my thermo fans seem to have a mind of there own! sometimes they work as they should and other times they only seem to work at half speed, even with A/C on full,when this happens the temp gets very hot.
i have replaced the radiator and thermostat and the fans themselves with brand new units! yet still the same!
when i remove the coolant temp sensor plug they come on full speed when the engine is running of course.
could i have a flakey relay somewhere?
i am all out of ideas please Help!!

The relays should have been the first thing to look at.

They're located behind the passenger headlight.
4 in total.

Possibly 3 with V8's