Re: [DML] Schematic for fan/relay

[Martin Gutkowski <webmaster@xxxx>]

Hi All

I have had the opportunity to study the fan fail module as I had one in my car when I
bought it. The interesting things about it are as follows:

Although the fans are wired up seperately to the socket, they are connected together
inside the module. The primary reason for the fan fail module going wrong is the
pathetically small solder joints where the pins for each fan are connected to the board.
Combinations of flexing when plugging them in, and the heat generated by the small
connection results in these solder joints going "dry" - ie not proper electrical
connections, merely touching contacts.

I was however heartened to see that the original module did employ proper hall-effect
current sensing to light the fan fail light. It does not light the fan fail light if
something goes wrong with the main power relay supplying the fans.

As I mentioned a week or so ago, I have designed and am in the process of constructing a
DIY fan module for sequential fan engagement, and an additional system for detecting a
failure in the fans. The circuit is so elegangtly simple that anyone who knows how to use
a soldering iron should be able to build one. 75% of the problem with projects like this
is sourcing appropriate components! I have also incorporated "options" into the design
after some comments I received. Watch this space.

In other news, I have also designed a replacement for the lock module - again something
anyone with soldering experience should be able to construct. I will be testing all my
designs and instructions on a friend who knows how to solder, but not electronics as
such.

All the best

Martin
#1458