Fan constantly running

Wuggis · 16th August 2018, 18:50

So I got home the other day after dropping my daughter off at home. And when I got out of the car the fan was doing its jet engine preparing for take off impression.
Nothing unusual about that especially if I've been running the Aircon which given the recent weather I've been doing non stop.

However after making a brew and having a chat with my wife I went back outside and found the fan still running flat out. And since then the only way to stop the fan is to disconnect the battery.

I've tried the simple fixes relay, coolant temperature sensor etc. But have had absolutely no effect on the situation. I know a similar question was asked here some time back. But as far as I can see it was never resolved.

At the moment I'm thinking I'm going to end up replacing the fan. But is there anything I should check first.

trikey · 16th August 2018, 19:59

Sounds like a sticking relay inside the control box (On the fan shroud - next to the fan)

RoverDan · 16th August 2018, 22:59

Also look closely at the wiring in the control box; one of mine did this because the wires had been crossed then compressed as the box was reassembled at some point, leading to a short over a spade connector.

Arctic · 17th August 2018, 01:01

Quote:

Originally Posted by Wuggis

So I got home the other day after dropping my daughter off at home. And when I got out of the car the fan was doing its jet engine preparing for take off impression.
Nothing unusual about that especially if I've been running the Aircon which given the recent weather I've been doing non stop.

However after making a brew and having a chat with my wife I went back outside and found the fan still running flat out. And since then the only way to stop the fan is to disconnect the battery.

Quote:

I've tried the simple fixes relay, coolant temperature sensor etc. But have had absolutely no effect on the situation. I know a similar question was asked here some time back. But as far as I can see it was never resolved.

At the moment I'm thinking I'm going to end up replacing the fan. But is there anything I should check first.

I would say it is the PCB board, do you know if it is a four wire 3 speed fan or a two wire 2 speed fan with a resistor, you can check this by looking through the front grill and through the fan blades at about 2.0 Oclock .

Wuggis · 17th August 2018, 14:23

Just my luck I can't see anything through the grill. Is the relay replaceable on the control unit? Or is that definite a new fan?
I'll be having the front bumper off tomorrow to investigate so I'll know which type I have then. The car is a 2005 diesel if that helps

Wuggis · 17th August 2018, 14:38

Just managed to see it's the type with the big resistor visible at the 2 o'clock position

suzublu · 17th August 2018, 15:33

Get one of these from Jules https://www.the75andztclub.co.uk/for...ad.php?t=68336

Wuggis · 17th August 2018, 16:17

Thanks for your help. Much appreciated.
And my neighbours will thank you every morning at 5.30 am

T-Cut · 17th August 2018, 17:50

A failed low speed resistor isn't the cause of the constant fast running fan. The resistor provides the low speed circuit - which might well be faulty as well, but it doesn't cause your symproms.
Two common causes have been proposed (stuck high speed relay and a faulty printed circuit board). The circuit board issue is very common in diesels and a repair service is available. These and other faults are all more likely than the resistor. By all means swap the poor OEM resistor if you can see one, but it won't fix the uncontrolled high speed running.

TC

SD1too · 17th August 2018, 19:13

Quote:

Originally Posted by Wuggis

Or is that definite a new fan?

It’s definite that you do NOT need a new fan Craig! Nor will a gold resistor cure your problem as T-Cut has helpfully pointed out. I bet the relays will be fine too. The most likely cause is the PCB (Printed Circuit Board) inside the control box. It’s too clever for its own good! Fortunately FrenchMike can repair it for you.

Simon

16th August 2018, 18:50	#1
Wuggis Newbie Mg zt Join Date: May 2016 Location: Walsall Posts: 7 Thanks: 0 Thanked 0 Times in 0 Posts	Fan constantly running So I got home the other day after dropping my daughter off at home. And when I got out of the car the fan was doing its jet engine preparing for take off impression. Nothing unusual about that especially if I've been running the Aircon which given the recent weather I've been doing non stop. However after making a brew and having a chat with my wife I went back outside and found the fan still running flat out. And since then the only way to stop the fan is to disconnect the battery. I've tried the simple fixes relay, coolant temperature sensor etc. But have had absolutely no effect on the situation. I know a similar question was asked here some time back. But as far as I can see it was never resolved. At the moment I'm thinking I'm going to end up replacing the fan. But is there anything I should check first.

16th August 2018, 22:59	#3
RoverDan Avid contributor Rover 75 Saloon, Tourer, Limo Join Date: Feb 2011 Location: Exeter Posts: 233 Thanks: 52 Thanked 82 Times in 51 Posts	Also look closely at the wiring in the control box; one of mine did this because the wires had been crossed then compressed as the box was reassembled at some point, leading to a short over a spade connector. __________________ -- CDT auto Club Saloon CDT auto Connoisseur SE Tourer CDT auto Connoisseur MacNeillie Limousine

16th August 2018, 19:59	#2
trikey Premium Trader Rover 75 Join Date: Nov 2010 Location: Devon Posts: 33,766 Thanks: 8,837 Thanked 14,831 Times in 8,030 Posts	Sounds like a sticking relay inside the control box (On the fan shroud - next to the fan)

17th August 2018, 14:23	#5
Wuggis Newbie Mg zt Join Date: May 2016 Location: Walsall Posts: 7 Thanks: 0 Thanked 0 Times in 0 Posts	Just my luck I can't see anything through the grill. Is the relay replaceable on the control unit? Or is that definite a new fan? I'll be having the front bumper off tomorrow to investigate so I'll know which type I have then. The car is a 2005 diesel if that helps

17th August 2018, 14:38	#6
Wuggis Newbie Mg zt Join Date: May 2016 Location: Walsall Posts: 7 Thanks: 0 Thanked 0 Times in 0 Posts	Just managed to see it's the type with the big resistor visible at the 2 o'clock position

17th August 2018, 15:33	#7
suzublu This is my second home rover 75 1.8 vvc club se wedgwood blue Join Date: Aug 2009 Location: Seaton Carew Posts: 26,918 Thanks: 65 Thanked 7,142 Times in 4,642 Posts	Get one of these from Jules https://www.the75andztclub.co.uk/for...ad.php?t=68336

17th August 2018, 16:17	#8
Wuggis Newbie Mg zt Join Date: May 2016 Location: Walsall Posts: 7 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks for your help. Much appreciated. And my neighbours will thank you every morning at 5.30 am

17th August 2018, 17:50	#9
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,752 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	A failed low speed resistor isn't the cause of the constant fast running fan. The resistor provides the low speed circuit - which might well be faulty as well, but it doesn't cause your symproms. Two common causes have been proposed (stuck high speed relay and a faulty printed circuit board). The circuit board issue is very common in diesels and a repair service is available. These and other faults are all more likely than the resistor. By all means swap the poor OEM resistor if you can see one, but it won't fix the uncontrolled high speed running. TC