 Module, genuine OEM part

found this https://www.gmforum.com/performance-...estion-302894/
: GM Service Manual:
Interior Lighting System Description

Multifunction Alarm Module

The multifunction alarm module uses an inadvertent power control in order to supply power to the following lamps:

• The courtesy lamps
• The header lamps
• The reading lamps
• The instrument panel compartment lamps
• The luggage compartment lamps

The left front door jamb switch turns on the interior lamps through the multifunction alarm module. This is done by grounding circuit 394. When the left front door is opened, the switch closes. This action grounds and blocks the input to the module. The module then grounds the courtesy lamps and the header lamp in order to turn the courtesy lamps and the header lamp on. The following switches turn on the interior lamps by grounding the circuit 395 from the multifunction alarm module:

• The right front door jamb switch
• The rear door jamb switch

The panel dimmer switch provides a ground circuit for the interior lamps. This action turns on the interior lamps independent of the door switches.
The remote control door lock receiver grounds the interior lamps for approximately 40 seconds when one of the following conditions apply:

• A door unlock signal is received by the remote control door lock receiver module
• The ignition switch is turned to the RUN position.

The multifunction alarm module provides an interior lamps-on delay after the left front door has been opened. The lamps remain on until one of the following apply:

• 40 seconds has elapsed.
• The ignition switch is turned to the run position.
The 40 second lamps-on delay is sometimes reduced to 4 seconds. This reduction occurs if a front door is opened within 2 minutes after the ignition switch is moved out of one of the following positions:

• RUN
• START
• BULB TEST

The interior lamps will turn off immediately when the vehicle begins to move.
Voltage is applied to the multifunction alarm module at all times through the INT LAMP fuse. The multifunction alarm module applies voltage at all times to the alarm'* internal feature, the inadvertent power control. Voltage is applied to the multifunction alarm module through the ALARM fuse when the ignition is in one of the following positions:

• RUN
• BULB TEST
• START

Voltage is applied at all times to the cigar lighter through the CIG fuse.

Battery Run Down Protection

Inadvertent Power Control output of the multifunction alarm module applies voltage to the following lamps:

• The courtesy lamp
• The header lamp
• The reading lamp
• The instrument panel compartment lamp
• The luggage compartment lamp

If the ignition switch is in the OFF position for more than 20 minutes, the output timer will shut off power to all of the above lamps. If the vehicle traveled less than 24 km (15 mi) since battery voltage applied to the module, the output timer will shut off the lamps after 2 to 4 minutes.
You may reset the inadvertent power control output by one of the following methods:

• Open the left front door.
• Close the left front door.
• Turn the ignition switch to RUN.
• Turn OFF any interior lamps that were left on accidentally.

Power Output Diagnostic Mode

You may use a power output diagnostic mode in the multifunction alarm module in order to run a quick test on the operation of the following outputs:

• The courtesy lamps control
• The inadvertent power control

The power output diagnostic mode activates after you perform all of following actions:

• Close all of the doors.
• Set the park brake.
• Turn the ignition switch to RUN.

Before 15 seconds pass, perform the following steps:

• Open the right front door.
• Cycle the headlamp switch from OFF to PARK three times.

During a normal operation, the multifunction alarm module will flash the interior lamps until the ignition switch turns OFF. If there is an internal short in the multifunction alarm module, the module will chime in the following patterns:

• One chime every 3 seconds means that there is an inadvertent output failure.
• Two chimes every 3 seconds means that there is a courtesy output failure.

https://www.gmforum.com/trouble-shoo...est%2A-279872/

MALL Diagnostic Procedures..this covers 1996 to 1999 Bonneville
Problem:
Power door locks, interior lamps, and “Key-In-Ignition” and/or “Fasten Seat Belt” chime do not function or interior lights stay on all the time

Component Diagnosis:Body Control Module (BCM) AKA....Multifunction Alarm Lock Light (MALL,module)

First Steps:
1. Check door lock fuse (Fuse 1 - 20 amp) and chime fuse (Fuse 1D – 15 amp)
2. Check Courtesy Lamp/Power Mirror fuse (Fuse 6A – 15 amp)
3. Check for poor terminal contact at MALL and wiring harness connectors
4. Check for broken or partially broken wires.

Second Step: Perform the “MALL Module Internal Diagnostic Procedure/Bong Test"

The MALL module stores “history” codes if an electrical short occurs in the system during vehicle operation. The codes are “communicated audibly (a bong sound) by accessing the MALL module diagnostic mode. After providing any codes, the MALL module enters a functional test mode (called Input/Output or “I/O”) to assist in verifying that the inputs to the MALL are functioning properly.

1. To enter MALL module diagnostic mode/Bong Test:
a. Turn ignition switch to “ON”
b. Press AND hold the power door unlock switch while at the same time…
c. Cycling the headlamp switch six times, on and off, within 20 seconds of pressing and holding the power door unlock switch
d. Release power door unlock switch

Note: (To “Exit” the MALL module diagnostic mode, turn the ignition switch to “OFF”.)

The MALL will provide a number of audible “bong” sounds (and flash the “Fasten Seat Belt” indicator light with each bong) to identify the stored history codes for any malfunctions (short circuits) as follows:

# of “bongs” Circuit Short Condition
One: Fasten Seat Belt Circuit
Two: Battery Protection Circuit
Three: Courtesy Lamps Circuit

The MALL module will cycle through the stored history code(*) three times pausing for two seconds between each of the three cycles.

If no codes exist the MALL immediately enters the I/O mode. (Input/Output)

2. I/O Mode:

In the I/O mode, input from components in the system are “tested” by activating/deactivating each components input device and providing either one “bong”or NO, bongs (along with flashing the “Fasten Seat Belt” indicator light) to indicate whether a “short” is detected in the circuit as follows:

Component-------------------------------------------------Test
Auxiliary Chime --------------------------------------------Apply Parking Brake/Release, then Repeat
Interior Lamps-----------------------------------------------Turn on interior lamp switches, then turn off, then Repeat
Dome Lamp -------------------------------------------------Turn on dome lamps, then turn off, then Repeat
Door Latch Switches ------------------------------------ LH and RH Door latch switches, lift up handle only don't open,Repeat
Power Door Locks------------------------------------------Lock then Unlock, Repeat
Battery Protection------------------------------------------Turn on interior lamp switch, then turn off, then Repeat
“Lamps On” Chime ----------------------------------------Turn on headlight switch, then turn off, then Repeat
Fasten Seat Belts Chime and Indicator Light-----Latch, then unlatch driver’* Seatbelt, then repeat.
"Turn Signal On" Reminder Chime--------------------Activate turn signal, then turn off, then Repeat
Trunk Lid Ajar Light ----------------------------------------Activate/deactivate trunk lid latch switch, then repeat.

If you get a “bong” when testing a component, then the component is functioning properly.

If these components check out OK, then the MALL module itself needs to be tested for a short or the module may need to be replaced.
Last edited by Toddster; 03-10-2009 at 06:45 AM. Reason: clarification

If it were most any other GM, I would suspect the door pin switches too. The A-body doesn't have them in the door frame by 1992 at the latest, though the dimple is there where the hole would be drilled. They are inside the doors and activate as soon as the inside or outside door handles are pulled.

Those test functions don't apply to GM A-bodies and aren't in the shop manuals for the '92 or the '96. The A-body used what looks like any other '80s vintage seat belt chime module that added an auto locking provision. It controls the solenoids on the doors for the seat belt release (which should be disconnected at the solenoids, IMHO. They only increase the risk of ejection if the door opens in a severe collision. They are there to satisfy the legal mandate of an 'automatic seat belt') Theater dimming and an auto unlock function was added by '96. The anti battery rundown feature (if a light is left on) does not exist in any A-body through '96.

Another symptom of an inoperative module is a lack of a fasten seat belt light or chime. Failed door switches would not affect this function. You already mentioned the lack of a 'headlights on' chime, but this only occurs after the drivers door is detected open (though pulling the handle with the door locked and the lights on will activate the chime).

The A-body is an anomaly in the GM line after 1990. It was a very old car that kept selling and was high profit, even though it was allegedly to have been discontinued after the 1990 model.

I did the test described above, no flashing light, no chime. Going to look at door latch switches. Anyone have a handy link to door panel removal on these with door seatbelts? Thank you again!