Problem with cooling fan...again!

[FrenchMike]

Originally Posted by SD1too

I don't know exactly what the Revotec kit includes but of one thing I am sure; it will not be capable of decoding the PWM signal sent by your car's ECM and it is that which determines fan operation and speed. This decoding operation is performed by the MG Rover PCB so you will need that in working order regardless.

In your shoes I would have the bumper off and inspect the wiring and connectors carefully.

Simon

Hi Simon,I have modified his PCB to lower the threshold of the second speed.
I'm certain it works perfectly

As the box is easely accessible now ,he can connect the PWM command wire
to earth to force the high speed ,in case ...

Mike

[SD1too]

Originally Posted by rovertone

... the cooling fan started running at high speed whenever the ignition was switched on regardless of whether aircon was on or off ... now it seems to be 'pulsing' and occasionally stopping for a few seconds. It will then start again run up to high speed then drop back pulsing to nearly stopping,

Hi Mike,

It's Tony's description above which makes me wonder whether he has wiring damage causing this strange behaviour. I agree that it doesn't sound like anything we've come across before. What do you think?

Simon

[FrenchMike]

Originally Posted by SD1too

Hi Mike,

It's Tony's description above which makes me wonder whether he has wiring damage causing this strange behaviour. I agree that it doesn't sound like anything we've come across before. What do you think?

Simon

I think he has to observe the relation between temp coolant and fan triggering ,firstly .
Another way of investigation is at any moment control the good working

of the the 2 speeds .(remember, the simplest test is earthing the PWM line.)


Mike

[T-Cut]

Originally Posted by rovertone

I noticed a few weeks ago that the cooling fan started running at high speed whenever the ignition was switched on regardless of whether aircon was on or off.

I assumed this was when the engine was cold. Maybe I misunderstand?

TC

[rovertone]

T-Cut That is correct fan performs that way from cold. It also seems to be erratic. I have just driven 30 miles today towing caravan and I set the OBD so I could moniton temp.
Most of time it was 89/91 rising up to 103 on one climb but soon dropping back again, tried to listen for fan but couldn't hear it over engine.
When I arrived fan was running normally, slow speed, Aircon on!

I hear what's being said re wiring chafing, when I did the gold resistor mod I tried to take care re wiring. But it does sound a plausible cause.
When I get home I will double check including the resistor joints.
Thanks to all for input
Tony

[SD1too]

Originally Posted by rovertone

Most of time it was 89/91 rising up to 103 on one climb ...
When I arrived fan was running normally, slow speed, Aircon on!

Tony, I'm beginning to wonder whether you have more than one fault here. I have no experience of towing but 103° with the fan running from an engine renowed for low production of heat?

Do you lose any coolant? Are your expansion tank cap 'O' rings flat?

Simon

[Arctic]

Hi Tony.
You know I am not to far from you, so if at anytime you need help drop me a PM I am sure we could sort it out between us, also a T4 is available, I have plenty of relays, I recently replaced a gold resistor which had blown out the coil, due to water ingress maybe a joint is getting wet ? get your bumper off and check the wiring from the resistor, also wiring back to the look plugs. Arctic

[rovertone]

Simon
Under normal driving everything is fine.
Before I changed pump and stat 'normal' running temp was high 70's I did ponder on whether to change or not thinking better to keep cooler engine for towing however I went ahead for sake of being sure pump was sound and to be honest it hasn't made much difference on how the temp rises on climbs with van on.

I have run through hot climes without caravan with OBD readings and temp rarely moves out of 89/91 range with new stat.
It seems that the engine (mine) is OK under normal circumstances but heats up quickly when working hard.
Without seeing the OBD readout I would be none the wiser. However whilst I.am happy towing generally, I am not confident taking on long continental climbs. Earlier this year I drove west from Spain to Porto on the motorway and I was very pleased I didn't have van on, it was like a roller coaster!

In reality I guess it's only a minority of cars that have exposed to such conditions so that's maybe why problem hasn't arisen. I wonder if BMW's with this engine variant have ever reported problems. Maybe it's radiator sizing/engine orientation related.

I am not planning any more long trips into the high hills so maybe I won't be troubled, but it is interesting.
For now I'm going to focus on fan and black smoke (another thread) what's frustrating is that the car runs really really well.
Cheers Tony

[T-Cut]

Originally Posted by rovertone

T-Cut That is correct fan performs that way from cold. It also seems to be erratic.

This isn't normal and suggests an electronic fault IMO.

Most of time it was 89/91 rising up to 103 on one climb but soon dropping back again

Work a diesel hard and it will warm up, of that there's no doubt. The new stat is doing a good job IMO.

TC

[rovertone]

Originally Posted by Arctic

Hi Tony.
You know I am not to far from you, so if at anytime you need help drop me a PM I am sure we could sort it out between us, also a T4 is available, I have plenty of relays, I recently replaced a gold resistor which had blown out the coil, due to water ingress maybe a joint is getting wet ? get your bumper off and check the wiring from the resistor, also wiring back to the look plugs. Arctic

Many thanks for your offer Steve,
I'm going to do exactly what you say when I get back, it does seem like an electrical connection problem.
I'm also going to fit one of Jules' silicone intercooler hoses for my other problem.
Cheers
Tony