Fb 14 Cooling Fan

[chamilka]

In my FB14 (1994) car radiator cooling fan rotates its full speed immediately after starting even when the AC is "off".

Engine does not get heated, even after driving for 20 km engine is so cold.

Have anyone experience this problem before? Is it something wrong with thermostat and something?

[Sylvi]

chamilka,

Get a electrician to check your thermostat wiring, some times thermostat two lead wires can bridge to gather can cause this problem.

If you can do it your self,

(1) Remove the two wires and start the engine then if the fan is not working, then go to the thermostat.

(2)To check the thermostat two terminals with an testing bulb, when the engine is cold,

(3) use a small multimeter test there is continuity on the thermostat when the engine is cold,

if there is continuity on the terminals, then there is a fault on your thermostat.

Fan normally comes on from the thermostat when the engine temperature reaches the correct working temperature.

Sylvi Wijesinghe.

[novice]

Hi,

Please check whether the Fan Switch is functional. This might also be a reason.

[Sylvi]

novice,

I don't think there is a separate switch for the engine cooling fan as this is connected to the IGN switch relay or direct to IGN switch and its is controlled by the thermostat on the car engine temperature. Switch is the thermostat.

If I am wrong please correct me.

Sylvi wijesinghe.

[fonfe]

novice,

I don't think there is a separate switch for the engine cooling fan as this is connected to the IGN switch relay or direct to IGN switch and its is controlled by the thermostat on the car engine temperature. Switch is the thermostat.

If I am wrong please correct me.

Sylvi wijesinghe.

A thermostat is not an electronic item or a sensor. It is a type of valve that is wax filled. The wax stays hard and keeps the valve shut until engine coolant has warmed up to a set temperature. The wax then melts and allows the valve to open letting coolant out of the engine block and to the radiator. It is designed to make warm up time of an engine faster thus improve fuel economy.

The fan switching on and off is controlled by a fan switch. This is will turn on and off at set temperatures. It will do this by being wired straight up to the fan and it completes the circuit through the relay thus turning the fan on or on newer cars it completes the circuit and sends voltage to the engine ecu which in turn, will turn the fan off.

Which method an fb14 uses I do not know, but it will be one or the other and is very simple to see which one it is. If it’s a direct fan switch (no ecu control) the wires going to the switch will be rather thick to carry the high current. The plug can be removed and bridged as a form of testing the fan works using a suitable piece of wire.

If the fan is ecu controlled the wiring to the switch will be the same thickness as injector wiring, temp gauge sensor wiring etc.

[chamilka]

Yesterday I checked the problem again my self. But fortunately now it is working fine. When I start the vehicle fans do not work unless AC is On and even when AC is Off fans turn on when the temp meter shows more than half. So it is exactly normal now. Thing that I didn't mentioned in my question was that I got this vehicle a week back and it was not even started for more than 6 months before. So unfortunately I am unable to tell you what was the exact problem. But searching on this I found that there is a thermo switch for fans it is even mentioned in the service repaire manual which I downloaded. So I guess this thermostat and thermo switch can be confusing.

Anyway thank you all, for your great suggestions.

[Sylvi]

A thermostat is not an electronic item or a sensor. It is a type of valve that is wax filled. The wax stays hard and keeps the valve shut until engine coolant has warmed up to a set temperature. The wax then melts and allows the valve to open letting coolant out of the engine block and to the radiator. It is designed to make warm up time of an engine faster thus improve fuel economy.

The fan switching on and off is controlled by a fan switch. This is will turn on and off at set temperatures. It will do this by being wired straight up to the fan and it completes the circuit through the relay thus turning the fan on or on newer cars it completes the circuit and sends voltage to the engine ecu which in turn, will turn the fan off.

Which method an fb14 uses I do not know, but it will be one or the other and is very simple to see which one it is. If it’s a direct fan switch (no ecu control) the wires going to the switch will be rather thick to carry the high current. The plug can be removed and bridged as a form of testing the fan works using a suitable piece of wire.

