Rover 75 Con SE 2.0 CDTi - Radiator Cooling Fan Always On

[cashford]

Hi All

I know there have been many posts on this in the past but most seem a long time ago so I thought I'd ask what might be the same question again as the 'fix' options might be different now.

In the last few days the radiator fan has starting coming on just a second or two after switching on the ignition (engine does not need to be on) and remaining on the whole time the car is running before finally stopping about 5-10 seconds after the ignition is turned off.

Based on all the posts I have found I have done ... listed below, I think it's probable something to do with PCB or relays mounted in the side of the radiator fan housing.

I have not had the front off the car yet, but from peering through the grille it seems my radiator does NOT have a resistor on it.

The tests/checks I have done are:

1. Air con off and in Econ mode.. Fan stays on. Air con/Fan switched completely to off... Fan stays on. Front Demist switched on... Fan remains.... Basically no impact whatever I change there.

2. Fan seems to just come on irrespective of whether the engine is running or not but does stop shortly after the ignition is switched off.. From what I've read this seems to rule out a relay in the PCB module being stuck

3. Checked connections behind OSF headlight so signs of water ingress.

4. Checked the dashboard display diagnostics to check temperature is being read correctly by the sensor... starts off about 10 degrees (probably right of the weather now) and rises as the car is driven to about 90 ish

5. Temperature gauge on the dash also works as you would expect and ends up at the 9 O'Clock Position so probably not the Temperature sensor on the engine

6. Disconnected the Aircon Trinary switch to see if the fan stopped or sped up... no impact... just kept running

So based on the fact that there appears to be no resistor I think it must be the radiator fan PCB, or possibly (I think I have read) the PWM signal wire?

I guess my questions are simply this... I am no genius .. indeed all I have done to get this far is follow other posts on the forum so...

Do you guys who are far cleverer than me agree with my thoughts?
Do you have any other suggestions
Most importantly, if you do agree with me... Does anyone know how I can get the PCB repaired.... I see there have previously been some members that can help here but the posts were very old, so hence the reason for asking the questions afresh.

Thank you all so much.

CHARLES

[SD1too]

Originally Posted by cashford

Most importantly, if you do agree with me... Does anyone know how I can get the PCB repaired....

Hello Charles,

Club member FrenchMike is your man for the diesel PCB. Years ago he explained to me how it worked at component level and has occasionally repaired them for club members. After a quiet period I think I saw a post from him only a few days ago so try a message or an e-mail.

Simon

[cashford]

Hi Simon

Thanks for this.. I'll PM him right now. Appreciate the info

Charles

[cashford]

Quick question - It's going take me a few weeks to have time to get this fixed... Can I drive the car normally while the fan is just running all the time... I'm guessing it will be fine but just wanted to check with people wiser than me!

Also, if I can't get a replacement PCB or a repair, is there a way I can replace the whole fan assembly with a different type, IE the type with the resistor or will this require other changes too?

Thanks Again

CHARLES

[Arctic]

Hi Charles.
You can change the fan over with one the same, r one with the gold resistor it will be plug and play, if you were closer to us in the West midlands we could have checked this out for you this weekend at our meet, Saturday.

I carry spare refurbished fans with me at the meet, i also have a couple of unobtainable PCB boards, i have not heard from French mike for ages i have five PCB that need sorting out, but have also contacted another chap local to us whom may be able to help with sorting out the PCB, waiting on his reply.

Driving the car with the fan on all the time will only wear out the brushes quicker, it should not do any other harm, same goes if you remove the fuse to the fan and it does not run at all, i doubt you will over heat a diesel unless maybe it was very hot summer and you were towing a caravan.

Either way you will need to get to the black relay box with the relay's and PCB in.
1

https://www.midlandsnanomeets.co.uk/meets_2014.html

[cashford]

Hi Acrtic - Thanks for the reply... I didn't know about the NanoMeets... They sound brilliant! I'll deffo come up for one, sounds like a good day out and a good excuse to take my old girl (The 75 that is, not the wife LOL!) on a decent drive.

Re the PCB, are you saying you have a working spare? If so could you PM me to see if we can sort something out? - You could be my saviour!!! Just need to get to mine first LOL!

Do you think reading through the tests I have done and the results that it is most likely the PCB at fault?

Thanks again - Charles

[WillyHeckaslike]

FenchMike's profile shows that he has not logged in since 26th July 2022 and I think that at least one member has since tried to contact him to no avail. He was a regular poster so his absence of 20 months to date could suggest that he is either taking a break from the site or that he is no longer available for whatever reason.

[Arctic]

Hi Charles.
Yes i have read through what you have tested, so just reiterate, with the A/C completely off no econ etc on, when you start the car the cooling fan at the front runs continuously, only when you turn the engine does it stop running after a while.

Also you need to check the near side wiring fan connections to the main loom access is with the bumper removed.
1

Check these connections for water ingress, unplug them check spade ends for corrosion, spray with electrical contact cleaner and refit check the fan again, this can be done with the bumper off.

You would need to remove the slam panel to get to the relay black box.
2

Four wire 3 speed fan should have M47 printed on the front of the relay box, and would look like this below inside.
3

The two wire 2 speed fan should have PWM2 printed on the box and look like this inside.
4

5

Please check the above and then drop me a PM with regards to the PCB/ fan cheers Arctic.

[cashford]

Hi Arctic

Thanks for the reply, that's amazing really appreciate the time you've taken on that.

Your synopsis of my testing and results is spot on.

As soon as we get a nice weekend I'll take the front end off and have a look and PM you. Hopefully it will be this week as it's Easter but looking at the weather forecast I fear it may not be.

For now, indeed this morning, I took the 80A fuse out as I think our climate at the moment is hardly aligned to aggravating overheating so fingers crossed it'll be OK.

Thanks again. I'll PM you hopefully shortly

CHARLES

[cashford]

Hi

Front of the car off... I didn't have to do battle with too many rusty screws/bolts, indeed I have to sat I was really surprised at how little rust there is around the front end.

Anyway, I have got access to the relay/PCB box and it looks like I have the four wire 3 speed fan and deffo no resistor on the fan housing. It all looks really clean, no obvious signs of water ingress and the multiplug connectors on the near side were also really clean and dry but I sprayed some electrical contact cleaner all over them anyway.

I realise I can't see anything by looking at it, so I guess my question is now, where do I go from here. Do I assume it is he PCB that is faulty and try and source one?

I can't work out how to attached photos to my post :-(

Thanks all again for all your help, especially the 'how to guide' for removing the front end.. I would never have done it without that... Just somehow need to get it back together again Eeek!