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Modified Tech Discussion Forum for Tech related discussion for Modified XJ's and MJ's. |
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#16
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Re: Radiator Fan Override Switch (The Easy Way)
winkosmosis, depends on how you want to do it. You could splice a second relay into the heavy current wiring no problem but it's easier to splice into the low current side, requires thinner wire and less care.
I don't presently have an e-fan, because my '98 came without one installed. No CEL because the ECU only monitors whether the relay coil is open/shorted (as I expected) not whether the actual fan is operating. I'm going to my storage unit to pick the fan up and install it tonight, if I can find my set of OEM PDC terminals I'm going to get a head start on this mod.
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My yard looks like Sanford & Sons. Please do not PM me about the AW4 info thread unless you have a truly unique question that is not covered by it or info to add. I do not respond to questions answered by the thread. Definitely do not hunt down my phone number at 3AM, text me about it, and then threaten violence when I am not helpful. It will not get you what you want. CTeunuch: Sometimes I really wonder if this sport makes you insane, or it just attracts the mentally unstable. |
#17
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Re: Radiator Fan Override Switch (The Easy Way)
Quote:
If the ECU switched the relay by supplying power, then you could have a problem duplicating that with a switch, because the power from the switch would fight the ECU when both were switched on. |
#18
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Re: Radiator Fan Override Switch (The Easy Way)
You're partially correct. The ECU does switch the relay on by grounding the terminal - but what you're missing is that the ECU will notice if you ground the same terminal by yourself. It'll throw a CEL saying that the fan relay is stuck low for some reason.
What this mod does is turn the relay on without forcing the ECU fan relay control wire to ground, so the ECU never realizes you're doing anything.
__________________
My yard looks like Sanford & Sons. Please do not PM me about the AW4 info thread unless you have a truly unique question that is not covered by it or info to add. I do not respond to questions answered by the thread. Definitely do not hunt down my phone number at 3AM, text me about it, and then threaten violence when I am not helpful. It will not get you what you want. CTeunuch: Sometimes I really wonder if this sport makes you insane, or it just attracts the mentally unstable. |
#19
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Re: Radiator Fan Override Switch (The Easy Way)
Ah OK, makes sense.
How does the ECU know all this? |
#20
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Re: Radiator Fan Override Switch (The Easy Way)
Hmm... want the electrical engineer nerdy version or the easy version?
Easy version - it watches the output wire and when it isn't doing the same thing it's telling it to, it screams about it. EE nerdy version - The ECU monitors the ground-side-switched radiator fan relay drive line. When the voltage present on the line indicates it is grounded when the drive transistor is not turned on, or when the voltage present on the line indicates it is not grounded when the drive transistor is turned on, a fault code is registered - most likely P1491, Radiator Fan Control Relay Circuit (An open or shorted condition detected in the radiator fan control relay control circuit. This includes PWM solid state relays.)
__________________
My yard looks like Sanford & Sons. Please do not PM me about the AW4 info thread unless you have a truly unique question that is not covered by it or info to add. I do not respond to questions answered by the thread. Definitely do not hunt down my phone number at 3AM, text me about it, and then threaten violence when I am not helpful. It will not get you what you want. CTeunuch: Sometimes I really wonder if this sport makes you insane, or it just attracts the mentally unstable. |
#21
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Re: Radiator Fan Override Switch (The Easy Way)
The EE version made more sense. It sounds like the ECU is too smart for its own good
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#22
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Re: Radiator Fan Override Switch (The Easy Way)
I tend to agree. It's fairly shortsighted, all it does is tell the ECU that its own components are working and theoretically connected to something. It's like target shooting by listening for the gunshot instead of seeing if you hit the target. But hey, it's what we have to work with, and I'm glad they set it up that way because it makes it easier to override with a switch without triggering a CEL.
__________________
My yard looks like Sanford & Sons. Please do not PM me about the AW4 info thread unless you have a truly unique question that is not covered by it or info to add. I do not respond to questions answered by the thread. Definitely do not hunt down my phone number at 3AM, text me about it, and then threaten violence when I am not helpful. It will not get you what you want. CTeunuch: Sometimes I really wonder if this sport makes you insane, or it just attracts the mentally unstable. |
#23
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Re: Radiator Fan Override Switch (The Easy Way)
well kastien if u find the wire colors in your 98 please lemme know! i split my loom and have the relay and splices ready to go!
EDIT: wait.. what harness is it in? the bigger one on the little one? Last edited by truckntractorhick; July 9th, 2010 at 19:01. |
#24
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Re: Radiator Fan Override Switch (The Easy Way)
Ive looked over a few write ups on this issue, and I am just curious where the heck you get a relay, and where exactly do you put it if, just making he fan switched is all you want to do?
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#25
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Re: Radiator Fan Override Switch (The Easy Way)
waytekwire, delcity, most parts stores...
Truckntractorhick, the wire colors are the same on my 97, so I'd venture a guess that they didn't change between 96 and 99. Same colors as in fyr's schematic, as far as I know. You can access the blue/pink wire near the connector on the PCM- that's what I did while fooling around with a crude attempt at this. I'll have to check, but I believe it's in the third connector, the rear-most one. |
#26
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Re: Radiator Fan Override Switch (The Easy Way)
yea im still tryin 2 find them here in my garage! ive found: dark blue with, orange, gray, black, and white but no pink! unless that gray one is....... ugh i hate all these different
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#27
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Re: Radiator Fan Override Switch (The Easy Way)
I did this mod a couple nights ago because I felt like it (I have no need for it yet.) I did it by installing the relay in the PDC, though, so my findings will likely not help that much. It wasn't bad, just cutting and splicing a few wires and I was done.
__________________
My yard looks like Sanford & Sons. Please do not PM me about the AW4 info thread unless you have a truly unique question that is not covered by it or info to add. I do not respond to questions answered by the thread. Definitely do not hunt down my phone number at 3AM, text me about it, and then threaten violence when I am not helpful. It will not get you what you want. CTeunuch: Sometimes I really wonder if this sport makes you insane, or it just attracts the mentally unstable. |
#28
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Re: Radiator Fan Override Switch (The Easy Way)
pdc= ? fuse block er something?
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#29
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Re: Radiator Fan Override Switch (The Easy Way)
Power Distribution Center (aka under hood fuse box)
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#30
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Re: Radiator Fan Override Switch (The Easy Way)
Quote:
Did this same modification to my '98 almost 8 years ago and much like you it required research with the FSM and probing around with a VOM. |
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