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  #166  
Old April 8th, 2014, 18:38
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kastein kastein is offline
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Re: Radiator Fan Override Switch (The Easy Way)

ummm... that does not sound like the right solution at all to me. But if it works, it works.

I would really suggest a resistor to 12V rather than tapping into a second output. It's not going to burn anything out since they're both ground-side-switched outputs, but you may get a code when the ECU attempts to turn the fan on without the air conditioning also being active, I'm not sure.
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  #167  
Old April 8th, 2014, 18:47
jodybbad jodybbad is offline
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Re: Radiator Fan Override Switch (The Easy Way)

I was thinking the same thing about the the high temp e-fan trying to kick on. Maybe it won't get that hot. If it does I might have to back up and punt if it throws a fault. But I also thought it may be a good thing if the check engine light comes on when it gets hot enough for an e-fan signal. That would be a good reminder to pull over and see why its so hot.
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  #168  
Old April 8th, 2014, 19:10
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kastein kastein is offline
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Re: Radiator Fan Override Switch (The Easy Way)

You could also just do it the right way with a resistor... but hey, it's your jeep. Do hinky strange things to it all day if you want.
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  #169  
Old April 8th, 2014, 19:25
jodybbad jodybbad is offline
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Re: Radiator Fan Override Switch (The Easy Way)

you are probably right and i probably will if it becomes a problem.. Hinky strange things arent always bad unless goats are involved
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  #170  
Old April 10th, 2014, 19:20
jodybbad jodybbad is offline
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Re: Radiator Fan Override Switch (The Easy Way)

The a/c pump must cut off under hard acceleration or for some other reason when the electric fan is still running and the engine is cool. So i put the 1/8 watt 470 ohm resistor in and its happy trails. shoulda done it the first time.. i know .. but things stick with me better when I learn the hard way. thanks mark for the advice..
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  #171  
Old May 24th, 2014, 07:15
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Re: Radiator Fan Override Switch (The Easy Way)

okay i understand the wiring diagram the only thing im confused on is the switch. Now is the switch just grounding out the 87 terminal? 87 runs to fan but in the middle of 87 is basically a 3 way and runs to switch, and when switch is on it provides the ground? is this right?
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  #172  
Old May 24th, 2014, 18:47
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Re: Radiator Fan Override Switch (The Easy Way)

Anyone out there? lol just looking for a little bit of advice on the subject so I can finish the install. Thanks again
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  #173  
Old May 26th, 2014, 22:36
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

I'm a little confused by how you worded your question. Yes, the switch is providing a ground to activate the coil in the factory relay. While it is connected to the new relay, it has no effect on the new relay.

If you're referring however to the second wiring diagram which demonstrates the use of a 3-way switch to provide an "off" position... then the switch is either grounding the factory relay, allowing the new relay to ground the factory relay, or breaking the ground connection altogether to keep the factory relay from activating. Does this answer your question?
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  #174  
Old May 27th, 2014, 07:43
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Re: Radiator Fan Override Switch (The Easy Way)

Sorry about that I'm just confused myself. Basically I'm wondering 1) where do I connect the wire for the switch at the relay 2) where on a normal illuminated rocker switch with 3 prongs (ground, 12v, accessories) do I plug in the wire from relay. I understand how to install the relay just not how to hook up the switch to it. From the dia grams it looks like I just attach it any where on the wire to turminal 87? And the switch is only on and off but is illuminated thanks for the help
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  #175  
Old May 28th, 2014, 11:09
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

You can connect the wire between the switch and the relay anywhere that is convenient, electrically speaking, it's all the same. I crimped it together with the extended DB/PK wire on the 87 terminal of the new relay as seen in the 4th picture in my original post.

With a lighted switch being used to ground a circuit, you have to switch some things around. But first, is it always illuminated, or is it an indicator light that turns on when the switch is activated? And second, is it an LED or an incandescent bulb?
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  #176  
Old May 28th, 2014, 13:02
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Re: Radiator Fan Override Switch (The Easy Way)

its a regular incandescent bulb switch. I played around with it and finally figured it out. I spliced it into the 87 termanel wire and changed the wires around at the switch until it worked. its hooked to the power and the ground. the accessories termanal is not used. if you hook it up the the acc termanl the fan automatically run with the switch on or off. Its all together now just need to perminatly mount the switch. Thanks for the help Fyrfytr
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  #177  
Old May 28th, 2014, 17:15
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Glad you got it figured out. Sounds like you went about it a different way, but if it works, it works.

