thermo fan

[yorkie]

g'day all, first post so be nice!

i have a toyota surf 2.4td which has a problem with the thermo fan. everytime the key is turned the fan comes on, i have replace the sensor with the hilux 2.8/2.4 part but still the fan runs.
what would be the best way to check for a short/fault.
the way i see it the fan always has 12v to it, when the sensor engages the power source is earthed and the fan comes on. i checked the relay and it seems to work ok, two pins of the four are receiving power and the other two are nil voltage.
appreciate if anyone can give some suggestions as to what is going on, prior to it coming on all the time the fan would come on intermitantly and the previous sensor was corroded.

thanks
yorkie.

[bazzle]

remove wires off sensor. Put an ohm or continuity meter across sensor. Should be open circuit (no continuity) as engine reaches op temp it should give continuity.
May be easier to remove and put bottom part in cold water and bring to boil whilst checking for op.

Also check relay doesnt have contacts perm om.

Bazzle

[murcod]

Start by just pulling the wire off the sensor and see if that stops the fan. If it does you've still got sensor problems, if it doesn't then the problem is most likely in the wiring or the relay.

Try swapping the relay over after that to narrow it down further.

[yorkie]

g'day guys,

well it seems the wiring to the relay is at fault, with ignition off only one pin has power to it, turn the key and a second pin gets power and the fan starts. sometimes tho if you turn the key the fan does not start and checking the relay only one pin has power. i'm starting to think there is a bad connection/short somewhere as the problem is intermittent.

thanks
yorkie.