W126 Klima Relay

A week or so ago, I diagnosed that the likely cause of my non functional A/C in the 300SE was the W126 Klima relay.   The second generation W126 went to a Klima relay to control the A/C compressor.

The W126 Klima relay is more of a control unit than a simple relay.   It has multiple inputs that determine if the A/C compressor should not engage.   These include:

• During full throttle
• When the engine is very hot
• Invalid compressor speed (e.g slipping belt)
• Not enough coolant in the system

This additional functionality makes these relays more sensitive than the little silver ones used in the previous car.   I also had to change the same relay in my 560SEC.    It is important to note that the V8 relay is different to the one used in the Inline six.

The relay is located next to the fuel pump relay near the fuse box.  It is a simple swap out.

I bought a KAE relay.   I had previously replaced the relay with a rebuilt unit about two and a half years ago.   As it has already failed, I went with a new one.   The KAE unit is made in Germany so I hope it lasts longer than the rebuilt unit I went with.

With the new relay, the A/C is now cool again in the 300SE.    I may gut the innards of the broken relay so I have an easier way of jumping the ports for troubleshooting if/when I need to.