Cooling fans won’t come on
96 Cutlass Supreme SL 3.1 auto (only 37K miles)
With the car in motion, the temp needle would point to about 1/3 of the way up, just above the “C” mark. But if idling in traffic or at a stoplight, the temp would creep upwards. The highest I let it get to was just below the “red” zone, right at the letter ”H”.
I checked and the radiator cooling fans never came on. If I got the car moving again the temp would come back down to where it should be. If I turned on the A/C then ONE of the radiator fans would come on briefly. This would cool the engine a little but not down to a point where I was comfortable with it. Also turning on the heat full blast would cool the engine somewhat but still not much. The only thing that would work every time to get the needle back down to 1/3 was to get the car moving again. I found a 3-wire switch/sender/sensor located near the thermostat, and if I unplugged that unit with the engine running, BOTH cooling fans will come on and the temp gage will go dead. Soon as I plug it back in, back to same problem.
So, on the advice of numerous threads on this forum, two A&P (aircraft) mechanics, and two parts stores, I replaced the coolant temp switch/sensor, the one located right by the T-stat. Did not fix problem. Cooling fans still will NOT come on when the engine starts to overheat. In fact, the condition is worse! Now, when I drive the car at any speed above a crawl, the temp gage will creep up to about ¾ of the way to the “H”. If I slow down, coast or idle for a while it will cool off to about 2/3 of the way to hot. If I turn on the A/C, the ONE cooling fan will run briefly but not enough to cool the engine very much. I can drive around town if I run the heat full blast and the mode switch on Defrost (which runs the compressor and so therefore will engage the ONE cooling fan briefly), and the needle will stay at 2/3 to ¾ of the way to hot. I live in a small town far from any shops so I’m afraid to drive out on the highway for fear the engine will overheat and do some serious damage. I took the cooling fan relays out and had them tested by AutoZone and the A&P mechanic. He said they are good. As a test I swapped them around, and swapped them each with the IGN relay which has same part number on it, no change. With the new coolant switch, I can still get BOTH fans to run by unplugging it, same as before. I have opened the bleed screw several times with the engine running and heat on, to make sure there is no air trapped in the cooling system but this has not helped at any time either. I can not find any fuses or circuit breakers that are blown or tripped. Put car back together and carefully drove to Autozone, because their answer was “there must be another sensor somewhere”. Three of their guys looked under hood and could not find “another sensor”. There is a switch or sensor located on the side of the radiator, but it is for coolant LEVEL, not temperature.
Various posts on this forum and others say the switch/sender/sensor I changed out is the only one that sends signal to the ECM to turn the cooling fans on. RockAuto has a listing for both a cooling temp “sender” and cooling temp “sensor” for this vehicle. Under the listing for “sensor” it shows the 3-wire unit that I have already replaced. Under “sender” it shows a choice of either the same 3-wire unit OR a 1-wire unit. Does not tell where that 1-wire unit is located. Autozone says there is no 1-wire cooling system sender or sensor applicable to this vehicle.
Please someone help me! The car is really nice but if it is not going to be reliable then I will have to sell it as-is or for scrap.