[SwedishBus]

Assuming that the seat is making no clicking noises, the switch panel is the likely area of failure in the V70 electric seat. It is fairly exposed to the weather when the door is open, but also incorporates some fragile (in old age) circuit-board electrics. As I will explain later in this thread, there is one specific area that is likely to fail in old age, which is very easy to repair with a soldering iron (small tip circa 1mm required), some solder, and a little time. You will also need a 12v test-lamp with its own built-in battery for continuity testing (a 12v battery, some wire, and a 12v/5W sidelamp bulb will make a good tester), or a simple electrical meter with a Resistance function will suffice.

The first job is to safely remove the switch panel from the side of the seat. There is no need to disconnect the main vehicle battery for this work, though caution is needed to ensure that all correct procedures around the airbag system are adhered-to. It will help with diagnosis and confirmation-of-repair if the seat module is otherwise left powered-up, which is its normal state with the ignition key in the "OFF" position, or even out of the column.

The main thing is to make the seat panel as easy to maneouvre as possible, so that means disconnection of the green multiway plug on the front of the seat module that feeds the harness going across to the switch panel. Volvo have chosen to make thsi plug as fiddly to remove as possible; the latch that needs to be depressed into the plug to release it from the module is facing down towards the module mounting panel. A small digit can just squeeze into the gap to push the latch whilst the plug is gentle wiggled free.

Release any tie-wraps securing the harness to the seat frame.

(see photo 1) Lift the front-facing edge of the switch panel straight upwards to release it from the airbag trigger housing, then knock it backwards towards the rear seat to disengage it from the seat tubular piece near the seat buckle. IT IS IMPERATIVE THAT THE SEAT SIDE AIRBAG TRIGGER IS NOT ACCIDENTALLY PUSHED TOWARDS THE SEAT CUSHION DURING THIS STAGE.

As soon as the switch panel and seat trim surround is loose from the seat, carefully remove the inhibitor (orange coloured) plastic piece from its stowage under the trim panel, and insert it between the inner and outer parts of the side airbag trigger unit. Do not knock or accidentally push the trigger face towards the seat. Once the inhibitor piece is in place, things are much safer to work-on.

The switch panel can be removed from the seat side trim panel on the workbench. There are three screws (Torx T20) securing the switch panel. The tie-wrap securing the harness to the seat trim near the airbag trigger clipping area will need to be cut to release the harness. It is important on reassembly to renew this tie-wrap, as it prevents the seat switch harness from fouling the airbag trigger unit.

(see photo2) Release the plastic latch at one end of the switch panel, and push the panel upwards (in its normal, fitted orientation in the car) out of the trim. It might be a bit tight on its dovetailing, but it will just slide out. Guide the harness through the trim, and then the module connector plug.

The switch panel can be further dismantled by removing 8x screws securing the circuit board to the switch front panel. Note that two (ringed) are also cord-grip screws. It is important that the switch buttons are facing down towards the workbench, and stay in that orientation during this work. There are four tiny springs (yellow-ringed in photo3) that will escape from the memory buttons if the panel is inverted, then there will be fun trying to find then, let alone feed them back into the buttons. Just work with the circuit board facing upwards towards you.

(see photo3) The main concern on this circuit board is the harness connection plug that is header'd onto the circuitry (red-ringed in photo); the joint is mechanically loaded, and the solder cracks. It is obvious from each of the microswitch units where the circuits go, and the best test is to operate the switches in turn and measure the continuity to the common 12v feed to them. This is the main circuit around the outside of the circuitboard, it is fed by the Orange and Blue wires in parallel to each other (either will work as a test-point). If the header solder joints have both failed on these two wires, then all switch functions will cease to work, hence this switch panel is a valid part of the overall seat diagnostics after a fusebox check for supply voltage. The wire colour that feeds the main seat module (pin_1 on plug A) is a Green with a Red tracer, and this should have 12v on it permanently when the car is "awake" with the doors open.

All the microswitches have a unique wire colour which should show good continuity to the Orange or Blue wires as each is pressed. Note that the switch contacts are made on each unit in the opposite direction to that which the switch is pushed. The functions and their wire colours are;

Forwards - Red wire
Backwards - Black wire
Rear raise - Yellow/white wire
Rear lower - Orange/white wire
Front raise - Brown/white wire
Front lower - Red/white wire
Backrest raise - Violet wire
Backrest lower - Green/white wire

(see photo4) It is likely that a close inspection of the header joint for the harness plug has broken (cracked or "dirty" looking solder) joints on one or more pins (see close-up photo). To rectify this, the joint should be heated with a fine-tip iron, wiped clean of old solder (an old cloth will suffice), the joint fluxed slightly, and new solder added back into the joint. The important thing is to work progressively through all the affected joints in turn, and avoid bridging across between the pins with solder that is being removed/added.

Reassembly, as they say, is the reverse of disassembly, but it is well worth doing a series of checks before putting everything back. Firstly, check for continuity between all adjacent pins - there should be none, except the diagnostic resistance pins with the Yellow and the Grey wires - that is normal. Secondly, assemble the switch button panel back to the circuit board, then plug it into the car and check that everything is now working - don't panic if it doesn't, as if the switches have been duff for a while, there is a chance the motor/s have seized in the meantime from lack of use. That is a further repair!

Remember to secure the harness lead inside the seat side trim over the airbag trigger moldings (that clip the trim down over the airbag trigger) with a new tie-wrap, and leave the harness plug loose whilst the switches/trim are refitted to the seat - it will lessen the chance of the airbag trigger being pushed accidentally once the orange piece has been removed and re-stowed. Locate the trim panel first over the tube at the rear edge of the seat, ensuring the seat buckle is clear of the area, then lower the front of the trim panel squarely over the side airbag trigger housing, and push downwards to latch.

If the seat motors need investigation, that is to be continued....

Apologies for lack of photos - forum is having difficulty uploading these right now. To be added later.