Typically (since the switch is providing a ground) you would hook the switch up somewhat backwards... a ground to the 12V terminal, an ignition switched 12V source to the ground terminal, and the wire leading to 87 on the new relay to the ACC terminal. The reason I asked about it being an LED is that they won't work in this configuration as LEDs are directional.
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  #178  
Old July 2nd, 2014, 15:22
beasticles beasticles is offline
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Re: Radiator Fan Override Switch (The Easy Way)

fyrfytr - Let me just start by saying I really appreciate all of the help you have given us late model XJ guys by figuring out how to run the aux fan override without throwing a CEL. I think the design change Jeep made for 2000 and 2001 XJ models to do away with the AC on triggered aux fan, and stick solely to a computer based reading of AC system charge or engine temp was dumb. I have redone the following in my 2000 XJ myself: new radiator single core, coolant system flush with 50/50 Zerex G05 - distilled water mix, new e-fan, and still with the AC on in traffic on a hot day it is constantly hitting the 217* limiter that kicks on the aux fan on. When rolling in stop and go traffic on a hot day, I would rather just be able to kick the aux fan on manually until I am off and moving again. This likely would also help the AC stay cooler - on 95* days my AC just can't get cold, more like a mildly cold breeze.

That leads me to my questions about your diagram. I am shade tree mechanic and my electrical expertise is limited. Can you take a look at my below updates to your chart and let me know if I have labeled everything correctly, particularly the new relay numbers? Really appreciate the help.

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  #179  
Old July 4th, 2014, 21:24
fyrfytr1717 fyrfytr1717 is offline
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Re: Radiator Fan Override Switch (The Easy Way)

Close but not quite:

1. Your "New Relay" numbers are correct.

2. The ST-RUN source in your green box is NOT the battery. It is a fused 12V+ source that is only hot when the key is in the Start or Run position. I detail where to find this DB/WT wire in the original post. It can be found elsewhere, that was just a convenient location for my relay placement.

3. See #2 regarding your dark blue box. You are using a fused 12V+ source so an in-line fuse is not necessary. If putting one in would make you feel better, you could probably use the smallest one you could find. A relay coil uses almost no amperage. Not necessary though.

4. Engine compartment ground in your light blue box goes anywhere that is convenient. Lots of options to choose from, I think I used a ring terminal on an existing grounding screw near the air box. You could also tap an existing ground wire somewhere in the harness, or you could even ground to the battery if you really wanted.

5. If you mount the override switch in the cabin and the new relay is in the engine compartment, then yes, the ground wire passes through the firewall as indicated in your red box. There's a spot in the driver's footwell that I like to use.

6. Grounding inside the cabin has lots of options as well. Again you could find an existing grounding screw and use a ring terminal. I tapped a ground wire in the overhead console as that's where my switch is mounted. There are also ground wires to be tapped in the center console and the dash depending on where you mount your switch. Dash lighting circuits are usually pretty easy to find and safe to tap into for this use.
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  #180  
Old July 8th, 2014, 09:10
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Re: Radiator Fan Override Switch (The Easy Way)

fyrfyt: first of all thanks a ton for this writeup. I've been studying it and learning a lot. Last night I put my relay in (NAPA Bosch-type 5 pin) and simple toggle to my dash. I haven't tested to see if the PCM will turn on the fan at 218 with the switch OFF yet, but the fan does not come on automatically when my A/C is flipped on. (1998 XJ) I've been studying more to figure out where I went wrong.

In your writeup, this is the pinout specified for the relay:

Quote:
Relay Pin 85 - DB/PK wire coming from your PCM
Relay Pin 86 - DB/WT (ST-RUN) wire
Relay Pin 30 - Ground wire
Relay Pin 87 - DB/PK wire going to the Fan Motor Relay (in the PDC) and the ground signal wire coming from your override switch
Relay Pin 87a - May or may not exist on your relay, but is unused regardless
BUT...per beasticles' diagram, Pin 30 and 87 are actually switched around. You confirmed this is correct. Is this mixed up in your original post? Perhaps all I need to do is switch those around? I currently have the DB/PK wire + switch ground spliced to 87. The fan does switch on and no CEL when I do turn the switch to ON.

Thanks again!
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