Coolant Temp Sensor/Fan Switch
20-03-2012, 07:31 PM
#1
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Coolant Temp Sensor/Fan Switch
Stupid question of the day...
(I've had a look through previous threads, but can't find an answer)
Why does the Engine need a Coolant Temp. Sensor AND a Fan Switch? I would've thought the two could be on the same circuit, the fan is switched on upon a high reading from the C.T.Sensor?
(I've had a look through previous threads, but can't find an answer)
Why does the Engine need a Coolant Temp. Sensor AND a Fan Switch? I would've thought the two could be on the same circuit, the fan is switched on upon a high reading from the C.T.Sensor?
20-03-2012, 08:25 PM
#2
Your on the right track, kind of....
Modern cars typically do just as you say, i.e. use the CTS as a reference point for all things temperature related, this also controls the temperature gauge, which conventionally would also require a dedicated sender.
However remember these cars are basic compared to nowadays, i.e. the engine management is just that, i.e. manages the engine.
This is not so in the case of a modern ECU/car, nowadays the ECU does alot more than just run the engine, one of the many outputs they control is the cooling fans, thus no designated fan switch is needed, also it's worth mentioning the way fans have improved with multiple speeds, compared to the Sierra's on/off single speed.
The Weber ECU'S are not capable of doing such a thing and so the radiator switch is used to complete the electrical circuit to the cooling fans (Which incidentally should be rewired, the bad standard setup is another story)
Alot of people who have fitted aftermarket management, do just as you predict and use the ECU to control fans, i.e. Autronic.
Martin
Modern cars typically do just as you say, i.e. use the CTS as a reference point for all things temperature related, this also controls the temperature gauge, which conventionally would also require a dedicated sender.
However remember these cars are basic compared to nowadays, i.e. the engine management is just that, i.e. manages the engine.
This is not so in the case of a modern ECU/car, nowadays the ECU does alot more than just run the engine, one of the many outputs they control is the cooling fans, thus no designated fan switch is needed, also it's worth mentioning the way fans have improved with multiple speeds, compared to the Sierra's on/off single speed.
The Weber ECU'S are not capable of doing such a thing and so the radiator switch is used to complete the electrical circuit to the cooling fans (Which incidentally should be rewired, the bad standard setup is another story)
Alot of people who have fitted aftermarket management, do just as you predict and use the ECU to control fans, i.e. Autronic.
Martin
20-03-2012, 08:43 PM
#3
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Thanks for the informative reply.
I think that's madness that a CTS/Fan Switch is needed to complete the circuit. More like "add more components to increase potential for failure".
I've just bought an alloy RS500 style radiator, so I thought I better get the 'uprated fan switch' from Motorsport developments.
While on their site I saw 'YB WEBER 4 SENSOR KIT WEBER. ACT-CTS-PHASE & CPS'...this is worth getting, yeah?
Do you still think I should do some rewiring?
I think that's madness that a CTS/Fan Switch is needed to complete the circuit. More like "add more components to increase potential for failure".
I've just bought an alloy RS500 style radiator, so I thought I better get the 'uprated fan switch' from Motorsport developments.
While on their site I saw 'YB WEBER 4 SENSOR KIT WEBER. ACT-CTS-PHASE & CPS'...this is worth getting, yeah?
Do you still think I should do some rewiring?
Last edited by Heathen; 20-03-2012 at 08:57 PM.
23-03-2012, 10:45 PM
#4
It isn't, the purpose of the radiator switch is solely to complete the fan circuit, the CTS is an input to the ECU to run the engine.
Yes you need the "Uprated switch" as the aftermarket rad is alloy they suffer from a heatsoak effect and so the fans stay on forever (If they diden't already that is on the standard radiator) this again with a terrible setup when new and incidentally the fans should have been rewired direct from the battery, the fuel pump can suffer problems and likewise need rewiring.
In my opinion the only sensor worth replacing is the CTS, as this is an important and crucial input and due to the type of sensor (Thermistor) they do go out of range after a while.
The CTS and Phase have gaps and provided this is set correctly I can't see why if it works it would need replacing personally.
The ACT is the same sensor as the CTS in a different housing (As it measures air temperature)
The CTS is the only sensor I have ever replaced, not that I had a problem, just for piece of mind, the one I removed was the original I suspect (Genuine Weber, where as the MSD one is aftermarket) I still kept hold of it.
Martin
Yes you need the "Uprated switch" as the aftermarket rad is alloy they suffer from a heatsoak effect and so the fans stay on forever (If they diden't already that is on the standard radiator) this again with a terrible setup when new and incidentally the fans should have been rewired direct from the battery, the fuel pump can suffer problems and likewise need rewiring.
In my opinion the only sensor worth replacing is the CTS, as this is an important and crucial input and due to the type of sensor (Thermistor) they do go out of range after a while.
The CTS and Phase have gaps and provided this is set correctly I can't see why if it works it would need replacing personally.
The ACT is the same sensor as the CTS in a different housing (As it measures air temperature)
The CTS is the only sensor I have ever replaced, not that I had a problem, just for piece of mind, the one I removed was the original I suspect (Genuine Weber, where as the MSD one is aftermarket) I still kept hold of it.
Martin
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