Cooling fan

[rolemin]

I need some help again.My cooling fan on a 1986 4gtl does not seem to work via temperature sender unit.If I bypass it it does run I replaced sender unit but still no joy.can anybody tell me what else may cause this to happen.thanks in advance

 

[iMacThere4iAm]

I think the temperature switch is available in two versions, with different cut-in temperatures. Have you got the right one?

Maybe try immersing it in boiling water, to see if the switch closes.

 

[rolemin]

I did wonder if there were different temp tolerances maybe that is worth a try .......Thanks

 

[rolemin]

Are you thinking I mean thermostat?

 

[Azazello]

Are you sure the thermostatic valve is working properly? If hot water does not go into the rad, the fan will not start...
Elsewere I will check for masses and cable interruptions.

 

[rolemin]

Yeah all hoses get hot and heater works

 

[iMacThere4iAm]

Are you thinking I mean thermostat?

No, I did mean the switch. But Azazello makes a good point about the thermostat. Edit: you posted while I was typing!

For testing the switch you might try connecting it to a multimeter or a battery and bulb while you boil it (!)

 

[rolemin]

Ok thanks will try those ideas next day or so

 

[mr-reno-139]

When you mention bypass switch are you fitting a link wire between the push on terminal or connecting motor direct to battery ?
Worth cutting off the old terminals and crimping new ones for good connection to switch
how hot does car get maybe it is not getting to 85c at bottom of radiator possible you are not waiting long enough or does it start to boil if you leave it idling for 15 to 20 minutes?
I have got a infrared hand held thermometer gun which can check tempura ture across whole rad is to as it is possible for radiator to be blocked at the bottom with sediment
This can be used as well as checking for correct operation of thermostat in hose
If you can touch the brass part of switch and keep finger on it it has not got to 85c lol
Last thought if it has got early stage head gasket problem it is likely to bubble in bottle well before fan is due to cut in
Hope this helps

 

[rolemin]

Thanks will look at your suggestions.I was taking connections off sender unit and putting a wire between them and when turn key fan would start

 

[David M]

Another possibility is that the bottom of your radiator s blocked with scale. As the radiator tubes are horizontal, they are easily affected by the buildup.
It could affect the coolant flow to the right hand side of the radiator where the switch is located

 

[mr-reno-139]

Think I covered that possibility in my reply but it is always good to have a 2nd opinion
Especially one that is the same as mine ☺

 

[rolemin]

Gave rad a bit of a flush out although doesn't look like been on car silly amount of time then changed sender unit and hey presto after 10/15 mins on tick over fan came to life

 

[mr-reno-139]

Well done I am sure some third and fourth opinions would have agreed too ☺