Thread: Thermos, A/c and temp senders....

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You will need to determine the hot wire to turn on the a/c and use that to trigger the fan to come on using the relay.....

The relay for the fan itself can use the same power wire as the other 2 relays.

The manual overide relay and all the others should be located close together as to minimize the wire distance and resistance.

Basically a hot wire of the proper guage to the first relay and then another short power wire of the same guage to the next one and then to the next one as the relays have power at all times, they only complete the circut when the switch wire gives the signal.
Each relay will need a seperate trigger/switch wire...one coming from the manual overide to one relay, one from the thermostat and one from the a/c compressor......

A good volt meter should help you find which wire is energized to the compressor when turned on.Use this wire to the switched connection on your relay.

Make shure to ground everything good also...A little dielectric grease goes a long way to help with all connections and prevent corosion too.

Hopefully this helps a little......

This should allow the fan to stay off untill the thermostat tells it to run or the manual switch is flipped or the compressor comes on.......usually the fan runs continuously when the a/c is on in most applications to help cool the a/c refridgerent temps rather than cool the radiator of the engine...this helps to keep the a/c cool inside during idle and low speeds.

I would also calculate the fans total amps and use a inline fuse on the hot wire powering all the relays..........or use the wire size you determine and use the appropiate fuse size...preferably a blade fuse...they make some nice ones with rubber around them and a little flap to sort of seal the fuse from weather.....I used a 50 amp one from a stereo shop and some pretty heavy wire for a high end stereo set up.

Also you can use the same outputs of the relays to power the fan..connect the main power feed from the fan to one of the relays and jumper the relays outputs from one to another.......this will allow the system to work automatically........I would not recomend having a main switch to activate all of these relays...........if you forget to turn the main overheating and engine death are likely.

The way I have described will allow all of the systems to work in unison and this is the recomended way..........In my opinion having a main on button to activate all of these systems is a race only deal....have heard many people forget to turn on fan power when it has a main to activate it....too many distractions on a street car to remember to turn the fan on everytime....sooner or later it will get forgotten...