2 Speed Fan Poser will my woes end!

[rovertone]

Hi Pete,
Your recap is spot on.

Can you advise me where I could source the correct PCB and relays, electronics is not my forte

Maybe a complete new fan and control box from Jules would be a solution, albeit more costly.

I will be flushing the system again, and because of the solo cool running, replacing the stat and may as well replace the pump for good measure (108k on clock) given I hope to be towing back and forth to Portugal twice a year.
I have had the heater matrix out and flushed it through with boiling water a few times, the heater does work ok. My concern is not being able to get a good flush with the thermostat in and/or whether I clear everything out of the engine. The radweld product was only in for a very short time (1 mile) before the system was drained to fit the new rad so hoping it didn't get too much chance to gunge up.

Thanks for your input
Tony

[SD1too]

Originally Posted by Union Wheels

No fast speed when engine temperature sensor disconnected (only slow speed) ... Logically therefore the pulse width modulator signal to trigger high speed is not working, missing or low in amplitude.

The trouble is Pete, Tony has posted this:

Originally Posted by rovertone

On my way home on occasions I heard the high speed fan come on ...

I would suspect the printed circuit board in the fan control box is faulty ...

Tony has just earthed the PCB input and heard both relays operate, so the electronics works in those circumstances. If you're suggesting that the PCB isn't recognising the high speed PWM command, then how does it work properly under test with T4?
Sorry, it's unsafe to conclude that the PCB is faulty.

My other suggestion would be an intermittent high speed relay (burnt contacts) ...

The relay has just been proven.

Originally Posted by rovertone

Can you advise me where I could source the correct PCB and relays ..

You have got the correct PCB and relays. I can see that from your photos and your test.

Maybe a complete new fan and control box from Jules would be a solution, albeit more costly.

Your problem is not the fan!

... because of the solo cool running ...

What does "solo cool running" mean please Tony?

Simon

[Union Wheels]

Hi SD1too,

I think you are assuming that a T4 test for high speed fan adjusts the duty cycle of the pulse width modulator. This may be the case, but it could also use another path to check the fan runs at high speed.

An intermittent relay is just that, it may not work all the time, and the fact that you can hear it click does not mean it will pass current.

You must also consider the fact that high speed is not achieved when the engine temperature sensor is unplugged, and replacing the P.C. board would rule out the possibility of a faulty board.

Pete.

[Dragrad]

Threads merged at the request of the OP.

[Union Wheels]

Hi rovertone,

your best chance of obtaining a printed circuit control panel is to contact "Arctic" on this forum he is the man who has done a lot of work on fans and seems to have many spares.

Pete.

[rovertone]

Solo driving without the caravan its 79/81, peaking at 84/85. In Portugal with temps in the 30's it wasn't much different.

To clarify my comment re hearing the 2nd speed fan, that wasn't in relation to any high coolant temperature, on one occasion it was when we were without the caravan, given my subsequent findings this was likely due to aircon overheat thus triggered by trinary switch.

We have to put this problem in context, I travelled c 3600 miles towing and had I been using only the temp gauge I would have only seen it move above normal about 6 times, 4 of those where I was in an overheat situation that cut engine to 'safe mode'.
With the benefit of greater knowledge, on the return journey I travelled with the OBD display and although I only had 'safe mode' on one climb I noted that the temp gauge did run into the 100's but given it didn't exceed 115C the gauge would have stayed 'normal'. Each time when the engine load eased the temp dropped back (high 80's/90's). Ambient temp was mostly high 20's/30's and I likely had a hot condenser.
To me this suggests that the running temps given the load are there or thereabouts and the cooling system must be working reasonably well but lacks that extra boost of air at extremes when road speed is lower.
I still maintain engine temps would be expected to reach such levels under certain circumstances otherwise why would Rover have put a progressive fan system in place.

If my view is wrong what engine temperatures should I be seeing in such a scenario? If all else fails I will have to put in a 'botch' switch and see what happens next trip. That's if Mrs Rovertone will chance it again, she's been looking at V70's!

[SD1too]

Originally Posted by Union Wheels

I think you are assuming that a T4 test for high speed fan adjusts the duty cycle of the pulse width modulator. This may be the case, but it could also use another path to check the fan runs at high speed.

Pete; if you look at French Mike's drawing of the PCB circuit, there is no other way (other than creating its own PWM signal) that T4 could trigger the relays. If you can think of another path, please let us know!

An intermittent relay is just that, it may not work all the time, and the fact that you can hear it click does not mean it will pass current.

In theory I agree, but in practice automotive relays are extremely reliable.

You must also consider the fact that high speed is not achieved when the engine temperature sensor is unplugged ...

Actually this is an assumption. I quote from RAVE on the diesel's engine management system:
"In the event of ECT failure, the ECM ... will also run the cooling fan when the ignition is switched on to protect the engine from overheating."
Note that it does not specify high speed.

