Why do you want to get to it,what are you going to do with it when you do,you can't fix them and they VERY,VERY(nearly never) rarely need fixed anyway, has someone told you it's faulty?anyway it's under the dash behind the heater controls with pipes connected through the bulkhead to your radiator system,usually two pipes one above the other.It shouldn't need attention unless it is pouring out water inside the car,if it's air locked you sort it from the engine bay.
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