Electic fan control,-6$

The relay is a SPDT (single poll, double throw). The harness colors are for a 97+, I'm nit sure about pre-97's. You can get the relay at just about any radioshack for 6$. Make sure its rated at 40A. A simple on/off switch can be used insted of the more expensive LED one, it just wont have the ground. Any way, I had the switch laying around and who dosent have some wire, so It cost me the price of the relay- 6$... lot better than 36$+shipping. Sure It's easier to just buy it, but hey, I'ma do myself kinda guy- good luck
-Oh, yeah, when the switch is off, it still functions normally!!:yelclap:
http://www.villagephotos.com/viewpubimage.asp?id_=9924456&selected=1006899
-lemme know if this helps out at all

Im not ellectically inclined, so I don't know what every thing means. Like the box with the squiggly lines and the round thing. It is a great diagram, but people like me need some explaining- little help please!

-Ok, the BIG round thing is the switch. It has +12V in (red), +12V out (orange) and a ground (enables LED to light up, Black).-Square thing is the relay, you dont need to know what it does, just make sure you hook it up right. But, if you want to know, the squigly thing is a coil. When the coil is charged (When switch is "on") =12V flows through it. This basically turns it into an electromagnet that pulls the contacts between #87 and #30 together. Thus, sending +12V from the battery to the fan, bypassing all the other things that control the fan (temp, defroster, A/C).
- When the switch is off, the coil is not charged, thus contacts #30 and #87A are connected- returning the fan to "normal mode"
- as for the #86 and #85 connections- dont worry about which one sees
+12V and which one gets grounded, it will work either way.
- Hope that helps some- Some relays you can get with a harness that makes attachments a lot easier

Well.. am I helping anybody out here that has wanted to try this?- its not hard, lemme know if you have any q's

ive been drawing up ways to do this, thanks man this helps a ton
just a few Qs....do you NEED a spdt, or can i just use a rocker switch (like for my hellas), or is it the same thing? i cant remember if im thinking of dpdt or spdt switches. reason i ask is i have a switch panel in my xj for lights and fans, and i have one left over that i could use.
other than that, this looks awesome. great weekend project when i get back from wheelin this weekend
-Bennett

Great diagram.

I think I understand what you are doing.

Just to clarify, you are leaving the green wire alone.
You spliced the blue wire, which is the hot/power wire/12v supply.
In normal operation the power flows through 87A and 30, and to the fan.
When you flip the switch, you energize the coil, which pulls the contact for power flow from 87A to 87. Now you power is flowing through 87 and 30, and to the fan.

As for wire size, you would use a heavy gauge primary wire for the battery connection to the relay.
The low current wire and the relay to switch connection do not have to be as large, correct? What size would you recommend?

Thank you

I'm not familiar with Hella wireing- however, - the purpose for having the relay is so that it can be mounted away from the switch so that the heavier gauge wiring ( the ones going to the fan) does not have to be run into the cab. I used 14 ga. to run to my switch- plenty to handel the small amount of current that it takes to activate the coil.
-as for the spdt- Yes I'd say your better off with that- first it will be a lot simpler to wire and second- If you didnt use it, multiple relays would more than likely be needed.
- I prefered to do it this way rather than some other sites that messed around with the stock fan relay- I didnt like the thought of screwing up that and having no fan at all
- again I'm not familiar with the Hellas so I dont really know-

XJ4PLAY said:

Great diagram.

I think I understand what you are doing.

Just to clarify, you are leaving the green wire alone.
You spliced the blue wire, which is the hot/power wire/12v supply.
In normal operation the power flows through 87A and 30, and to the fan.
When you flip the switch, you energize the coil, which pulls the contact for power flow from 87A to 87. Now you power is flowing through 87 and 30, and to the fan.

As for wire size, you would use a heavy gauge primary wire for the battery connection to the relay.
The low current wire and the relay to switch connection do not have to be as large, correct? What size would you recommend?

Thank you

Click to expand...

-Bingo- you got it... I ran 14Ga. using a +12V lead off the fuse box

dothedew24_7 said:

-Bingo- you got it... I ran 14Ga. using a +12V lead off the fuse box

Click to expand...

Do you mean the fuse box in the cabin or the one in the engine bay?
I am assuming the one in the cabin. Did you piggy back on something or find an unused power source?

XJ4PLAY said:

Do you mean the fuse box in the cabin or the one in the engine bay?
I am assuming the one in the cabin. Did you piggy back on something or find an unused power source?

Click to expand...

Well, it would be the one in the cabin, you could run it off of somthing else, just make sure its +12V when the ignition is off- If you want to run fan with key out of ignition-
- I made my own "Fuse box" its located under the center console- my reason for this is b/c my original kickpanel fuse box is inacesible now, so I ran a 8 Ga power and ground wires from the batt to under my console, things that are fused are fused, in this case the switch is not- and really doesnt need to be-
obviously you dont need to do all that jusy hijack a constant 12+ in the fuse box- Or i guess you could splice into a variety of other sources within the cab