beltfed,
Don't shoot the messenger!
You couldn't tell if one relay failed, unless of course it failed 'closed'.
The thermo sensor (?) merely switches the control voltage for the two parallel relays that turn the fan on and off. The husky 30 amp contacts of the two relays handle the fan motor.
MAD contends if you split the motor load between two relays, the contacts will last longer, but more importantly, the load on the crimped terminals of the plug in sockets is now shared by two devices, so they won't overheat and fail.
It isn't uncommon for the spring clips on fuse holders to create a high resistance connection, heat up and loose their grip, so maybe a bolted or soldered connection on a fusible link makes sense.
As I remarked in my opening statement, I'm just reporting what I read on the MAD Electrical site. It is a interesting site, well layed out and full of down to earth info. It sounds like "Mark" has been there, done that, so I won't cast dispersions quite yet. That's my two cents!
Stuart
