UrbanGardener Posted September 18 Share Posted September 18 I have thoroughly researched the auxiliary fan problem on this topic, nevertheless I have been unable to discover the solution. I seek assistance from someone. This pertains to the auxiliary fan of my 1991 560SEC. My vehicle in Southern California does not overheat. The maximum temperature I saw ranged from 100 to 120°C, particularly when ascending a hill. In my previous W124 E320, the auxiliary fan would activate at high speed if I unplugged the blue coolant temperature pin with the ignition on or the engine running. I inserted a 1.1 ohm resistor, resulting in the fan activating at a reduced temperature. However, I attempted to do the same change on my current 560sec, however the fan does not activate when I removed the Blue Coolant Temperature sensor connection. The low-speed fan does not activate upon starting the air conditioning, which I assume is due to a low freon level (the AC compressor engages, and I see bubbles through the condenser glass, however the AC does not emit cold air) or a malfunctioning auxiliary fan resistor. I was unable to access the resistor since it is situated behind the brake booster. Do you have any recommendations for accessing or inspecting the resistor? When I bypass the high-pressure temperature switch of the AC condenser, the fan activates at maximum speed. Upon doing investigation, I successfully identified the auxiliary fan relay C (the blue relay in my vehicle, as seen in the attached picture), and when I connect pins 30 and 86, the fan activates at high speed (with the ignition off). The fan activates regardless of whether the coolant temperature sensor is attached or unplugged. Measured the coolant temperature resistance, which is around 1.3 ohms at elevated engine temperature; likely not indicative of a faulty coolant temperature sensor. Link to comment Share on other sites More sharing options...
UrbanGardener Posted September 18 Author Share Posted September 18 Question: Why does the auxiliary fan not activate when I detach the coolant temperature sensor connection? I can hear the relay clicking when I bypass the coolant temperature sensor connection. Observation: A FUSE is absent from the little fuse box next to the main fuse box. Should I insert a blue fuse there, or should it remain empty? Attached is the picture along with the circles. Thank you in advance. Link to comment Share on other sites More sharing options...
DronePilot Posted September 18 Share Posted September 18 120 is significantly overheated. These vehicles should maintain speeds between 80 and 105 in all situations, including inclines. Link to comment Share on other sites More sharing options...
UrbanGardener Posted September 18 Author Share Posted September 18 Thank you very much. The maximum temperature I have seen so far is midway between 100 and 120, which I believe is either 105°C or 110°C. Link to comment Share on other sites More sharing options...
CodingProdigy Posted September 18 Share Posted September 18 Ensure that your freon level is assessed. It seems to impact the supporters. For clarification, the fans do not activate with the air conditioning; they only operate when a certain pressure is attained inside the AC system. A new radiator may be necessary, which is a straightforward task. Nissens products has an excellent reputation within this community. The fan viscous clutch presents a greater challenge due to the market's saturation with inferior quality products. I mention this because, even in 40°C heat, my automobiles seldom exceed 85°C. The auxiliary fans are designated only for emergency situations. Link to comment Share on other sites More sharing options...
MysteryReader Posted September 18 Share Posted September 18 In addition to the valuable counsel provided by both Tusabes and Ian, I would like to note that the low-speed fan is activated by the A/C pressure switch S32 located on the receiver/drier. The air conditioning unit is not producing cold air, possibly owing to the low refrigerant levels you mentioned, in conjunction with the low-speed fan operation. Low speed will not function with insufficient refrigerant. One may evaluate the low-speed fan components by bridging the vehicle harness connections at X (S32/2). An ordinary automotive blade fuse will be enough. When the ignition is activated, the low-speed fan should function. Link to comment Share on other sites More sharing options...
MysteryReader Posted September 18 Share Posted September 18 Link to comment Share on other sites More sharing options...
MysteryReader Posted September 18 Share Posted September 18 Furthermore, if this were my SEC mine, I would substitute all the fuses with new copper/brass element fuses, since the existing aluminum/brass connection interface is prone to deterioration over time due to the different metals. Procure many of the 30A strip fuses as well. They deteriorate due to aging, as I have seen. Link to comment Share on other sites More sharing options...
MysteryReader Posted September 18 Share Posted September 18 Link to comment Share on other sites More sharing options...
UrbanGardener Posted September 18 Author Share Posted September 18 I appreciate your response. Upon bridging the S32 pressure connections, the low-speed fan activates. Does this indicate that the auxiliary fan resistor is functioning properly? Intending to purchase copper fuses. Link to comment Share on other sites More sharing options...
MysteryReader Posted September 18 Share Posted September 18 The picture depicts a 1087 560SEC fuse box, hence certain elements may vary between the two. This picture depicts my 2001 SEC, which varies somewhat from my 1987 model and your 1991 one. Link to comment Share on other sites More sharing options...
MysteryReader Posted September 18 Share Posted September 18 Link to comment Share on other sites More sharing options...
MysteryReader Posted September 18 Share Posted September 18 I don't think you're missing anything.. Its just those locations are not used in your particular model and trim.. Link to comment Share on other sites More sharing options...
UrbanGardener Posted September 18 Author Share Posted September 18 I have connected pins 30 and 87 on the relay, and the high-speed fan activates. Arrow in the image. I am also lacking a fuse or relay in the center, as shown in your photograph. I highlighted my picture. Uncertain about its purpose. Link to comment Share on other sites More sharing options...
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