Radiator fan not kicking in

[JW-172]

On my 172 PH2 the rad fan doesn't come on as I discovered when it overheated during MOT . The temp gauge works fine and sits at a constant level when driving, doesn't shoot up when waiting at the lights etc. I've sent a 12v current to the fan and it comes on fine. There's no loose/dodgy wires that I can see. Checked fuses and none are broken/corroded. I've read a few threads about it but there doesn't seem to be many answers. There's a small grey plug near where I presume the fan switch goes, but I was told PH2's don't use the switch? Odd as the plug for it is there (I think)

 

[tom_k4j]

Are U sure colant temp reached the point where the fan turns on (99stC on K4J, on Sport probably the same)? If unsure do the following: turn off ignition, disconnect coolant temp sensor (located at the thermostat casing), turn on ignition or even start engine - now the fan should turn on regardless of collant temperature (ECU precaution behavior). If it's not working use multimeter to check if there is voltage on the fan connector. Besides fuses there are also two relays for fan (low speed, high speed), have you checked them?

All above information is based on Clio2ph2 K4J but those should also apply to your version.

 

[JW-172]

I've tried unplugging the coolant temp sensor whilst the engine was running but the fan didn't kick in. I will double check the fan connector again today, but then surely that will only get power when the relay switches? I'm going to get some 5amp wire and clips to test the relays today, I've looked at the diagrams on google such as:
http://s69.photobucket.com/user/tomp1988/media/mike1.jpg.html

But this only shows 1 large relay, with 4 smaller ones? My 172 has 3 larger ones (one brown, two black) and 3 smaller, this is mine:

(ignore the circles)

The only thing I've managed to decipher is the middle smaller relay controls the engine start? Be really helpful if someone could tell me what the others do.

 

[JW-172]

I also noticed this hanging down by the rad:

But doesn't seem to plug into anything?

 

[tom_k4j]

You should try doing exactly as I advised, disconnecting coolant sensor while engine is running won't trigger fan start, you have to switch ignition off, disconnect, then turn ignition/engine on. If afterwards fan is not spinning then you can be sure something's rotten. In my Clio those two small relays next to the circled one are for fan: one for low fan speed, second for high fan speed. If you don't have manual for your car and not sure which is for, just check all relays are ok, the we'll be able to search the problem cause further.

I don't know what that free hanging plug might be for, at mine's there isn't such and the fan connector has only two pins and is oval in shape.

 

[JW-172]

I'll give it a go now. Are any of the larger relays for the fan?

 

[JW-172]

No luck with unplugging the sensor. The bases to the relays are getting a good current, so can I assume there's either a dodgy relay or a break in the wiring between the relay(s) and the fan plug?

 

[tom_k4j]

I'll give it a go now. Are any of the larger relays for the fan?

Dunno, find a proper manual to figure that out.

The bases to the relays are getting a good current, so can I assume there's either a dodgy relay or a break in the wiring between the relay(s) and the fan plug?

By checking the relays I meant testing if their coils are ok (google should give you a good basis on how to check a relay).

On each coil there is a scheme, if you are able to read it you can short circuit appropriate pins in the relay socket to test if the fan will start - that will tell you if the wiring is ok. Before that you can measure the voltage on those pins, should be ~ 12V. But do it only if you are sure what you are doing. Provide picture of the relay scheme inprinted on it so i can give you a hint.

 

[JW-172]

Ok, I know what you meant by testing the relays, was just mentioning that power is getting to the bases of the relays. According to this:
http://www.getflat.co.uk/pics/PLATFUSI-14.pdf

One of the bigger relays does control the fan (relay A). So one of the larger ones for high speed, then a smaller relay (E) for the low speed? As mentioned, I'll get some test wires made up later and test the relays with 12v and a multimeter. Should give us a better indication of what's going on

 

[tom_k4j]

My guess is your Clio doesn't have aircon right?

 

[JW-172]

Mine has aircon. I don't see the fan coming on when A/C is on

 

[Dan@SJM]

Bridge the relay and see if that works

 

[JW-172]

Bridge the relay and see if that works

Will do, if it doesn't turn on the fan can I assume there's a break between the relay and the fan plug?

 

[Dan@SJM]

Assuming you have 12v at the relay yes

 

[JW-172]

I'm getting like 12.4 I think at the relay bases

 

[Dan@SJM]

Sounds good

 

[JW-172]

Finally got the time to try bridging the relay today. I tried the smaller relay on the right in the above pic. The middle one is for the starter, left is something to do with the throttle body (when I unplug it the throttle body stops buzzing) so the right one must be one of the fan speeds. No luck. The other two bridge fine. So hopefully there's just a break between the relay and the fan plug.

 

[tom_k4j]

Well not necessarily, it could be anywhere. Did you measure the voltage on those pins You bridged?
Few things to check:
+voltage as in above question
+check if there's a ground on the fan plug (on one of the pins)
+check if there's connection (with multimeter) between one of the fan plugs and the appropriate pin in relay socket
+check if there's voltage on the other pin than above in the relay socket

 

[JW-172]

As said above, voltage is approx 12.4v at the relay base. Fan plug wires are connected properly at both ends.

 

[JW-172]

I'd like to report that the problem is fixed but I can't Today I stripped all the trunking and tape off the wires going from the radiator plugs and traced them back to the relay board, no breaks, took all the relays out and tested them, all were clicking with 0 resistance, all the relay bases are getting 12.7v (ignition off). I then tried disconnecting the coolant sensor and bridging the fan relay base then turned the car on, no joy. So confused. The fan itself works, there's power to the relays, the relays work and there's no break in the wires between the relays and the plugs.

 

[Dan@SJM]

So it's on the switched earth to the ecu.

 

[Sean6545]

As above. The earth from the ecu to the relay is open circuit.

 

[JW-172]

What do you mean folks?

 

[Dan@SJM]

Ecu switches earth to trigger the relay. That's where your fault is.

 

[JW-172]

So what should I be looking at next? As you can tell I'm a bit of a noob with auto electrics but would rather try and learn before sending it to the garage.

 

[Dan@SJM]

A break in the wire between the ecu and the relay

 

[JW-172]

I'd checked all the wires when I was trying to find an immob fault (turned out to be an earth strap). I'm going to do a manual setup for the time being and then after Xmas get it on clip and see what's going on properly

 

[Dan@SJM]

So you've already checked the ecu line to the fan relay? Does it give a supplied earth when the cts is unplugged?

Clip won't tell you anything about a relay fault, will only say about a circuit error

 

[tom_k4j]

I assume you've already checked two fan fuses that are in the fan case inside the car ? :>

 

[JW-172]

Fuses have been checked a thousand times haha

 

[tom_k4j]

Just out of curiosity: how things are going? Any updates?

 

[Le Baguette]

I have the same issue but haven't had time to investigate further.

Did you ever find out the cause?

 

[Keithvfr]

I also noticed this hanging down by the rad:

But doesn't seem to plug into anything?

Hi that plug is the one that goes to the aircon pressure switch

 

[Gilko172]

I assume you've already checked two fan fuses that are in the fan case inside the car ? :>

Is this in the fuse box at the passenger door or somewhere else? I have this exact issue with my 172 cup and can't figure out the source of the problem.