So the evidence does not prove that there is a fan fault.

Tony; having said that you heard the high speed fan operating, you're now speculating that this was "likely due to aircon overheat". I'm afraid that guesses like this are useless when it comes to reliable fault diagnosis.

Similarly you say that you "likely had a hot condenser". Speculation again with no facts to back it up.

I say again, it seems to me that you have an inefficient cooling system. I am satisfied that your fan is working on both speeds, but it's most likely that the additives put into the cooling system are causing irregular overheating effects which are virtually impossible to predict reliably. Indulging in bodgery by installing switches to activate faster fan speeds is not the answer.

Your thread is, I'm sorry to say, beginning to read like a "wind up".

Simon

[rovertone]

Simon
My view on the aircon overheating was based on the fact that when I returned home I discovered that at idle the fan was cycling between 1st and 2nd speed with the aircon switched on. The HP pipe within 10 secs of switching on the aircon was too hot to touch, hence i replaced the condenser, problem now solved. This failure must have built up over a period of time so I think my assumption on why I heard the fan was sound.

I am sorry you think this is a wind up, I can assure you it is not and I resent that remark. I don't go spending the thick end of £100 on a rolling road on a whim chasing a figment of my imagination.

I have worked around cars long enough to know my way round and have solved many problems.
I have found it frustrating that you keep telling me that the problem is with my cooling system and seem to want to disregard the fact that my fan has no bearing on temperature. At high temperatures 2ND SPEED IS NOT WORKING!

Thanks for you input and advice I'll progress as I see fit till I eventually solve the problem.

[RayH]

Originally Posted by SD1too

Actually this is an assumption. I quote from RAVE on the diesel's engine management system:
"In the event of ECT failure, the ECM ... will also run the cooling fan when the ignition is switched on to protect the engine from overheating."
Note that it does not specify high speed.

We do know this from my car though.
With the sensor disconnected the fan runs at high speed

Originally Posted by SD1too

So the evidence does not prove that there is a fan fault.

115 on the dyno and no high speed?

What other evidence is needed Simon?

I did refer to these points in this post but it seems to have been overlooked.

[SD1too]

Originally Posted by RayH

We do know this from my car though.
With the sensor disconnected the fan runs at high speed

Morning Ray, and thank you for this. I take it then that you've satisfied yourself that you're not hearing the low speed which can sound so noisy on a 2 speed system that it's easily mistaken for the high speed? This has happened, more than once, and I've heard 'resistor' slow speed fans running on the KV6 and I would have guessed that I was hearing fast speed.

But there's another point to consider. What is being suggested is that the ECM is providing a PWM signal limited to low fan speed operation, irrespective of the input from the coolant thermistor. If true, that would be a unique fault condition, and would need to be proven using an oscilloscope.

115 on the dyno and no high speed?
What other evidence is needed Simon?

The problem I am having Ray is that we've now reached 139 posts and Tony has provided an awful lot of evidence, scattered hither and thither, making it difficult (for me, at least) to get a clear picture. However, I have trawled through the thread again and found this in response to your question: "115 on the dyno and no high speed?"

Originally Posted by rovertone

... the key factor on the dyno was that with the auxillary high velocity fan blowing it didn't overheat, it got to 105deg ...

So, as I understand it, the dyno operator had a high power fan directed at the radiator to provide cooling. With this, Tony says that the temperature reached 105° not 115°. Now, I may have missed another post which supports your point, so if you can find one please quote it!

My second point is that, if Tony's cooling system was working properly, his slow speed fan should keep the temperature below 100°, and it does:

Originally Posted by rovertone

Under no load conditions I have proved that at 97deg the 1st speed pulls temp down immediately.

Tony also says

Originally Posted by rovertone

The engine runs too cool solo (79/81)

By "solo" Tony has explained that he means 'not towing his caravan'. Now, that's more like the temperature we would expect from a diesel isn't it?

So, Tony's temperature varies widely from the cool running we would expect to sustained 105° even with forced fan assistance. I should have noticed this trend before, so thanks Ray for persisting with questioning me, but this indicates that Tony's cooling system isn't pressurising. This can result from worn expansion tank cap sealing rings or a loose hose connection or maybe a leaky bleed screw. The cause won't be quick or easy to find, and for goodness sake don't put sealing products into the coolant , but this is where I believe Tony's efforts should be concentrated.

If you're still unconvinced, consider spyder's account of the same conditions that Tony experienced:

Originally Posted by spyder

Just been towing my 1400 odd kg van following cars doing 40 up some steep hills. Temperatures were around 86-93 and once saw 102. It came down very quickly.

Note that the temperature "came down very quickly" at 102°. That's slow fan speed territory, not high. Tony's slow speed fan isn't bringing down the temperature from 105°. It isn't even reducing with the dyno's high velocity fan, which is probably far superior to the car's own high speed fan. Doesn't that show that fan assistance is not the problem Ray?

Regards,

Simon