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Got The Cooling Fans Working But...

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The 91 Fleetwood was overheading, no warning light came on but I sure could hear something boiling under the hood. For those that don't remember the cooling fans stopped working about a year ago but we parked the car in lieu of the 95 LHS which is now totalled.

So I figured perhaps the cooling fans are not coming on because the Coolant Temp Sensor (CTS) is not telling them to come on, hense why I did not get a warning light come on when the engine was boiling itself. I unplugged the CTS and the fans turned on right away. I am not sure if they are always on or not but I know that they work. Is there a resistance test to do on the CTS to see if it is in spec, and if someone knows it could they post it :D . As always thanks in advance.

BTW 1991 Fleetwood FWD 4.9L


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Something strange is happening. I'm not sure for 91 Fleetwood, but I think the temperature sensor scheme should be same like I have in 94 STS. It has low resistance when temperature is high, and it has high resistance when temperature is low. Again, I'm not sure about 91, but 94 sensor has around 3K Ohm when temperature is 70F. When you unplugged the sensor, computer should think that temperature is freezing. You got opposite, which is really strange to me. 94 and later models have 3 relays, which allow connecting fans differently and having 4 statuses: both off, right on high, both on low, and both on high. If 91 Fleetwood has something like that, I can't explain what's happening, but one way: possible that after you unplugged sensor and computer thinks the temperature is getting lower it switching mode from both high to both low. In that case if some relay is bad we can have the situation, that mode "both fans on high" doesn't work, and mode "both fans on low" does. I assume that scheme of 91 in that part is the same as on 94. Give more info. What engine really hot when you unplugged the sensor? Other side, I don't know if its possible to unplug the sensor when engine is hot and do not burn hands.

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