Experiencing a no-start issue with your 2002 Mercedes Benz Clk 320 can be frustrating. You turn the key, the instrument cluster lights up as normal, but nothing happens – no cranking, no engine start. This common problem can sometimes seem like a major fault, but often, the solution is surprisingly simple and affordable. If you’re facing this issue with your CLK 320, especially after noticing it becoming more frequent, the culprit might be related to your car’s relays.
Many Mercedes-Benz owners, especially those with models from the early 2000s like the CLK 320, have encountered intermittent electrical problems. One frequent cause lies within the relays, small but crucial electrical switches that control various functions in your car. Over time, the contacts inside these relays can corrode or develop poor connections, leading to issues like a no-start condition.
A hands-on owner of a 2005 CLK 320, with considerable mileage, experienced this exact problem. Initially, the no-start issue occurred sporadically, about once a week, but gradually escalated to twice a day. Drawing on experience with a previous Mercedes-Benz SLK 230 and an understanding of electronics, this owner decided to investigate the relays.
The approach was to disassemble and inspect the control relays. Upon inspection, it was discovered that several relays had poor internal contacts. For some of these relays, a gentle cleaning of the contacts with fine sandpaper was enough to restore full functionality. After this simple maintenance, the intermittent starting problem disappeared completely.
Based on this experience and further research within online Mercedes-Benz forums, a similar procedure was applied to the CLK 320. The focus shifted to the relay module located in the driver’s side hood (likely the Signal Acquisition Module, or SAM unit). Eight relays were disassembled and inspected.
The starter relay, labeled “S”, was examined first. While its contacts appeared to be in good condition, the possibility of intermittent malfunction couldn’t be ruled out. However, another relay, labeled “R” (identified as the terminal 87 relay, engine), showed clear signs of a bad contact. This “R” relay is crucial for engine electrical functions. The internal contacts of the “R” relay were cleaned using fine sandpaper.
In addition to relay maintenance, the owner also addressed the key and key receiver system. The infrared lens on the key and the key receiver in the car were cleaned. The key was disassembled for internal cleaning, and the two key batteries were replaced. These steps, combined with the relay maintenance, successfully resolved the no-start issue, and the problem has not returned for weeks.
To ensure long-term reliability, new relays were ordered from Mercedes-Benz to replace the critical “R” and “S” relays. The part numbers for these relays are:
- A 002 542 26 19 (Relay “R”, terminal 87, engine)
- A 002 542 92 19 (Relay “S”, starter relay)
The total cost for these genuine Mercedes-Benz relays was around $70, a fraction of what a dealer might charge for diagnosing and fixing a no-start issue, which could potentially involve replacing much more expensive components unnecessarily. This experience highlights that starting with simple checks, like relay inspection and maintenance, can save significant time and money when troubleshooting a no-start problem on a 2002 Mercedes Benz CLK 320. It’s a reminder that sometimes, the solution to complex car problems lies in addressing the basics first.
