75 Diesel Rad Fan Mod

[boofs]

Hi,This might be best answered by Dee Cee any way here goes I noticed that my wipers detected when the car stops and starts by the wipers stopping and starting on the second stalk posistion,I take it this means that the ECU controls the wipers so must have the siginal input to tell it to stop the wipers when car is stopped and start them when the car pulls away,My question is can this car stopped car start signal which controls the wipers via the ECU be used to control a relay to control the rad fan slow speed to switch on when car is stationary and off when car is moving this will prolong the life of the rad fan motor,Regards,Tony @ Totnes, Devon, UK.

[Phil]

Just wondering, how would that prolong the fan motor life? Surely, if you were stop starting all the time it would damge the motor due to stop, starting all the time. I may be wrong, however.
When i'm stuck in traffic, I always stick the a/c on to allow the condenser fan to run.

[boofs]

Hi,
The reason it would save the rad fan motor is because the rad fan is running all the time when the climate control air con is switched on and if like me you have the climate control on perminant then the rad fan (common earth brush wears away) will only last 20k+ miles,
Therefore as the fan only needs to be on when the car is stationary and not when the car is moving it usefull life would be greatly extended,
Regards.

[Phil]

I see what you mean now. Please excuse me. I'm easily confused. Not sure what I was thinking!:getmecoat:

[Keith]

We considered using the ABS signal to turn the fan off when on the move but it is not fool proof as if you have a strong tail wind the condenser could still be in static air

Instead we used a mechanical airflow sensor with built in discrimination for false positives during braking and acceleration etc

The prototypes that Dee Cee and I have were both for the CDT so the electronics are a little more complex as they manage the PWM circuit. Building one for a petrol engined cars would be a bit easier although then you have two relays to manage, controlling the high speed relayy would not be a good idea as that could prevent adequate engine cooling

Note though the Diesel is a cold running engine so there are real benefits to be had in managing the fan on the move.
I am not 100% sure I would want to do the same for the petrol car as those fans spend a higher proportion of their life cooling the engine and you would probably find disabling the low or medium speed simply causes the high speed to kick in a bit sooner.

[Mike]

the rad fan is running all the time when the climate control air con is switched on and if like me you have the climate control on permanent then the rad fan (common earth brush wears away) will only last 20k+ miles,

I know these fans can be a problem but it's not the same for all 75's. My fan has run 6 years and 60k miles with no issue and I use air con all the time (touches wood and fingers now firmly crossed ;) )

[billnick]

Kieth, what is the status of the fan when you run in econ mode ?

regards bill.

[madone]

Must admit since having to change mine last summer I now use the econ whenever I can. I will only use it for the warmer months or if the side windows steam up, hopefully prolonging its life.

[billnick]

thats what i had in mind.

[Keith]

In Econ mode the Aircon is permanently off so the fan will only run when under demand for normal engine cooling.

I run my V8 and CDT in Econ until the temperature gauge gets up to normal unless I need aircon assistance for demisting then I switch back to Auto. I find even without my FBH going in my CDT that I get a much faster engine warm up that way.

I don't necessarily need to do this with the V6 in my ZTT as that warms up (water wise) much faster.

[boofs]

hi,
Can someone advise me how exactly the electronics works ? from the ABS which controls the wipers 2nd speed to stop when the Vechicle stops so I can experiment with a rad fan slow speed control relay using the wiper stop control pulse from the ECU,
Regards,
Tony, @ Totnes, Devon, UK.