Good call on the Ballast Resistor, but it's not the only possibility.
The Cooling Fans also depend on both a high-speed and a Low-speed relay - each fan has one of each.
They are relays #s 19 (Lft. low), 20 (Lft. high), 21 (Rht. low), 22 (Rht. high).
Since you cannot test the Ballast Resistor, only replace it, it's best to 1st test the relays to make sure their not the problem. Switch them around (the same type Relay is used for both high and low-speed) and see if the problem doesn't reverse itself. If not, it's the resistor.
Threaded Mode
