Step-by-step instructions on how to change the battery on Mercedes-Benz CLK W209 and C-Class W203.
- (C180, C200, C230, C240, C280, C320)
- 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 model year
- CLK320 Cabrio CLK Class 209.465 112.955 from 2004-2005
- CLK320 Coupe CLK Class 209.365 112.955 from 2003-2005
- CLK350 Convertible CLK Class 209.456 272.960 from 2006-2009
- CLK350 Coupe CLK Class 209.356 272.960 from 2006-2009
- CLK500 Cabrio CLK Class 209.475 113.968 from 2004-2006
- CLK500 Coupe CLK Class 209.375 113.968 from 2003-2006
- CLK55 AMG Cabrio CLK Class 209.476 113.987 from 2004-2006
- CLK55 AMG Coupe CLK Class 209.376 113.987 from 2003-2006
- CLK550 Convertible CLK Class 209.472 273.967 from 2007-2009
- CLK550 Coupe CLK Class 209.372 273.967 from 2007-2009
- CLK63 AMG CONV CLK Class 209.477 156.982 from 2007-2009
- CLK63 AMG COUPE CLK 209.377 156.983 from 2008-2008
In this guide, you will learn and become familiar with the process of replacing the battery on Mercedes CLK-Class and W203 C-Class. On both these models, the battery is installed in the same location and the procedure is also identical.
On average, this entire process should only take about an hour or less. Additionally, we would rank this task as easy even for beginners. The most difficult part is getting the battery bracket off due to limited space.
What you’ll need
- AGM-94 Battery
- Group Size H8
- Minimum Cold Cranking Amps760
- Flathead Screwdriver
- 3/8 Ratchet
- 3/8 Long Extension
- 3/8 Long 10mm Socket
- 3/8 Long 13mm Socket
- Flashlight or a Reliable Light Source
- Extendable Magnet
- Gather all of the necessary tools and make sure the new battery is fully charged.
- Park the vehicle on flat ground with a reliable light source and set the parking brakes.
- Turn the ignition to the off position. Remove the key from the ignition.
- Open the hood latch located below the steering wheel. Ensure the hood stays open. In some cases the hood struts get weak and the hood may close as you work in the engine bay. If the hood won't stay up, have a friend help keep the hood open.
- Using a flathead screwdriver, carefully pop open the three clips holding the battery cover in place.
- Remove the cover and put it off to the side.
- Loosen the negative battery terminal nut with a 10mm socket to unground the battery properly followed by moving the terminal.
- Loosen the positive battery terminal nut with a 10mm socket and move the terminal wire to the side.
- Using the 13mm socket, remove the two nuts that hold the battery in place (one on each side of the battery). Space is tight so a pickup magnet can really help in this step. Remove the mounting bracket and move all of the cables out of the way.
- Disconnect the vent hose on the lower bottom of the battery. If your car has an AGM battery, it will not have a vent hose.
- The battery can now be removed and lifted up by the two handles. Get someone to help you lift up the old battery.
- Insert the new battery carefully inside of the vehicle remembering that Negative is on the left and Positive is on the right.
- Reconnect the vent hose and make sure that the mounting bracket is lined up.
- Insert each 13mm nut back into the mounting points on each side and tighten them to specification.
- Use a terminal wire brush to clean the terminals when possible.
- Connect the positive cable back on to the positive battery terminal and tighten it with the 10mm nut.
- Repeat the same steps for the negative cable.
- Place the battery cover back on top of the battery and lock in the three tabs.
We do no recommend using a backup battery to keep the vehicle powered up while you replace the battery. While connecting a backup battery saves a few minutes, it introduces an unnecessary risk especially if there is an accidental short or not enough power to keep all vehicle systems powered up.
- 10 ft/lbs. for both terminals
- 25 ft/lbs. for each mounting bracket bolt
Tips & Tricks
- The Positive terminal is always on the right if looking at the car from the front.
- The Negative terminal is always on the left if looking at the car from the front.
- Always check the size, AMPs, and volts of the new battery compared to the old battery.
- After disconnecting the terminals, use a wire brush and clean off the battery terminals carefully to insure of no major corrosion.
- Do not leave the key in the ignition while you replace your Mercedes-Benz C CLK battery. This can cause problems to the EIS module and the vehicle may not start.
- One the vehicle starts ESP and ABS light may come on. This is due to the steering angle sensor needing calibration. To reset the steering angle sensor start the engine and turn the steering wheel all the way to the left and right a couple of times.
- Synchronize the sunroof and windows by pressing the button and keeping it pressed for an additional 5 seconds after the window/sunroof reach fully open and closed positions.