Best way to wire in electric fans?

[mebe007]

ok guys i have a derale thermostat (adjustable) w/ built in relay etc. its what the guys at derale recomended to me for wiring in my dual fans. anyways im worried they might draw to many amp possible although i was told they were within spec of the relay. but i have 2 relays i can wire in if i have to. So what would you recommend the best way to wire up the system? i notice the derale instructions call for using the ground as the switch. also i will use a switch on the ac circuit as the overide/backup.

heres the instructions
http://static.summitracing.com/global/i ... -16749.pdf

 

[Longroof79]

Mark,
I would use a relay per fan. Dual fan= two relays. Is the Derale unit a fan controller where you can manually adjust the temps where the fan kicks on and off?
I plan to use two relays for my dual fans. I also think it's the recommended method. An override switch is also a good idea.

Ooops! I spoke too soon before checking out the instruction link.

 

[mebe007]

http://www.summitracing.com/parts/DER-16749/
thats the unit i have. it is an adjustable thermostat/ fan controller. It read the instructions and it can work for dual fans but combined amp draw cannot exceed 25 amps. it utilizes a ground switching circuit.

what i am trying to do or figure out i guess it to use that module to control 2 relays 1 per fan. I know 30 is constant, 85 should be ground, 86 is switched, and 87 is output.

so from what im getting from the fan controller instructions it uses the fused ground as a switch with a positive lead directly from the battery for the fan power. so i could run a relay for each fan with constant fused power coming from the battery to 37 and then the output 87 would go to each fan. what confuses me is how to use the switched ground wire from the controller in the relay to make it work. would i put chassis ground to 85 and the switched to 86. im confused because of the switched ground and not power.

 

[pontiacgp]

nice thing about relays is that they can only help and not cause any problems even if not needed...85 ground, 87 power out to fan, 86 trigger(power from master relay) and 30 - 12 volt source

 

[mebe007]

im wondering if i should get a different controller, something like this: http://www.summitracing.com/parts/DER-16789/ or a simple fixed switch like 185 on 170 off. running a 180 tstat in the motor

 

[mebe007]

so this is whats on my mind as a possible way to install the relays with the current switch. fused batt power in terminal 30, power out to fan on terminal 87, terminal 86 can just run a jumper off terminal 30 and then use the switched ground from the controller to terminal 86. i believe this would make everything work the proper way.

i believe what this will essentially do is: the fans will have dedicated ground and relayed power each from separate relays which are switched via the fan controller/relayed ground switch. so essentially there is now way the switch/controller would see the amp draw of the fans.

Someone please correct me if i am wrong here or please add any extra input you see fit. if this controller wont work for what i want i can always sell it and get another.

 

[FE3X CLONE]

Something to keep in mind but you my want to look at using normally closed relay's. This way you can wire it up so that if the controller or relays fail they fail in a position that would keep the fans running.

Yes, they would run continuous no matter what in this situation but its better than being in the middle of nowhere and the car overheating.

 

[mebe007]

Something to keep in mind but you my want to look at using normally closed relay's. This way you can wire it up so that if the controller or relays fail they fail in a position that would keep the fans running.

Yes, they would run continuous no matter what in this situation but its better than being in the middle of nowhere and the car overheating.

very true or i could keep a couple spares in the glove box lol. will the way i mentioned wiring it work? makes sense in my head.

 

[foxtrot]

I would rather have the normally open relay. My reasoning is if the controller fails that the fans won't stay on. As long as the car is moving, it won't overheat. Mechanical fan is better for an old school ride anyways. Just my two cents.

 

[mebe007]

I would rather have the normally open relay. My reasoning is if the controller fails that the fans won't stay on. As long as the car is moving, it won't overheat. Mechanical fan is better for an old school ride anyways. Just my two cents.

right well this is old school/ new school, i have the fans, custom shroud and controller already so they are here to stay lol.