I want to install a manual fan switch, however someone gave me a diagram to do it with a relay and that way when you have the switch off the fan still works when it hits 220. Ive never used relays before...are they hard to work with and how do you use them? Somebody please explain to me like im a child...thanks.

 

I don't claim to be an expert, but I will try to explain. You have 5 pins on the relay, some have four. A constant 12 volts goes to one side, the wire to your fan would go to the side of the relay. When you flip the switch on, you send 12 volts to the third pin of the relay. this closes the relay, allowing 12 volts to go to your fan. This way, you can run a higher amperage through the relay instead of the switch. Have you ever seen a 30 or 40 amp automotive switch? They are huge. Anyone feel free to correct me on my explanation. Like I said, I may be wrong.

 

Josh,
If you have a computer controlled 91RS, then you already have a fan relay from the factory that is triggered via a ground signal from your ECM. This is very easy to override with a simple toggle & no other relays. Simply ground one side of your toggle switch and run the other side of the toggle to the relay. You would splice in your ground from the toggle to the small (green & white) wire going into your fan relay. This will allow normal computer control all the time, plus you can activate the fan via the toggle whenever you want.

The purpose of a relay is to switch battery power to a high-current accessory such as a fan. The relay will need another (smaller) switch to activate it.

A 5-prong relay (SPDT = single pole dual throw) has five labelled connections on it based on a standard. Two of the connections are a power & ground that are required to activate the internal relay contacts.
#86 = 12v+ (battery or ignition)
#85 = 12v- (ground)

The remaining three prongs connect to your high-current source and accessory. The source or accessory can hook to any of these three contacts depending on how you want your switching to work. You can use a SPDT-relay for either activation or as a kill switch to a high-current accessory.

For activation, you connect your high-current source (battery) to the #30 terminal on the relay. Your accessory (fan) will get it's switched power from the #87 terminal. The fifth terminal #87a would not be used in this case and should be taped off to protect from shorts.
In this configuration, you can use either a ground or 12v+ to trigger the relay (via #85 or #86) to make contact. Once the relay is triggered it will internally connect the #30 and #87 terminals to supply power to your accessory.

To use the relay as a kill switch, you would connect your accessory to the #87a terminal so that it is normally always energized. Then when the relay is triggered the connection will switch to the #87 terminal and kill the accessory.
An alternate way to wire a kill is to connect your accessory to the #30 terminal and your power source to the #87a terminal. You can also swap power sources or accessories with a SPDT relay.

you can go here on the web for pictures and more explaination.

http://www.the12volt.com/relays/relays.asp

 

So if i just splic into the ground wire with a switch...the fan will still come on at the stock temperature settings even if i have the switch "off"? If that will work thats great... i guess i was under the understanding that once you broke the ground wire with the switch, it would ONLY work from that switch, and not at stock temp turn on.

 

Yes,

you do not break the green/white wire.
you simply splice in with your own (switch activated) ground.

the ECM will still ground the green/white wire when it wants to.

 

OH OK I SEE NOW!! Cool...thats so much easier then wiring in a relay. Ok well im about to go do that now then. Thanks for the info.