Well, cooling is marginal with low speed fan when idleing with AC on high and air temp in the 90s. Since I have to plan on air temp in the 100s, the high speed would be a good idea so I've been working on it.
Adding high speed has some challenges:
1. The Taurus fan is not designed to have both high and low speeds powered at the same time. (Think that is OK with some 2-speed fans.)
2. Its also not designed to power on high speed unless the fan is turning at low speed. Switching on high speed when the fan is stopped draws excessive current and will burn out the motor.
3. There's a high momentary current draw with the fan enters high speed. High speed circuit needs fuse and relay for at least 60 amps.
So, I needed minumum 60 amp circuit breaker and 5-pin (SPDT) relay. It would have been best to find an auto reset circuit breaker but I didn't find one with sufficient capacity for the high speed and settled for a melting fuse. The low speed circuit is protected with a resetting circuit breaker so maybe that's good enough.
Neither could I find a 5-pin relay with sufficient capacity. Had to use two relays: one 40 amp 5-pin that just feeds power alternatively to the low speed controller or a 4-pin 60 amp realy for the high speed. Had a professional do the professional circuit design and professional circuit diagram.
While all these electrical gadgets were being installed I decided to prepare for a later improvement: headlight relays. Early Fords had a resetting circuit breaker for the headlights integrated in the light switch. These are known to go bad and leave you on a dark, 2-lane country road with no lights.
I KNOW that's true -- it happend to me. The car has a new FOMOCO light switch but a better solution is resetting circuit breakers and relays to avoid all that current thru the switch. That'll happen in the future, so why not at least get the circuit breakers added while the 2-speed fan is being set up?So, here is the assembly of the 60 amp hi speed fan fuse, two resetting 20 amp circuit breakers for the lights, and a 50 amp resetting circuit breaker for the low speed fan circuit. (Having separate breakers for bright and dim means I should always have one or the other.)
The steel bar is a buss for the four devices.
And, here it is with the two relays for the 2-speed fan circuits.
I didn't want all that uglyness visible in my engine compartment so its mounted behind the battery. Only the tops of the relays are visible.
There's good news and bad news. The operation was a success but the patient died. The circuits work just like the sensors tell them to but the sensors aren't giving good directions. The low speed controller has a probe in the radiator fins to sense temperature. It works fine by itself.
The high speed sensor is mounted in the thremostat housing on the radiator side of the 195* thermostat. Its supposed to switch the high speed on at 210* and off at 195* It switches on at about 210* but doesn't switch off till about 185*, which it never sees behind my 195* thermostat.
So, when the thermostat opens and dumps hot coolant into the radiator, the fan goes on low speed. But, when the heat builds to 210* and the high speed gets switched on, it won't switch off while the engine is running. Meanwhile, the probe in the aluminum radiator is cool and happy, not calling for the low speed.
When the engine is shut off, the high speed sensor in the thermostat housing is still hot so its running the fan on high.
I know this is way more detail than anyone cares about. Just had to write it down to help me think about where to go from here. For now, I just pulled the connector on the high speed sensor which makes it all work just like it did before all the gadgets were added.
I could reinstall my 180* thremostat and then maybe the sensor would turn off the high speed circuit. Hate to do that because the engine runs a LOT better up around 200*. Gotta think about it ...
Maybe if there was some heat on the intake manifold it would run well with a 180* thermostat. But, I also hate the thought of taking the intake off my newly assembled engine to check it out.
