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I agree with the above post, your electric fan should turn on when you short the two leads together (the two leads that go the thermal switch mounted in the radiator).
However, the belt-driven engine clutch fan should be more than enough to cool the engine if you don't have the A/C on. I would suspect one or more of the following problems that would cause your car to overheat:
1. Radiator is cloged with dirt/debris. I would adivse flushing from the backside with a garden hose.
2. Front A/C condensor is clogged with dirt and debris. Remove front grill and use a dental pick or other fine implement to pick dirt/feathers/bugs out of the cooling fins and make shure the fins are straight. -A blockage on the AC condensor will limit airflow to the radiator mounted behind it. I also advise flushing it with water from the rear, but this is difficult since it has to pass through the radiator first and looses a lot of it's pressure (but still worth the attempt after you've picked out as much debris as possible).
3. Cooling system is low on fluid. You've probably already checked the fluid level, but it's worth checking again.
4. Coolant is improperly mixed or old. You should be running a 50/50 mixture of coolant and distilled water and changing it every 2 years. Use distilled water versus tap water since it doesn't contain extra minerals and chemicals (Chlorine, Iron, Calcium, Lime, etc). I personally use Volvo Coolant from my dealership since it contains no phophates and is much gentler on the aluminum components in the cooling system.
5. Radiator cooling passages clogged. A life of neglect, cheap coolant, and tap water will cause lots of sediment, calcium, and phosphate buildup that will choke the life from your radiator. This is not unlike how cholestoral clogs the arteries in a human. I've seen this on numerous occasions in various vehicles.
6. Missing fan shroud. If the plastic fan shroud is gone from around the engine clutch fan, the fan will not be providing adaquate suction on the back of the radiator to pull the air through (when at idle and not moving).
7. Engine splash pan (plastic belly pan) is missing. The presence of the plastic engine pan helps keep air flow coming from the front of the grille, through the radiator and into the engine bay (rather than being sucked up from the ground below due to fan turbulance, etc.
7. Mechanical engine clutch fan is failing.
9. Thermostat issues. I wouldn't suspect the thermostat based on your symptoms, but if you haven't changed it in the last 5 years, it would be worth doing so.
10. Water pump. -again, same as above, I wouldn't suspect this is the problem based on your symptoms, but I've seen weirder occurances that I though I had ruled out.
God bless and I hope you track down the problem.
Fitz Fitzgerald.
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'87 Blue 240 Wagon, 255k miles.
'88 Black 780, PRV-6, 148k miles. (B280 engine, the newer brother to your B28)
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