This should help you.

 

Thanks, but the only thing I think I understand from this schematic is that 87A is not used, pin 30 is for power from the battery/ignition switch, and 87 goes to the fan. I still don't understand what I need to do with pin 85 and 86.

 

I understand what you need
Ignore the diode if your relay does not have one
I made a mistake on bypass switch use 2nd drawing

 

I understand what you need
Ignore the diode if your relay does not have one

This schematic makes more sense to me. I just won't be using pin 30 on the relay as the only power currently going to my fan is coming from the ignition switch.


So I will by wiring it as follow:


85 to ignition switch
87 to fan
86 to thermostat
30 ignored?


Thanks!

 

Not quite
85 is COIL POSITIVE (hooks to ignition positive)
86 is COIL TRIGGER (hooks to your fan thermostat negative)
87 is LOAD (goes to fan positive)
30 is POWER (goes to battery)
87a is NOT USED

Basically; the ignition sets the relay coil in the ready mode, the thermostat turns the relay on by suppling ground, which closes the relay connecting the relay's contacts #30 & #87 together engaging the fan.

 

Not quite
85 is COIL POSITIVE (hooks to ignition positive)
86 is COIL TRIGGER (hooks to your fan thermostat negative)
87 is LOAD (goes to fan positive)
30 is POWER (goes to battery)
87a is NOT USED

Basically; the ignition sets the relay coil in the ready mode, the thermostat turns the relay on by suppling ground, which closes the relay connecting the relay's contacts #30 & #87 together engaging the fan.

Just wire it like this, or give it up. Only way it makes sense.

Make sure that wire to term 30 and wire from term 87 can handle the max current for your fan. Make sure the wire to term 30 is fused at the starter. If you want 30A service from the starter to your fan (and from fan to ground), use 10 gauge wire and a 30A fuse in-line. Solder everything (no non-professional type crimp connectors).

 

Summit fan control kit
https://www.summitracing.com/parts/sum-890115

Instructions for the kit with a Bosch relay
https://static.atechmotorsports.com/global/images/instructions/sum-890115.pdf

these make life easy, comes with a hi-cap circuit breaker, wiring with molded plug

 

It is better to connect the fan relay #30 to the battery through a fuse rather than through the ignition. Some fans draw more power than the ignition circuit can supply. Wiring the relay to the battery eliminates this and supplies the power the fan requires without effecting ignition. Provided proper wire sizing to current load is used along with fuses or other circuit protection.

 

Only problem I see is that the way my fan is currently wired is through the ignition switch (I don't think there's a wire coming from the battery to the fan) and my battery is in the trunk. The fan only turns on if the ignition key is in the on position. I'm assuming that if I run a wire from the battery to pin #30 the fan will turn on when up to temp even with the ignition key off.

 

If you wire that way there is no need for the relay, it will only be a secondary switch and have no benefit.
The purpose of the relay is to take the load off of the ignition circuit by sourcing its current directly from the battery. If the wire from your battery in the trunk going to the starter is properly sized you can source the fans power from the starter.

 

Thanks for the clarification. The main reason for me to install this relay is because the fan is causing the engine to run off (as if dieseling) for about 2-3 seconds after the ignition switch is turned off. But I guess while I'm at it I might as well wire the relay properly by wiring #30 to the battery.

 

If you wire the relay #30 to the battery you'll stop the after run caused by the fans induced voltage.
If you wire the relay #30 to the ignition you will continue to have after run from the fan because the fans induced voltage will hold the relay closed and keep the ignition energized.

 

Easy to figure out here: https://watsons-streetworks.com/a-current-topic/

 

Usually the thermostat does not have a positive, it simply switches to ground. If it is wired to your fans negative this would indicate it is operating as a ground switch.

Remove thermostat wire from the fan negative and connect the thermostat wire to the relay's #86 terminal. Connect the fan's negative wire to ground.

 

I'm sorry but I'm getting a bit confused. This is an adjustable temperature thermostat and it has 2 wires, one goes to ground and the other goes to the fan's negative. Are you saying I should remove the one wire that connects with the fan's negative and connect that to the the relay's #86? What should I do with the thermostat's negative cable then? Thanks

 

Glad it worked out, what you have is the same setup I have.

Every relay I've ever seen had smaller prongs for the control, and bigger prongs for the load. And this should show on the socket(if equipped) the relay plugs into, by having 2 wires bigger than the other 2 wires.

As for your voltage drop, you're coming straight off the battery vs a switched 12v source with who knows how many other things on it.