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Electrical Key on power for Fan relay

  • Thread starter Thread starter Nine Finger Wrenching
  • Start date Start date Jan 14, 2025

Nine Finger Wrenching

Active Member
Nov 24, 2023
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Jan 14, 2025
#1
  • Jan 14, 2025
  • #1
My question basically is do you see any problem with getting "key on" power from O2 plug to trigger fan relay?

I mounted my fan relay/thermostat on passenger side near O2 plug.
I found pin that showed 12v power when key is turned forward, but not when key is turned backward.
Don't ask me what color that wire is, I can't tell.... old wires and partial color blindness can be a struggle. LOL


I did a jumper connection with one of those little blue mash on connectors like you get with trailer lights to get signal to the yellow wire to trigger the relay.


So do you think this is okay to do? I didn't think it would affect anything with O2 since it was just triggering relay. It seems to be working great, but I would like an experience opinion on this.

Thanks in advance! ~Josh
 

Bullitt347

I have been doing it wrong this whole time
15 Year Member
Mar 23, 2007
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Jan 14, 2025
#2
  • Jan 14, 2025
  • #2
How many amps does the fan pull?
How many amps does the O2 sensor require?
How many amps is that circuit fused for?
 
Reactions: General karthief

Nine Finger Wrenching

Active Member
Nov 24, 2023
157
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Memphis
Jan 14, 2025
#3
  • Jan 14, 2025
  • #3
Bullitt347 said:
How many amps does the fan pull?
How many amps does the O2 sensor require?
How many amps is that circuit fused for?
Click to expand...
Fan is pulling power straight from battery. I'm just triggering a relay. Don't think that's a significant draw, but also why I'm asking.
 

Bullitt347

I have been doing it wrong this whole time
15 Year Member
Mar 23, 2007
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Middle of Maine
Jan 14, 2025
#4
  • Jan 14, 2025
  • #4
In that case I doubt it will hurt anything...not the way I would do it, but that is me.
 
Reactions: Nine Finger Wrenching

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,249
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Massachusetts
Jan 15, 2025
#5
  • Jan 15, 2025
  • #5
I wouldn't touch the O2 sensor harness for this.

Low coolant sensor plug at the front driver's side of the engine bay is key-on power. I've typically used this as a fan relay trigger in the past.
 
Reactions: Nine Finger Wrenching and AeroCoupe

Nine Finger Wrenching

Active Member
Nov 24, 2023
157
23
28
Memphis
Jan 19, 2025
#6
  • Jan 19, 2025
  • #6
Mustang5L5 said:
I wouldn't touch the O2 sensor harness for this.

Low coolant sensor plug at the front driver's side of the engine bay is key-on power. I've typically used this as a fan relay trigger in the past.
Click to expand...
Thanks! I'm gonna track that plug down. I may end up moving it.

Here's what I did.

View: https://youtu.be/9VOlPJ0BozM?si=M4aKa0XACKCKki6S
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
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Claremore, OK
Jan 19, 2025
#7
  • Jan 19, 2025
  • #7
Just a suggestion but you either need a shroud for your air filter or move it into the inner fender area. You can get fan wash with them exposed like that and cause metering issues for the MAF.

Really clean install and the car is looking great man!!
 
Reactions: Nine Finger Wrenching

Nine Finger Wrenching

Active Member
Nov 24, 2023
157
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28
Memphis
Jan 20, 2025
#8
  • Jan 20, 2025
  • #8
AeroCoupe said:
Just a suggestion but you either need a shroud for your air filter or move it into the inner fender area. You can get fan wash with them exposed like that and cause metering issues for the MAF.

Really clean install and the car is looking great man!!
Click to expand...
Thanks for that!! I had been looking at some of the cold air fender well kits. I totally wanna go that route. What's on here now is what came with it. Heck I've just been trying to get it to run. LOL This car was way more incomplete than what I had realized. Everywhere I turn I'm needing to buy something else to make it complete, or upgrade it. I am learning so much about this car that I wouldn'y have any other way. Gotta find those blessings!!

I REALLY appreciate you saying it's a clean looking install. That actually means a lot to me. I'm hoping to pull up to Cars and Coffee one day with the outside looking like junk, and the interior and engine bay looking awesome and clean.
 
Reactions: AeroCoupe and General karthief
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