1999 clk convertible. The headrest light on the dashboard blinks when the car starts, but nothing happens when the button is pushed. Also, the top won't go down.

I don't know how that car compares to mine but I think they are both W202. On mine the headrest button only releases (lowers) the headrests. They are raised manually.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

On this one, the button both raises and lowers the headrests.

If you can confirm that the pump runs when they wont go down its because of a bad o-ring in the control valve that's blown out and allowing pressure to bypass the actuators. The valve is on the driver's side behind the rear seat back. If removed it can be disassembled to access the o-ring.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff