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Manual Radiator Fan Switch -Help

General '88 - '91 Prelude Discussion
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aaron.johnson
Posts: 2
Joined: 28 Aug 2017, 17:44

Manual Radiator Fan Switch -Help

#1

Post by aaron.johnson » 26 Sep 2017, 12:31

Hey, so during the summer and during bumper to bumper traffic, my car starts to get really hot so I wanted to add a switch to over ride the computer and turn the fans on. What would be the best way to go about this? I was going to run a wire from the fuse box hot with a fuse in it to a switch, then run the other side of the switch right to the hot that turns the fans on. I don’t know if this is the best way to do it so I’m looking for a little guidance. I would really not like to use a relay to do this either. If anyone has a link to a write up for our cars that’d be sweet but I couldn’t find one.
Thanks in advance!

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MustardCat
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Re: Manual Radiator Fan Switch -Help

#2

Post by MustardCat » 26 Sep 2017, 18:30

A 3G Prelude will happily idle in the summer heat of Phoenix with all the accessories running and have no problems cooling - if there aren't any problems with the cooling system or fan control. So what you are wanting to do is to essentially cover up a problem with your specific car. I strongly recommend finding the real problem and fixing it.

However here are two basic ways to do it:
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If you are just wanting a temporary switch then example 1 is easy. Just shove the exposed wire ends into the slots for the relay, after that shove the relay back in to hold the wires in place. Then just run the wires to wherever your switch is.

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aaron.johnson
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Joined: 28 Aug 2017, 17:44

Re: Manual Radiator Fan Switch -Help

#3

Post by aaron.johnson » 26 Sep 2017, 20:31

Thanks mustardcat ❤️. I haven’t gotten it to overheat while idling. I turned the car on and let it sit in the sun for like 20 minutes. But as soon as I turn the car on and get caught in traffic, the temps start to go up. If I get a break and can go more than like 15 mph, the fans come on again. I’m heading to h2o on Friday night and I really don’t wanna get caught in traffic on the coastal highway and have to keep shutting my car off. Other than traffic, the fans work perfectly, they even run when the car is off like it should.

bryn.clingwall
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Joined: 12 Feb 2018, 16:25

Re: Manual Radiator Fan Switch -Help

#4

Post by bryn.clingwall » 12 Feb 2018, 16:31

any ideas on how to run this switch and keeping your stock control as well? I ran one just like you have it in the second diagram but kept the line to the relay. Cant keep fuses in it. Im no electrician but if theres already 40A running to it and the stock relay switches on sending another 40A does it equalize or go to 80A or..?? I have my A/C condenser fan hooked up the same way and no problems.

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MustardCat
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Re: Manual Radiator Fan Switch -Help

#5

Post by MustardCat » 13 Feb 2018, 03:46

You can leave it hooked up just like the in second pic, as long as the switch is off it will function like stock. It's the fan motor that draws up to 20A, so it doesn't matter how many power wires you have running to it, it wont go above 20A (unless there is an issue with the motor itself).

If you keep blowing the fuse (the one in the fusebox or one on your switch?) I would make sure the switch wires aren't shorting out anywhere. If it blows instantly it's most likely a short, if it works for some time then blows then it's more likely the fan motor motor is drawing excessive amps. Might need a new fan motor.
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justchiken United States of America
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Joined: 28 Feb 2018, 16:14

Re: Manual Radiator Fan Switch -Help

#6

Post by justchiken » 10 Mar 2018, 20:20

I just want to add this on to this thread. I was having problems with my radiator fan not wanting to turn on. Took me while to figure everything out but it turns out the Prelude has a box that keeps the fans on after you turn the car off if the engine bay is over a certain temp. Something in mine had fried so I figured out a way to bypass it. The box is underneath the passenger footwell side panel, it's a brown rectangular box. All I did was unplug it and splice the black/yellow(1, pin #2) wire to the red/green (pin #3) wire. Looking at it again, you could just jump the two pins with some wire instead of cutting. If the image ever goes down, I'm referencing page 16-30 of the online service manual. Now the fans turn on whenever the temp switch turns on. My AC does not work so I am not 100% sure if this will mess with the AC condenser fan, but at minimum the regular radiator fan will work. I'm pretty sure you could also splice in the yellow/black (pin #1) wire along with the other two and make both fans turn on when the temp switch turns on, but then I don't think it will turn on when you turn on the AC.
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