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Old 04-07-2019, 11:50 AM
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Diseasel300 Diseasel300 is offline
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The fans should only be running when the AC pressure comes up high enough to trip the switch. That's why when you short the wires together, the fans come on. That means all the gear controlling the fans works but your refrigerant charge is low or the switch itself is faulty. Think about it....

If you have the 1987 engine in a 1992 car, you have the wrong sensor setup for the afterglow relay. The 1986/87 engines had no afterglow function and used a different relay. The 90s cars use an afterglow relay and have an additional sensor in the head to tell the relay how hot the water jacket is to adjust its glow time and afterglow time.

Ideally you should change out that grey combination sensor to the correct one for your car. The high aux fan speed (overheating engine) is controlled by the climate control unit, and supposedly the later sensors are thermistors, not bimetallic switches like the grey sensor is.

The bottom line still applies here: The aux fans aren't there to cool your engine. That's what the engine driven fan is for. Unless it's >100˚ outside with the A/C on and you're sitting in traffic, the Aux fans will be on low speed and are triggered by the A/C pressure/temperature.

Fix your fan clutch. Check your refrigerant charge. You should be above 200-225PSI on the high side for the fans to engage. If you're lower than that, they shouldn't be on. Before adding refrigerant consider the ambient conditions - if it's in the 70s like it's been lately and there's low load on the A/C system, it's normal for the fans not to run since the head pressure will be less.
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