If the fan is ecu controlled the wiring to the switch will be the same thickness as injector wiring, temp gauge sensor wiring etc.

'fonfe',

First of all thank you for your detail post about, Thermostat Water temperature valve and fan control switch.

Yes You are Correct on your post about water temperature thermostat valve. That controls the engine temperature by the water and opening at correct temperature.

The fan control switch also does the same job to keep the engine temperature in best condition work according to adjusted settings.

What I meant was even the fan control switch operates at correct temperature. It is also a thermostatic switch.

Because all most all motors have cutoff thermostat bimetallic strip to cut off if the temperature goes up on the motor.

This fan control switch also works on the same principle which is fitted under the radiator.

Sylvi Wijesinghe.

[thush123]

my car is nisan march cooloing fan working directly so i want to know how much the thermostat

and where is the best place to do this

[The Don]

my car is nisan march cooloing fan working directly so i want to know how much the thermostat

and where is the best place to do this

Do you mean to say the Thermostat has been removed or disconnected from the circuit?

[The Don]

'fonfe',

First of all thank you for your detail post about, Thermostat Water temperature valve and fan control switch.

Yes You are Correct on your post about water temperature thermostat valve. That controls the engine temperature by the water and opening at correct temperature.

The fan control switch also does the same job to keep the engine temperature in best condition work according to adjusted settings.

What I meant was even the fan control switch operates at correct temperature. It is also a thermostatic switch.

Because all most all motors have cutoff thermostat bimetallic strip to cut off if the temperature goes up on the motor.

This fan control switch also works on the same principle which is fitted under the radiator.

Sylvi Wijesinghe.

Sylvi, I'm not entirely sure what you are alluding to with regards to the fan operation circuit and I'm not sure if I agree with fonfe either. Now my experience is with 90s and late 80s cars and this is how the fan circuit operates in those and the ECU is not involved in the process. It's possible that in newer cars the radiator fan operation is controlled by the ECU.

You basically have 3 components, the thermostatic switch, a relay and the fan. The circuit has a fail safe. If the link from the thermostatic switch to the relay is interrupted the relay will activate to the on position and start the fan. So the connection from the thermostatic switch (most of the time connected to the engine block along the return hot water line to the radiator from the engine) keeps holds the relay in the off position. At the pre set temperature, the thermostatic switch will activate the relay which will activate the fan, and when the temperature drops, the thermostatic switch will break the circuit de activating the relay and the fan will stop.

[Sylvi]

Sylvi, I'm not entirely sure what you are alluding to with regards to the fan operation circuit and I'm not sure if I agree with fonfe either. Now my experience is with 90s and late 80s cars and this is how the fan circuit operates in those and the ECU is not involved in the process. It's possible that in newer cars the radiator fan operation is controlled by the ECU.

You basically have 3 components, the thermostatic switch, a relay and the fan. The circuit has a fail safe. If the link from the thermostatic switch to the relay is interrupted the relay will activate to the on position and start the fan. So the connection from the thermostatic switch (most of the time connected to the engine block along the return hot water line to the radiator from the engine) keeps holds the relay in the off position. At the pre set temperature, the thermostatic switch will activate the relay which will activate the fan, and when the temperature drops, the thermostatic switch will break the circuit de activating the relay and the fan will stop.

'The Don',

Your explanation of radiator fan operation in vehicles of that era, on 2nd para of your post is correct.

Now days as ECU is monitoring the engine temperature also, if I am not mistaken the fan relay is controlled by the ECU signal for set temperature.

Which is correct as for my knowledge.My ECU knowledge is limited.

Only after owning new ECU controlled vehicles I started reading and gained knowledge about ECU working systems

If my post is not correct please do correct me, as I am a old school man. Carburetor Era.

Sylvi Wijesinghe.