Solving Heated Car Seat Problems
Heated car seats are a popular option for vehicles operating in colder climates. Manufacturers are able to incorporate heating grids into the seat cushions providing sales personnel with an additional selling feature. Here we’ll discuss how the systems work, how to diagnose problems and uncover model-specific issues.
Heated Seat Operation
In the past, this option was only found on high line luxury cars. Now carmakers are including heated seats on even mid-level models because the technology is inexpensive and appealing to potential buyers. The main component of the system is like a rear window defroster grid that heats the rear glass to melt ice and snow. The flexible heating elements are installed in the seatback or the seat bottom and often found in both locations. The passengers apply voltage to the grid through switches, relays and a timer circuit. Activating the switch closes the relay, sending power through the timer circuit to the heating element or grid. When the factory deploys adjustable switches, they regulate the amount of power sent to the grid by either cycling the timer or by stepping down the voltage via a resistor.
Importance of the Timer Module
The heated seat timer is often incorporated into a control module. Just like the rear defroster that’s cycled off every fifteen or twenty minutes to prevent overheating of the back glass, the damage could occur to the seat heating grid if left on for long periods of time. Therefore, drivers may notice the seat turns off after a fixed point of elapsed time. This is a normal condition. The original idea behind the convenience of a heated seat was to bridge the gap between cold operation when the automobile is first started, to when it reaches standard operating temperature.
After the vehicle is warmed up the heater should be ready to take over the task of providing passenger comfort. For this reason, people don’t often realize the seat warmer has even turned off. When the grid is disconnected by the timer module the switch mounted LED indicator light will remain illuminated on some models.
Symptoms of Heated Seat Problems
Many automobiles equipped with heated seats also have a remote start warm-up option. These vehicles can run for several minutes in the driveway making the driver’s entry a warm fuzzy experience. When the system stops working and the owner plants himself on an ice-cold seat, they will likely seek a solution. Fortunately, these systems are relatively easy to diagnose.
Diagnosing Inoperative Seat Heaters
When professional mechanics diagnose electrical problems they start at the load and work their way back. In this case, the load is the seat heating grid. The connector is usually discreetly located in between the seat back and bottom. On some models, the grid will have a separate connector and on others, it’s integrated into a larger harness with other functions such as power seats. The goal is to locate the power and ground wires that lead to the heating element. If a good power and ground are found at the seat grid, yet it refuses to heat, the malfunction resides in the heating element. If there is no power at the grid it’s time to start working back towards the switch.
Testing for power and ground at the timer control module and the relay are two additional test points before back probing and testing voltage at the control switch. If no power is found throughout the circuit, it’s time to check the fuse panel. Most heated seats are not protected by a fuse, but with a circuit breaker that automatically resets. Although circuit breakers are reliable, it is a remote possibility one has failed.
Most Common Heated Seat Repairs
When it comes to malfunctions in a heated seat system it’s fairly common to have a malfunction with the seat heating grid itself. The reason for this is the flexible element is exposed to large amounts of movement and variable passenger weight. Although designed to handle these situations, individual grids can open up in the heating element network causing intermittent operation.
With that said, certain automobiles are more likely to have failures in different areas. As an example, it’s possible for a carmaker to get a bad supply of switches or relays. In this scenario, when the manufacturer is made aware of an increased failure rate, they issue a service bulletin to the dealership level technicians. This can save them diagnostic labor on warranty claims. Therefore, vehicle owners experiencing problems should make an attempt at locating documentation about known heated seat issues through factory notification.