Vehicle: 2000 S80 Turbo 2.8l, 6 cylinder (B6284T), gasoline engine.
Symptoms: Cooling fan will not shut off, draining battery. Temperature gauge inside car seems to work normally; that is, it goes from low to the mid point seemingly normally as the car's engine temperature rises.
Summary: Immediately or soon after doing timing belt, thermostat, water pump, and crank/cam seals replacement, the cooling fan would not shut off. I've read enough posts here and elsewhere to ascertain that 99% of the time it's the control module built right into the cooling fan that has failed. In my case, however, there seems to be something more afoot and I am hoping for your help in diagnosing the problem:
What I've done:
- 1. Connected a new aftermarket (TYC 622140) fan to vehicle and that fan does stay off when plugged in. However, when car reaches operating temperature the fan will not turn on, nor does it turn on when A/C is turned on (if it makes a difference, I can't remember, however, if engine was cool or at temperature when testing with the A/C on). I supposed it is possible the new fan is faulty or not properly calibrated to this vehicle, especially since TYC informed me that they had had some issues (??) with earlier versions of this fan on S80's; however, my first instinct is rule that out, but without knowing what voltage the fan's controller is expecting at its signal wire, I do not want to manually test fan by applying 12v to its signal wire and risk damaging the transistors inside (I am waiting to hear from TYC about the type of signal this fan is expecting).
- NOTE: According to the wiring diagram from VIDA (attached PDF), there are no relays involved. The fan's control module uses transistors to turn the fan on/off, and the ECM controls the fan speed by sending either one of the two voltages listed in the specs listed below to the fan control module. Presumably, the arrangement of the transistors or some other logic (I'm not an electronics major!) in the module interprets the change of voltage to either restrict or not restrict the voltage being allowed to pass on to the fan's motor (???)
- 2. Voltage at the (purple) control wire at fan connector registers only 0.04v - 0.06v! (voltage increased to 0.06v only when I picked a different grounding point). I don't know if this due to the Pulse Width Modulation occurring (see below) and my volt meter getting confused, or if the ECM is not sending a proper voltage, or if there's a break in the wire between the ECM and the connector at the fan, a bad ground somewhere, the ECM needs to be rebooted or is bad, or something else.
- 3. Have not tested voltage at A:7 on ECM, but I did try to test what I believed to be the correct purple wire in the wire harness directly from the ECM towards the fan, but was unsuccessful in getting a reading.
- 4. Have checked to see if there are any ground cables that I may have left disconnected, but cannot find any that are.
- 1. Should I give the ECM more time to turn the (new) TYC fan on, or is that a lost cause considering the low voltage I am getting at the signal connector?
- 2. Should signal purple wire be registering a voltage greater than tested, or is it supposed to be only a ground?
- 3. According the VADIS/VIDA, and if I am understanding the chart below correctly, the ECM sends either 0.7v or 1.2v to the fan control module through the purple signal wire. Does that sound correct?
- 4. Can anyone be willing to check the voltage in their S80 at the signal wire (purple) to see what voltage their working ECM is sending to the fan when:
- - Engine is ON but cool
- - engine is ON but cool and A/C ON
- - engine ON and at operating temp with A/C OFF
- - engine ON and at operating temp with A/C ON
- 5. Being that I worked in the area of the coolant temperature sensor, could the sensor or its wire be faulty enough to confuse the ECM into thinking it does not need to turn the fan on, but not faulty enough to send a (correct/incorrect) signal to the temperature gauge in the dash?? That is, is the ECM more sensitive to the reading from the temp sensor than what the gauge displays, so that it thinks the engine is cooler than it actually is, and so it does not turn the fan on? The only caveat with this theory is that isn't the cooling fan supposed to turn on when the A/C comes on regardless of engine temperature??
- 6. Finally, do any of you who own a DICE tool know if it would give me the state of every single ECM input/output, including that of A:7, the output to the cooling fan control?
Specs according to VADIS on signal wire and wiring diagram:
