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  #1  
Old 09-04-2009
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What wire do I tap into?

I want to have my A/C power an efan relay, what wire do I tap into on my 05 3.0? I know I have to wire in a diode, but does the silver band go towards the relay or clutch? I think it goes towards relay, but not sure.

Relay -----|<---- A/C clutch.................right?
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Old 09-05-2009
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I think it is a purple cable that plugs into the air conditioning pump. wouldn't make sense to tap into a wire behind the dash to run your relays when the wires are already in the engine bay.

I know I looked into it and have a thread on it. I never did it, but had it all planned out.
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Old 09-05-2009
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I dont have an 05 schematic but, if the AC control switch works similar to an 01 (sends power signal to PCM) you could tap it to send a positive signal to the relay coil. However, youd need to install an anti-spiking diode between relay terminals 85 and 86 and an isolating diode inline between the switch tap and the relay as shown in pic 1.

Name:  FanRelay.jpg
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You can also tap the A/C Clutch power feed to control the relay. However, if the clutch does not have a built in anti-spiking diode Id strongly recommend installing one at the plug as shown in pc 2.

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Make sure the relay and fuse are rated to handle the current the fan will draw plus 10%.

Recommend using 1N4005 diodes for relay and 1N5399 at A/C clutch plug. You can pick them up from Radio Shack.
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Old 09-07-2009
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Quote:
Originally Posted by Rev View Post
I dont have an 05 schematic but, if the AC control switch works similar to an 01 (sends power signal to PCM) you could tap it to send a positive signal to the relay coil. However, youd need to install an anti-spiking diode between relay terminals 85 and 86 and an isolating diode inline between the switch tap and the relay as shown in pic 1.

[IMG]http://i224.photobucket.com/albums/dd303/revinsd/FanRelay.jpg[IMG]


You can also tap the A/C Clutch power feed to control the relay. However, if the clutch does not have a built in anti-spiking diode Id strongly recommend installing one at the plug as shown in pc 2.

[IMG]http://i224.photobucket.com/albums/dd303/revinsd/FanRelay2.jpg[IMG]


Make sure the relay and fuse are rated to handle the current the fan will draw plus 10%.

Recommend using 1N4005 diodes for relay and 1N5399 at A/C clutch plug. You can pick them up from Radio Shack.
Thanks for the input, Ive got 75A relays and theyve been working great so far. Right now Ive got it setup with a 3 position switch, HI-OFF-AUTO. Auto powers up a temperature switch (207on - 202off) which activates the LO speed relay. I had planned to have the AC wire power up the LO relay. Ive got a 1N4005 wired in between the clutch wire and relay I plan on using.
Ive also got a "free spinning diode" going from the LO power wire off the fan to a ground, is that what you mean by anti-spiking diode? I'll draw up my schematic so you know how Im running my fans.
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Old 09-07-2009
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This is hi=ow Im running my fan right now...red stuff is what I had planned on doing.

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Old 09-07-2009
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When power to the AC clutch is cut a secondary voltage is induced in the coil that can spike upwards of 400-500 volts. You may want to install the anti-spiking diode between the power and ground wire at the AC compressor plug.

Name:  FanRelay3.jpg
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Old 09-07-2009
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A 1N5407 should do right? That's what I've got on the LO lead...I've got an extra one and could wire it in where you suggest.
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Old 09-08-2009
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BTW, I only have these two wires, gray and black. Am I looking in the right spot? I figured the compressor would be the best place.

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Old 09-08-2009
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This is what I came up with, but couldn't figure out what diodes to use or size of capacitors to use. Capacitors are optional, but are supposed to prolong the life of the relays. A small relay could be used instead of the transistor.
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Old 09-08-2009
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Looks like a good setup, I just wanted to have my relays independent of each other. That way, if say the LO relay fails, I can still power up the HI side. I didnt draw them there, but I have LEDs hooked up to the wires powering up the fan, just to make sure I know when the fan is getting power. Thanks for sharing though, maybe now you can use the diodes Im using/will use.
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Old 09-08-2009
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what temp switch were you going to use and how were you going to use it.

what happens if you aren't in the driver's seat and it starts to overheat? I'd want some way for the controlling logic to go to high speed for me.
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Old 09-08-2009
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Quote:
Originally Posted by ccernst View Post
what temp switch were you going to use and how were you going to use it.

what happens if you aren't in the driver's seat and it starts to overheat? I'd want some way for the controlling logic to go to high speed for me.

Im using a 210 on - 200 off temp switch from indexsensors.com. I think you edited your post before I got here, but the switch will power the relay once it reaches 210 and will cut power once it goes back down to 200.

I dont know why the truck would be on if Im not inside, but my toggle switch is always on the LO/AUTO position where the fan will come on at that time. Ive been in 105F heat, idling and A/C on full blast and the fan was able to cool it down to 200, no problem. Ive yet to use HI If Im driving and notice temps are not coming down, I can flip it to HI, control the temp and then switch back to auto.
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Old 09-08-2009
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Quote:
Originally Posted by eddiefromcali View Post
BTW, I only have these two wires, gray and black. Am I looking in the right spot? I figured the compressor would be the best place.
The 1N5407 should work other than its physical size is a little large. Yes you want to install it between the GY/WH and BK wire (band towards the GY/WH) just above the plug and insulate it as needed (recommend soldering). If your cluster has a high temp idiot light you could tie into its circuit using a transistor to trip the high speed relay just in case.
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Old 09-08-2009
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Quote:
Originally Posted by Rev View Post
The 1N5407 should work other than its physical size is a little large. Yes you want to install it between the GY/WH and BK wire (band towards the GY/WH) just above the plug and insulate it as needed (recommend soldering). If your cluster has a high temp idiot light you could tie into its circuit using a transistor to trip the high speed relay just in case.
never though of the idiot light circuit...good idea...thanks for all your help! Most efan write ups are very basic or rely on a fan controller, I dont like those things and would rather make my own setup to work how I want it to. Thanks again!
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Old 09-08-2009
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if you use the idiot light to trip the 2nd relay, wouldn't also want to "un-trip" the first one so you aren't sending power to both the high and low power cables on the fan?
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Old 09-08-2009
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You can, by wiring the relays in series....kinda like your setup
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Old 09-08-2009
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right, but then if you lose a relay, then you are done...you'd need another set of relays in parallel for redundancy.
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Old 09-08-2009
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yup, thats why I dont have them wired that way. I think that both leads from the fan are powered once on HI though. The reason I say this is because when I wired up my LEDs, I did the LO one first and the light comes on on LO & HI. IDK if powering both leads would kill the motor faster or not, but thats what Ive noticed.
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Old 09-08-2009
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I think the best bet here would be to find a sensor with two settings. I saw a post on a forum of a guy who used an OEM switch with two settings. If I remember correctly, the temps where too low imo, but they do exist and something like that could be used.
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Old 09-08-2009
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Just realized that the company I used for my sensor also makes dual setting temp switches http://www.indexsensors.com/pdfs/el_temp_cp.pdf
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