1998 Mercedes-Benz ML320 Seat Heater Replacement Cost

Heated seats are an option in some cars, trucks, and SUVs that allow the front seats to be warmed in cool climates. Occupants can switch on a heating element that warms the seat cushions. The seat heater is the element inside the seat that produces the heat.

When the seat heater switch is turned on, voltage is supplied to the heating element (the seat heater) which provides resistance against the electrical current and produces heat - similar to the way a toaster works. The wires of the seat heater are laced back and forth across the seat cushions underneath the seat cover in order to distribute the heat evenly across the surface of the seat. A sensor is used to measure and regulate the temperature of the seat heater. A control module may be employed to aid in temperature control. And some vehicles have a built-in timer to shut the heater off.

The most common problem with heated seats is a heater that will not turn on. When the switch is engaged, heat does not build up in the heating element. The wires that make up the seat heater are very thin and prone to wear and breakage over time. Because of this, the most common cause of a heated seat that does not work is a faulty seat heater element. But it can also be the result of a simpler problem: a faulty switch, a corroded electrical connection, or a blown fuse. Some drivers complain that the heater becomes too hot. In some cases, a malfunction in the seat heater can cause the heating element temperature to rise too high, causing burns to the occupant.

A seat heater that does not work at all is not a cause for concern. In most cases it simply will not work. If a short circuit is the cause, though, damage to sensitive components in the electrical system could result. A seat heater that is malfunctioning and does not regulate the temperature properly can get too hot and cause burns to the occupant. This condition should be checked and repaired as soon as possible.

Seat heaters installed at the factory are expected to last the lifetime of the vehicle. However, excessive wear on the seats can decrease the useful life of the delicate seat heater elements under the seat covers.

The most common cause of a heated seat that does not work is a faulty seat heater element. The seat heater is also the most difficult component in the system to replace, since the seat must be removed and disassembled in order to access the heating elements. A technician will start with simpler (though less common) causes of seat heater problems. It is possible that a fuse has blown. The electrical harness plug that connects to the heater could be corroded. A broken wire could cause an open circuit or a short circuit, so the technician will check that voltage is present at the connector. The on/off switch could be malfunctioning. The control module could be at fault. Most of the time it is the seat heater though. So, with these other problems ruled out, the technician will remove the seat and test the heating element. If the element presents an open circuit, the seat heater is bad. Some seats have multiple heating elements installed in series, which means that if one breaks, neither element will work.

If one or more of the seat heater elements is found to be broken, the technician will (with the seat out of the vehicle) disassemble the seat, remove the seat covers, and pull the matrix of wires that comprise the heating element from their adhesive bonds with the seat to remove the heater. The new seat heater is adhered in place, connected, and tested before the seat covers are reinstalled, the seats reassembled, and finally reinstalled in the vehicle.

RepairPal recommends that drivers pay particular attention to whether or not the seat heaters are switched "on." It may be difficult to gauge how hot the seats are getting until they are too hot. The auto industry is beginning to take notice of the concern and may one day make the control center for the seat heater more visible to occupants, but for now it is important to pay attention. See a repair professional if the seat heater is not working or if it gets too hot.

It should be noted that, when using a seat heater, it is important to pay attention to how hot the seat is getting. Some drivers complain that, even under normal circumstances, the seats get too hot. Some complain of injury and burns. Occupants with certain health concerns that lead to sensory deprivation or skin conditions, as well as young children, may be especially susceptible to injury associated with seat heaters.

Seat heater replacement should be left to a repair professional. Many delicate wires connect the seat to the vehicle and the heater to the seat. Many vehicles are also equipped with seat-mounted airbags and SRS seatbelt pretensioners attached to the seats. Care must be exercised when removing a seat with these features (not to mention disassembling the seat). It may also be necessary to reset the Supplemental Restraint System when the seat is installed. Most seats are held in place by only four nuts or bolts, but even the job of wrestling the seat out of the vehicle without causing damage is a difficult operation best left to a professional.