How to replace heated seats switch bulb? - 1991 Volvo 240

1. Blown Fuse: A blown fuse can prevent power from reaching the heated seat system. Check the owner's manual for the location of the fuse for the heated seats and replace it if necessary.
2. Bad Relay: A bad relay may also prevent power from reaching the heated seat system. Check the relay for the heated seats and replace it if necessary.
3. Bad Heating Element: The heating element in the seat may have failed. If this is the case, you will need to have the seat cushion removed to replace the heating element.
4. Loose Connections: Check for loose connections in the wiring to the heated seat system. Make sure that all connections are tight and secure.
5. Control Switch Failure: The switch that turns on the heated seat may have failed. If the switch is not functioning properly, it will need to be replaced.
6. Bad Wiring: The wiring in the heated seat system may have become damaged or frayed over time. If this is the case, you will need to have the damaged wiring repaired or replaced.

Heated Seat System Operation
The driver and passenger heated seats have 2 heat zone operating modes with 3 heat level modes and will operate only while the engine is running. The heat zones are determined by which of the 2 heated seat buttons are pressed, while the heat level is determined by the number of times they are pressed. Pressing the seat cushion button 1 time will activate the seat back and cushion heater elements in the high mode. Each time the seat cushion button is pressed the seat back and cushion heat level is reduced from high to medium, low, and off. Pressing the heated seat back button 1 time will activate only the seat back heater element in the high mode. Each time the seat back button is pressed the seat back heat level is reduced from high to medium, low, and off. During heated seat operation the heat zone operating mode may be changed without affecting the current heat level mode.
The heated seat switches are momentary contact switches and are inputs to the driver and passenger door modules. Battery voltage is supplied to the switch assembly from the door module, and when a heated seat switch is pressed and released a brief switch signal voltage is supplied to the door module. Whenever the door module receives an active heated seat switch input, the next heated seat operating mode is determined by whatever the current mode may be. The seat heater elements are controlled by the driver seat module using inputs from the door modules through Class 2 serial data circuit messages. The driver seat module controls the voltage supply and the ground circuits to the seat heater elements. When a heated seat function is commanded active, the seat module will switch battery voltage to the heater element supply circuits, and ground is provided through low side drive control circuits. During heated seat operation both the seat back and cushion heater elements are supplied battery voltage. The seat module grounds the appropriate control circuits for back only or back and cushion heating modes, and opens or closes the active control circuits as necessary in order to maintain the desired seat temperature. The seat module relies on inputs from thermistors located in the driver and passenger seat backs to control heated seat temperatures. The thermistors are 2 wire sensors supplied with a 5-volt referenced signal circuit and a low reference circuit from the seat module. Resistance through the thermistors varies with temperature causing the heated seat sensor signal circuit voltage levels to decrease as the seat back temperatures rise. The seat modules allow heated seat operation only while the engine is running which is determined by a Class 2 serial data circuit message from the powertrain control module.

Heated Seat Components
The heated seat system consists of the following components:
• Driver and passenger heated seat switches
• Driver and passenger seat back heater elements
• Driver and passenger seat cushion heater elements
• Driver and passenger seat back temperature sensors
• Driver seat module
• Driver door module
• Passenger door module

Do you know what B - body DTC -diagnostic trouble code are ?
DTC B2425 Driver Seat Heater Circuit
DTC B2435 Driver Seat Back Heater Sensor Circuit
DTC B3941 Front Seat Heaters Circuit

Heated Seat Always On
Step
Action
Yes
No
Schematic Reference: Driver Seat Schematics and Passenger Seat Schematics
Connector End View Reference: Power Seat Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
Operate the heated seat system.
Does the system operate normally?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Install a scan tool.
Display the Heated Seat Status parameter in the driver seat module Input/Output data list.
Start the engine.
Does the scan tool display the Heated Seat Status parameter as Off?
Go to Step 6
Go to Step 4
4
Display the Heated Seat Mode parameter in the door module Inputs data list.
Does the scan tool display the Heated Seat Mode parameter as OFF?
Go to Step 6
Go to Step 5
5
Turn OFF the ignition.
Disconnect the heated seat switch connector to the door module.
Start the engine.
Does the scan tool display the Heated Seat Mode parameter as OFF?
Go to Step 7
Go to Step 8
6
Replace the driver seat module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Is the repair complete?
Go to Step 9
--
7
Replace the heated seat switch. Refer to Front Seat Heater Switch Replacement .
Is the repair complete?
Go to Step 9
--
8
Replace the door module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Is the repair complete?
Go to Step 9
--
9
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 3


your best bet , have a qualified repair shop diagnose the problem

Carefully prise out the plastic gear lever surround and unscrew the 2 screws which are exposed at the bottom of the centre console. Then carefully prise out the console fascia - this will remove the radio surround (perhaps easier to remove the stereo first) and also the cigarette lighter / light level adjuster / heated seat switch cluster. Now it's just a case of unclipping the plugs and pushing the switch unit through from the back.

After removing the switch unit, you'll see 4 plastic bulb holders on the underside - 2 for the switch backlights and 2 for the 'on' lights. These turn 1/4 and can be removed.

Apparently these bulbs are pretty expensive to buy from Mazda, and I have been unable to get a part number to source them elsewhere, but they certainly can be replaced.

Possibly.... the only way I know to diagnosis this issue is with an amp meter in the circuit that heats the seats. Compare LH & RH seat heating current draw. If you find the pass seat is NOT drawing the same amount of current, further troublshooting is required. There are TWO heating elements installed in the seats -- seat bottom & seat back, and they are connected in 'SERIES'... so if either element goes/is 'OPEN', then it's component replacement time. There is a thermostat in the heating elements -- it regulates the seat temperature. One must isolate the two elements & check each one individually (seat bottom - checking resistance... and seat back - checking resistance). whichever one (or possibly both) are 'OPEN'. If you find resistance is normal (3 to 5 ohms), then the problem/cause may be in the switch (or its contacts). Using a test light (12 volt bulb), check for power (battery voltage) at the heating element connector to ground (chassis). If the bulb lights up, you know you have power at the switch and is sending it to the heating elements.

There is no way to just replace the bulb. You need to replace the hole switch. The bulbs are molded in the switch when they make them. To get the switch you need to go to dealer for it.

I have changed the lamps in a couple of the lock/unlock switch in the doors, the rocker does not come off without breaking,that said on some makes (Honda use more than one) you can unclip the back of the switch and there are 3 liliput bulbs soldered on the small circuit board, somewhere like Radio Shack sell them.

bulb within switch the switch is burned out.
although they are supposed to have a long life, it could be a defect. Check with Mazda or your owners manual for how to replace.

Had the same problem. Bought a new switch online for about $20. Remove the trim piece around the shift knob and then you can easily disconnect the switch and replace it. To remove the trim piece, start from the top and work your way towards the back of the car. There are three clips that hold it in place on each side and it will just pop off easily.

Steering wheel lights do not have bulbs you can change. The switch is a sealed asembly with an integral light. Each one costs around $110 at the dealership.

Heated seats have wires inside a fabric cover located betwwen the outside seat skin and the inner foam. Over time, they burn out. You can buy replacements from the dealer and have either them or an upholstery shop install them.

bad electrical grounds ... check all systems for poor grounds ..first poster... you have water or moisture issues as well as perhaps ground wiring issues causing premature faliures of bulbs and other.. the lens' pop off to replace bulbs