RWD - 1994 940t power seat curiosity

Volvo RWD 900 Forum

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1994 940t power seat curiosity 900 1994

Dear greenvolvo,

Hope you're well. I've never needed any other items besides a 12-volt source and two wires from that source, one to the red-wire and one to the black-wire terminals on the seat's wiring harness power connector. The seat power supply is a two-wire set-up.

I use a small 12-volt sealed lead-acid battery as a power source. I use alligator clips to secure the + wire to the red wire on the seat's wiring harness terminal, and to secure the - wire to the black wire on the seat's wiring harness terminal.

With power thus supplied, I can move the seat in all directions possible: front/back; raise/lower (height); tilt (seat cushion reltive to the floor pan; and angle (back relative to the seat cushion). If only some of the functions work, that likely is the result of a seat computer failure.

If the seat computer has failed, you can supply power to each of the motors (one-at-a-time). Tilt the seat, so that you can see the underside. You'll see a large connector at the seat computer, from which wires run to each of the seat's motors. I don't recall which wire pair feeds each motor. You can, by trial-and-error, ascertain which pair drives each of the three under-seat motors.

Once you have mapped the wires, supplying 12-volts to a motor will produce movement. Move the power source wires' alligator clips to each pair of motor wires.

If each motor runs with direct-supplied 12-volts, then a replacement seat computer is needed. The likely failure point is/are one or more of the relays on the seat computer's circuit board. These relays are "open frame", i.e., they are not in sealed capsules.

I'd be surprised to hear that a seat motor has failed. These motors get relatively little use, so even 25-year-old motors should have many years of service ahead.

Should you need a replacement seat computer, a salvage yard should be able to supply it, if you don't want to buy a brand-new unit. These computers were used in 940s and 960s.

Hope this helps.

Yours faithfully,



New 1994 940t power seat curiosity [900][1994]
posted by  greenvolvo  on Fri Jun 14 12:58 CST 2019 >

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