rad fan not working

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david brooks

New member
Joined
Jul 4, 2012
Messages
2
the rad fan does not strt when the temp gauge goes up when standing in traffic etc it does come on when i use the air con any ideas please someone said it may be the switch censor if it is where is it located and is it a diy job to fix thanks
 
Welcome aboard :thumbs:

you will find a lot of info in this thread however as far as I know Topmansparkie's problem remains unresolved

http://www.projectpuma.com/viewtopic.php?f=19&t=16897" onclick="window.open(this.href);return false;
 
Rad fan should always be running on slow speed when the A/C is on and fan switch in car is on.
Rad fan normally cuts in on high speed when water temp goes above around 105 degrees C.
 
sorry if ive confused the fan works when the air con is on but does not start when the temp guage in the dash goes up close to red when standing in traffic if it is the switch where do i locate it and is it a diy job thanks
 
Hiya,firstly you need to make your posts in the thread by typing under the previous comment then clicking on submit
down there.


What you did was start a new thread as if it was a new topic so no one can see that its associated with your last post.Its a bit like going into another room and carrying on the conversation you were having in the last room they wont know what your talking about :thumbs:

Please read the full thread in the link I gave as it would appear the same problem as yours and changing the sensor which was not cheap did not solve the problem.
 
quest63 said:
as far as I know Topmansparkie's problem remains unresolved
CORRECT! You're not losing the plot after all....

Keep the ideas coming people... I'm watching this one!
 
Mine hasn't worked in about 2 years lol... and the cooling is just fine.... but i try not to keep it idling too long. Traffic jams on the M25 never help though.
 
yeah wont ever need a fan if you never sit in traffic for longer than 20mins, wouldnt push your luck though on the m25 lol
 
Is your car driving ok, fuelling ok ect? It could be the coolant temp sensor not working. To check it, put the key in the ignition, turn to position 2, then unplug the coolant sensor plug (located under the coil pack in the water outlet). The fan should come on straight away. If it doesn't, it's wiring between the sensor and fan. If it does come on, then the sensor is gone and needs replacing.
 
The temp sensor is resistance based on temperature.
Coolant cold = high resistance
Coolant hot = low resistance

Pulling the plug from the temp sensor will create low/no resistance (the same as coolant hot) and would turn the fan on anyway....??
The ECU thinks the engine has gone to severe overheat so it puts the fan on fast speed.
 
PumaNoob said:
then unplug the coolant sensor plug. The fan should come on straight away. If it doesn't, it's wiring between the sensor and fan. If it does come on, then the sensor is gone and needs replacing.
I'm lost... :oops:
The fan will come on anyway (as it goes low resistance/open circuit), irrespective of whether the temp sensor is shot or not... so is this actually a valid test...?

If the fan comes on, it confirms the ECU will tell the fan to come on, which also confirms the wiring between the ECU and the sensor is ok, and the relay is also ok.

I'm not nit-picking Pumanoob... I'm interested in this as I have the exact same problem...
 
Yeah, it's definitely a valid test, the OP said that the fan is not coming on when the temps reach above the threshold. If there is faulty wiring between the sensor and fan, ie giving high or infinite resistance, then you will see this as the rad fan won't come on when sensor is unplugged, as it's still getting high resistance.

If the sensor is faulty, it will go to very high/infinite resistance, so no matter how hot the coolant gets, it will mover get low enough to switch the fan on. By pulling the plug, the circuit goes open circuit - zero resistance, & the fan comes on. That then shows the circuitry is working.

If you want to go in deeper (it means loosing some coolant), take the sensor out, and put an ohm meter across it. Put the end on a block of I've, and resistance should go up to around 1700ohms. Then put it in hot water, at 70degrees C it should be about 460ohms. 100 degrees should be around 200ohms. If the sensor is found to be working, then the coolant in the head is not reaching the sensor, meaning air lock. On older pumas, there are 2 sensors ( they are both there on newer pumas, but 1 isn't used). There's the 2 wire sensor for ecu, & 1 wire sensor for the gauge on the dash. If its a newer puma (digi dash) then the temp gauge on the clock will tell you if the sensor is faulty as it will go right up and stay there or more likely will stay right at the bottom and not move. But in older pumas, the dash is controlled by the 1 wire sensor, so the ECU and fan will see a different reading to the dash.

I hope that's a little clearer now, I don't think you were but picking mate, if I say something that don't make sense to you, it's best to query it!
 
Thanks PumaNoob, that's a lot clearer. What you wrote about the fan going on or not, didn't work out in my head, but I couldn't explain why...
So, a failed temp sensor always fails while in a 'cold' state? - I've fitted a new genuine Ford one and that's done diddley squat to the situation. The only good thing that's came out of this is the low speed fan works as it didn't before.

Can anyone say where the dash temp sensor is? Is it possible this reads higher than it should so maybe we are thinking the engine is overheating when it's not? Probably unlikely, so maybe something else to rule out...
 
TempSensordiagram-1.jpg.html


I have the resistor values of the sender sensor too, I'll get them later for you if you need them
 
That would be handy PumaNoob... thank you.

I'm not trying to hijack the thread, hopefully this will help the OP as well as me.

Just as a reference point, I've been checking the resistance values of the old temp sensor I took out (as the new Ford one has not helped, maybe the old one isn't faulty..!?)
At room temperature: 24.5ohm
80 degs: 4.5ohm
100 degs: 3ohm (could wait any longer as fingers started to burn!)
 
The oil switch isn't a heat sensor, its a pressure sensor switch. So the changing resistance is coinsidental.
 

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