Radiator fan oddity
05-21-04, 03:00 PM
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Radiator fan oddity
Ghost in the machine? Radiator fan will turn on after engine shut off - BUT ONLY WITH KEY IN IGNITION (ACC ON). This strikes me as wrong. Also, if it won't come on after a bit, I turn on the parking lights, bingo, it comes on - again, only with key in ignition.
Now why would I want to leave the key in the ignition while the fans cool the radiator ---and someone steals the car??? The TSB I read for this car says the fan should come on after the engine is off but I can't find anything about the key in the ignition or not. Natch, the dealer in Missoula was smarmy and not terribly helpful.
Here's how I think it's supposed to work: Idle the car for a minute to let the turbos spin down and cool. Shut off the engine, take out the key, lock the car...a few seconds later the radiator fans come on and cool the radiator for 10 minutes. Right?
Now why would I want to leave the key in the ignition while the fans cool the radiator ---and someone steals the car??? The TSB I read for this car says the fan should come on after the engine is off but I can't find anything about the key in the ignition or not. Natch, the dealer in Missoula was smarmy and not terribly helpful.
Here's how I think it's supposed to work: Idle the car for a minute to let the turbos spin down and cool. Shut off the engine, take out the key, lock the car...a few seconds later the radiator fans come on and cool the radiator for 10 minutes. Right?
05-21-04, 03:06 PM
#2
Re: Radiator fan oddity
Here's how I think it's supposed to work: Idle the car for a minute to let the turbos spin down and cool. Shut off the engine, take out the key, lock the car...a few seconds later the radiator fans come on and cool the radiator for 10 minutes. Right? [/B][/QUOTE]
I believe you have to do the fan mod first in order for it to work that way..
As far as the fan's staying on after you shut the engine off while key is in the ignition "on" position its because your temp is still reading the temperature is still to high that the computer still needs to cool the car down, once you take the key off fan shuts off..
I believe you have to do the fan mod first in order for it to work that way..
As far as the fan's staying on after you shut the engine off while key is in the ignition "on" position its because your temp is still reading the temperature is still to high that the computer still needs to cool the car down, once you take the key off fan shuts off..
05-21-04, 03:19 PM
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ok, i have a few questions. a few times (i dont remember what i did) i was able to get the fans to stay on after i pulled the keys out.
but even if there is a way to do this, what is the point? you are not cooling down the motor at all because the water pump is not pumping that cooled water into the motor? so what the hell is the point of cooling just your radiator?
but even if there is a way to do this, what is the point? you are not cooling down the motor at all because the water pump is not pumping that cooled water into the motor? so what the hell is the point of cooling just your radiator?
05-21-04, 03:58 PM
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don't race, don't need to
The fan coming on with the key turned to acc (run really) is due to the ECU sensing that the water temp is at or over 221F. This is the temp that the ECU would run the fans were the car running. This is occuring due to heat soak. Your turbos are still sitting at 300-400F at shutoff, and the heat is soaking into the rest of the engine. The thermosensor is reading higher than the 221F that the ECU uses to turn on the fans to low temp. With the electrical loads, the E/L sensor is telling the ECU that there is in fact an electrical load. This causes the ECU to turn on the fans to low at 210F. So, if the fans come on only with a load, the heat soaked temp is below 221F, but higher than 210F. But the stock gauge hasn't moved one iota, right? It's designed not to. That's why you linearize it.
The "fan mod" (the easy one that taps into the recall fan controller) is actually activating a different circuit, namely the one controlled by the thermoswitch. This switch is activated at 226F, and will turn the fans onto medium if the ECU is ALREADY running the fans due to the earlier conditions. IF the only thing telling the system to run is the thermoswitch connection, THEN the fans will run on low.
IF the ECU senses that the temps have been over 226F (i.e. the thermoswitch is closed) for two minutes or longer before shut off, THEN the fans will run for 10 minutes after shut off. If you ground the connection for this (the simple fan mod described above) for two minutes before shutoff, you acheive the same thing. The actual fan control at this point is from the recall add-on box, I believe. This is why you aren't having the fans run after shut off, it's a different circuit (kinda).
It is debatable as to the efficacy of running the fans after shut off. No, the pump is not pumping. BUT, there MIGHT be convective flow in the cooling system. UNTIL the thermostat closes. Or MAYBE not. Air WILL move through the engine bay with the fans on, but most of it is deflected under the engine, and does not give swirling flow around the entire engine.
A more effective fan mod is to tap the relays directly, and control them via a double throw switch. One position is low speed (grounds fan relays 2 & 4), the other grounds 2, 4 and 3 (I think, may be 1) to give medium speed IF the key is in the run position, low otherwise. It's called the "dysney mod", I believe.
Hope this helps!
The "fan mod" (the easy one that taps into the recall fan controller) is actually activating a different circuit, namely the one controlled by the thermoswitch. This switch is activated at 226F, and will turn the fans onto medium if the ECU is ALREADY running the fans due to the earlier conditions. IF the only thing telling the system to run is the thermoswitch connection, THEN the fans will run on low.
IF the ECU senses that the temps have been over 226F (i.e. the thermoswitch is closed) for two minutes or longer before shut off, THEN the fans will run for 10 minutes after shut off. If you ground the connection for this (the simple fan mod described above) for two minutes before shutoff, you acheive the same thing. The actual fan control at this point is from the recall add-on box, I believe. This is why you aren't having the fans run after shut off, it's a different circuit (kinda).
It is debatable as to the efficacy of running the fans after shut off. No, the pump is not pumping. BUT, there MIGHT be convective flow in the cooling system. UNTIL the thermostat closes. Or MAYBE not. Air WILL move through the engine bay with the fans on, but most of it is deflected under the engine, and does not give swirling flow around the entire engine.
A more effective fan mod is to tap the relays directly, and control them via a double throw switch. One position is low speed (grounds fan relays 2 & 4), the other grounds 2, 4 and 3 (I think, may be 1) to give medium speed IF the key is in the run position, low otherwise. It's called the "dysney mod", I believe.
Hope this helps!
05-24-04, 02:43 PM
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Great, thanks! Most modern cars run their radiator fans after engine shutoff and key exodus so there must be a point (Convection?). Currently snowing here in Montana - that outta cool it quick! Ha - like I drive it in snow - not!