414 and 417 are the cabin temp sensors, located above the front window and behind the grab handles. There is a little plastic flap at the base of the handle that folds back to reveal a torx screw that holds the handle on.

Once the handle is off, pull out the rectangular plastic. Behind that is the sensor and fan! Don't take those out, but clean them. Either use a vacuum cleaner and suck out the dust bunnies, or use a wood toothpick and get the dust and dirt out.

Be careful in there, those things are fragile.

Without a temp sensor, the ECC doesn't know what to set the cooling/heat at. It doesn't fix your AC problem, but will let your ECC work again.

So, most folks have leaking AC evaporators (very expensive to fix), a bad pressostat (easy), or an accumlator bottle that is full of oil. You need to check the pressure of the system, with the AC on before you do anything rash. The psi readings of the cooling system should be around 40, at below 25 the system will not start the compressor.

Klaus
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Why are Volvos so endearing? Its just a car.