Originally posted by john6066:
thanks guys. a lot to digest. sounds like relays are the way to go. i installed a cooling fan and did not use a relay. opps i'll get on it.
When you change your electric fan to run with relays, you should notice an increase in fan speed due to less voltage drop.
Keep the high current wiring as short as possible and use a heavy guage wiring like 8 or 10 gauge, depending on what your fan draws to keep voltage drop to a minimum and fan speed high.
Some of the better fans require more then a 30 amp relay. The high speed of a taurus fan or a Mark VIII fan require a bigger relay then 30 amps.
Also a free wheeling diode wired accross the fan's electrical terminals, but between the fan and relay will help your relays live a longer life.
Some HD relays for motor circuits allready have the free wheeling diodes installed in them at the factory e.g. Bosch 75 amp motor relay.