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 […]

W126 A/C no longer cooling

There is an old saying that deaths come in threes. I’ve not had any deaths in the family, but I had the A/C dead in three cars at the same time. The easiest was the A/C in my 450SLC that just needed a re-gas. The W126 A/C has been more problematic. Just as I got the system in my 560SEC mostly finished, the A/C stopped working on my 300SE.

I took the car in for the gas pressures to be checked and the gas was not below minimum spec. A tiny bit was added but my mechanic told me he […]

W126 A/C almost blowing cold

My fight with the W126 Air Conditioning system is almost over. When I purchased the car, the A/C worked rather well. After the water pump gave out, it looks like it shorted out the compressor clutch. Changing out the clutch is not much different to changing out the whole compressor, so I sourced a new compressor and receiver/drier. This was rather irritating as working air conditioning was factored into the price I paid for the car.

I went through the entire climate control system of the car as part of my troubleshooting. I found that the car had a missing […]

Further 300SE A/C Troubleshooting

Previously, I had identified that the cause of my A/C problems was the fuse blowing. I have been narrowing down the problem more and more to the compressor clutch. Therefore, I wanted to eliminate everything else as the compressor is every expensive and beyond my skillset. I had already unplugged two other components that are part of the fuse 5 wiring: The monovalve and the Aux water pump. The other component that is part of this circuit is the aspirator fan. This fan is a very small fan that draws air over the temperature sensor for the climate control. I […]

Troubleshooting W126 Climate Control

When I purchased my 300SE, the A/C worked well. I assume the overall Climate Control system did too. I never did test anything more than max A/C as the weather was very hot. Everything seemed fine, except for the little aspirator fan which was noisy. Unfortunately 3 weeks after purchase, the A/C stopped working. I was sitting at red traffic lights and adjusted the settings and it went warm. This indicated that it was probably not a leak in the system somewhere. Just to be sure, I had the system checked and it was not low on refrigerant.

The first […]