Cooling fans not coming on

Soldato
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Hi all,

I have a problem with my 2001 1.6 petrol focus, where the radiator cooling fan does not come on, I have checked the fuses in the fuse box and replaced the relay too. What else do i need to check, is there a way to directly test the fans themselves (my car has two fans both fail to come on). I have a car with aircon if that makes any difference?

Also another question does the temperature gauge on the instrument panel work off the cylinder head temperature (CHT) sensor, in it if the temperature in the car instrument panel is working does it mean that the CHT sensor is working?

Thanks in advance guys :)
 
Soldato
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Can you take the fans out and see if they're seized? I had that once on a fiat Punto and it was an easy job with a few clips and an electric connector. Got the whole fixture from a breakers for £20 or so.
 
Soldato
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The temp gauge works in the car, it goes from cold to hot as the engine warms up then rises higher as you drive it.
The heater also works turning switching from hot to cold and vice versa.

Do I need to remove the fans or so I test them while they are still connected to the car?

Thanks guys
 
Soldato
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I had a knackered fan on my old Fiesta a few years back. I think it'd been knackered for a while as I only ever noticed the car reporting the outside temp as much higher than it was (reporting 35+ degrees C when in stationary traffic in Brussels in November, I think not) and then the same thing another time while stuck in traffic on the M25. I think I just didn't notice because most of my driving was motorway and I was relatively lucky with traffic so the natural airflow from that just kept it cool.

I could attempt to spin the fan by hand with it still fixed in the car and it was obviously not happy about moving. The fan was stiff and it made a horrible squealing sound so I took a punt and £40 and half hour's work later a new one was on which kicked in straight away.

Have you attempted to spin them by hand with them still in the car at all? I'd have my doubts about both fans having seized up at the same time so perhaps there is something else at play here. It does look like the MK1 Focus radiator fans are a simple 2 pin connector so a relatively simple way to check they're ok would be to use some suitable gauge cable, identify the positive and negative and connect them straight to a battery.
 
Associate
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You can try removing the relay and shorting the power feed terminals at the fuse box - this will prove out the fans themselves plus wiring from the fusebox to the fans. If they work ok shorted out (use some thick cable for this) then fault lies earlier in the system with either the sensor or wiring. If fans don't work then move to fan connection and see if putting 12V there works or not.

You may need to get your hands on a wiring schematic at some point if it's proving difficult to narrow it down further.
 
Caporegime
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Fans will not come on unless they need too. Normally one for aircon and one for radiator unless your car is more complex. If air con is broken it will never come on. Radiator will have a sensor going into it. If you unplug that it will run the rad fan 24/7. You can always check out the fans themselves by jury rigging them straight to a 12v power supply.

Also if your car is overheating only in traffic then that leads to fans but if it is overheating while driving then that is something different. Thermostat, broken rad, wrong mix of coolant etc etc. Fans have minimal effect on cooling when going over 30mph.
 
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Soldato
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The fans are both spinning/working.. I connected them both to the battery directly and they spin.
If I take the CHT sensor out should the fan(s) come on?
 
Caporegime
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The heating switches from hot to cold and vice versa... so is that unlikely to be the thermostat?

No all the thermostats job is to block the flow of coolant. When the engine heats up it opens allowing the coolant to flow round the engine. If it doesn't open up the coolant can't be cycled through the radiator and the coolant in the block will just get hotter and hotter.

The same is said about cooling fans. They do help but their main purpose is to flow air over the car when stationary. Once moving physics takes over. If your car is overheating when stationary then the fan is the culprit. If it is over heating on the move something else is at fault.
 
Soldato
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The fans are working, looks like it is to do with flow of coolant that is causing the issue. How can I test if it is the thermostat or the radiator?

Thanks for your help adam_cool_dude
 
Soldato
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i have noticed that the water in the top of coolant reservoir bottle is filling up but not emptying flowing out at the bottle of it.. would that indicate that thermostat is not opening of closing or the radiator or radiator hose is blocked??
 
Soldato
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If you want to do a quick / rough stat check then get the engine warm and check if both upper and lower rad hoses feel warm

To check the thermostat properly you'll need to take it out, at which point I'd just replace it given they're typically cheap components
 
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