Blower motor relay / no "LOW" fan speed / Delanair Mk II AC XJ Series III

Dear all,

as some of you might have experienced, the Blower speed relay (part no. C46179, if I’m not mistaken) of the Delanair Mk II is not the most reliable part. Especially the “LOW” speed section of the relay seems to be prone to failure, as can be seen by searching the posts in the forum.

But here’s the good news: There is an easy workaround. As the original relay is basically an addition of four relays in a single box, it is possible to replace single failing relays within this box by adding cheap external relays. In case of the “LOW” speed relay, this is a 15 to 30 min. job. You don’t even need to split wires: Black (ground), Brown/Yellow (12V) and Yellow (switched by the relay from Ground to 12V), which are connected to the Blower speed relay, can be disconnected there (they just serve the “LOW” speed circuit, not needed for the other blower speeds), and then connected with the new relay (of the simple on/off type). Brown/Yellow (12V) can be used for both: switching the relay and the workload. That’s it. There is enough space behind the center console to store the new relay. For more information about the wiring and the location of the parts see the ROM or the Haynes’ manual.

I just though I should share my experience, as this seems to be a common issue, which is easily solved. Of course, don’t forget to document the installation for future repair. Additional parts always ask for explanations.