I finally got around to picking up a low-temp switch from an '87-89 4.9L fuel rail & wiring it into the low-speed relay ground. It works - just as the thermostat opens, the fans come on.
I still have to find a hi-temp switch to trigger hi-speed, and add some wiring to the dash so I can force the fans off, on hi (also with A/C), or leave them to run automatically. Eventually, it will be wired up similarly to this:
![heaterpipesensor.jpg I finally got around to picking up a low-temp switch from an '87-89 4.9L fuel rail & wiring it into the low-speed relay ground. It works - just as the thermostat opens, the fans come on.
I still have to find a hi-temp switch to trigger hi-speed, and add some wiring to the dash so I can force the fans off, on hi (also with A/C), or leave them to run automatically. Eventually, it will be wired up similarly to this:
[url=http://www.supermotors.net/vehicles/registry/media/575615][img]http://www.supermotors.net/getfile/575615/thumbnail/fancircuit.jpg[/img][/url]](http://www.supermotors.net/getfile/624973/fullsize/heaterpipesensor.jpg)
