2015-2020 Kia K900 Master Window Switch: Failures, Part Numbers & Replacement

Symptoms of a Failing Master Switch

When the master switch begins to fail, it can cause a variety of frustrating electrical issues. Because the switch controls multiple functions, you may notice problems with the windows, locks, or mirrors, either individually or all at once.

• One or More Windows Won't Operate: The most common symptom is when a window stops responding to the switch. Often, a window will go down but refuse to go back up because the internal contacts for the 'up' command have worn out.
• Intermittent Operation: You might have to press a button multiple times or jiggle it to get a response. This points to worn or corroded internal contacts that are making an inconsistent connection.
• Only the Driver's Window Works: If you can only operate the driver's window, but none of the passenger windows respond to the master switch, it's a strong sign the master switch itself is faulty.
• Door Locks Behave Erratically: The power door lock button may stop working entirely, or only work intermittently. In some cases, a failure in the switch can prevent the car from recognizing that all doors are closed and locked.
• Power Mirrors Cannot Be Adjusted: Since the mirror control is integrated, a failing switch can leave you unable to adjust one or both side mirrors.
• No Response from Any Button: If the entire switch panel is dead, the first step is to check the fuse for the power window circuit. If the fuse is good, the switch assembly itself has likely failed internally.

Known Issues, Recalls, and Part Variations

The Kia K900 was produced in two distinct generations within this period, and the master switch is different for each. It is critical to buy the correct switch for your specific year and trim level.

Generation & Part Number Differences

• 1st Generation (2015-2018): These models use a master switch that is specific to the first-generation K900. An eBay listing suggests part number 93570-3T300 may be correct for 2015-2017 models, though this part number series is often associated with the Kia Optima. One Kia parts dealer lists 935703T300AHV for the 2015 K900. Extreme care must be taken to visually match your original switch and verify compatibility.
• 2nd Generation (2019-2020): These models use part number 93570-J6100-SA1. This switch is unique to the 2019-2020 K900 and is not interchangeable with the earlier generation or other Kia models.

Recalls and Technical Service Bulletins (TSBs)

While there are no recalls specifically for the master window switch, several recalls affect the K900's electrical and door systems:

• NHTSA Recall 23V-652: Affects 2015-2018 K900 models. The Hydraulic Electronic Control Unit (HECU) for the anti-lock brake system can short circuit, creating a fire risk while parked or driving. Owners are advised to park outdoors until the repair is completed.
• NHTSA Recall 16V-210: Affects 2015-2016 K900s with LED headlights. Electrical resistance can build up in the multi-function light switch (on the steering column), causing headlights to flicker or turn off. The fix is to replace the multi-function switch.

No specific TSBs for the master window switch were found, but some Kia models have had TSBs for door latch failures that prevent doors from opening from the outside.

Buying a Used 2015-2020 K900 Master Switch

Due to the high cost of a new OEM switch, a used unit is an excellent value. However, careful inspection is key to getting a good part.

1. Verify Your Part Number and Features

This is the most important step. The only way to be 100% certain of compatibility is to remove your existing switch and read the part number printed on it. While removing it, take photos of the electrical connectors to ensure the replacement matches exactly.

• Generation Match: Ensure the part is from the correct generation (2015-2018 or 2019-2020).
• Feature Match: The K900 was offered with options like power-folding mirrors and memory seats. The switch must have the correct buttons for the features your car is equipped with. A switch from a base model will not work correctly in a car with memory seats.

2. Physical Inspection Checklist

When you receive the used part, inspect it carefully before installation:

• Button Action: Press every button. They should move freely and have a distinct 'click' or tactile feel. Mushy or stuck buttons are a red flag.
• Connector Pins: Look inside the electrical connector ports. The pins should be straight, clean, and free of any green or white corrosion. Corrosion indicates moisture damage, which is a primary cause of failure.
• Casing Integrity: Check the plastic housing for cracks, deep scratches, or signs of being pried open.
• No Liquid Stains: Look for any chalky residue or dark stains, especially around the button seams. A spilled drink is a common way for these switches to get damaged.

3. Why Used OEM is a Smart Choice

For a low-volume, high-end vehicle like the K900, aftermarket support is virtually non-existent. Even if you could find an aftermarket switch, it would be risky. The master switch communicates with the BCM, and an aftermarket unit may not have the correct software or quality control, leading to unpredictable behavior. A used OEM switch guarantees perfect fitment, function, and electronic compatibility, as it was made by Kia for the K900.

Cost Comparison

The master switch for the K900 is an expensive part, making a used OEM unit a very attractive option.

Replacement Guide

Replacing the master window switch is a straightforward DIY job that requires minimal tools.

• Difficulty: 2/5 (Easy)
• Time: 0.5 hours
• Tools Needed: Plastic trim removal tool, Phillips head screwdriver.

Step-by-Step Instructions

1. Pry Up the Switch Panel: Using a plastic trim removal tool to avoid scratching the door panel, carefully insert the tool under the edge of the panel containing the switch. Gently pry upwards until the retaining clips release.
2. Disconnect Electrical Connectors: Lift the panel up. You will see one or more electrical connectors plugged into the bottom of the switch. Press the release tab on each connector and pull it straight out.
3. Remove Switch from Panel: Turn the panel over. There will be several Phillips head screws holding the switch assembly to the door panel trim. Remove these screws.
4. Install the New Switch: Place the new switch into the trim panel and secure it with the screws. Reconnect the electrical connectors—they are keyed and will only fit one way.
5. Test and Reinstall: Before snapping the panel back into the door, turn the car's ignition on and test every function: all windows (including auto up/down), locks, and mirrors. Once confirmed, align the panel's clips with the slots in the door and press down firmly until it snaps into place.

Frequently Asked Questions