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Non functioning Cooling Fan

J

jemstone29@hotmail.c

New member
Hi All, my 1985 lux does not appear to have any cooling fan. I've let the temp creep up to the red line and no fan has kicked in.

Having read Clark's guide on fault finding, I have uncoupled the two wires from the temp switch in the top of the rad and nothing, both with ignition off which i understand to be low speed nor ignition on high speed. I have replaced the fuse on the board and have done the diagnostics on the relay and this works fine. When I jump the two fan wires I get a little spark so know that power is getting there so I have bought a new second hand fan to replace the one that I don't think is working.

Now my question (sorry for taking so long to get there) is does the slow speed fan resistor if failed stop the fans from working at high speed, I'm not sure from reading the clarks article. ?

I'm sure it is the fan as it is pretty stiff to turn by spinning with the finger with lots of resistance , is this normal or should it spin easlily ?

Cheers as always for the responses

Jeremy
 
Generally, fans should spin very easily with little to no drag from the motor. You might get some temporary relief by spraying the motor internals and the fan bearing with some color tv cleaner which does a great job of dissolving dried up lubricant caked with dirt and other sticky substances that electric motors tend to create over time.
 
A short explanation may help others understand how the cooling system works .

The cooling fan on the early (non AirCon ) cars has 2x power supplies and 2x speeds.

A constant 12v+ supply is provided from the battery, direct to the fan motor at all times even with the ignition off.
It is fed through the fan fuse No3 and then via the fan resistor which reduces the current and thereby slows the fan speed .

Provided the coolant temperature is hot enough ,the temperature sensor switch in the radiator completes the circuit by earthing the fan motor. The cooling fan will then run continuously with the ignition off until the sensor switch disconnects the earth supply to the fan motor when the temperature reduces.

The second 12v+ supply also comes from the fan fuse but via the fan relay as soon as the ignition is switched on.

Both 12v+ supplies now arrive simultaneously at the same place ( ie the fan motor.) However the 12v+ from the relay over-rides the supply from the resistor, giving full current to the fan motor . Provided the coolant temperature is still high the rad temperature sensor switch, earths the fan motor, which will run at full speed whilst the ignition is switched on but will switch to slow speed when the ignition is switched off.

When the temperature drops sufficiently the rad sensor switch disconnects the fan motor earth connection.

Hope that this explanation will help others understand how the system works and assist with fault testing.
later cars and those with AirCon achieve the same operation but with modifications and slightly different circuits .

 
ORIGINAL: jemstone29@hotmail.c



Now my question is , does the slow speed fan resistor ( if failed) stop the fans from working at high speed,?


Jeremy
Click to expand...

the simple answer is no. The high speed fan supply is fed seperately via the fan relay when the ignition is switched on.

With the ignition off the fan supply should come from the battery to the fuse then directly to the resistor then to the fan motor .
You should see some voltage at the fuse ?
If yes then you should see voltage at the motor ?
If you have voltage at the motor then try running a lead from the earth side of the motor to chassis earth . This should bypass your rad temperature switch and force the fan motor to run. ?
BE CAREFULL make sure you only earth the earth side of the fan motor obviously !

if it still doesn't run then your fan is fubar !

If you remove the electrical connector to the radiator temperature sensor switch and bypass the switch by bridging the terminals on the wiring connector the fan should run both ignition off and ignition on
 
Cheers All, very useful info as always :)

I'm awaiting the delivery of a 'fleabay' fan (hope it is as stated on the tin!) and will fit this weekend coming and let you know

As always appreciate the assisatance

Jeremy
 

ORIGINAL: pauljmcnulty

What've you done with your "peanut" account, Nick? [8|]
Click to expand...


danged if I know Paul ?[;)] this happened once before a few months ago and you very kindly sorted my original log in for me.
One day last week I couldn't log in and I couldn't contact anyone on the site . I managed to find this tempoary login ID I made the last time this happened.

 
HI, just to close off the query for anybody that searches in times to come, it was the fan that was knackered. Very stiff almost seized. I squirted a load of GT 80 / WD40 into the fan motor casing and left it over night with some interim turning by hand and it now works a treat !! I've also got a spare fan incase it is of limited life span. Only problem now is the slight dodgy spade connection to the radiator switch that occassionally makes the fan not come on.

Thanks all for the help

[:)]
 
thats good news , well done for salvaging the fan . I love conservation [:D]

Good to be able to close issues on threads for future searchers..... thanks
 
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