want secondary fan to kick on with primary...

S

SCMP3

:
1993 miata
well i have a protege 5 radiator and 1 12" slim fan. did wonderful while the weather was chilly. now that the weather is warming up i need to get a second 12" slim fan. no problem.

the problem is i want it to kick on with my other slim fan(wired into the oem primary fan plug).

how would i go about doing this? i was told id need a relay to wire them in. any help would be awesome
 
Yeah, a relay would do the trick.

- Power from the battery to the relay (with an inline fuse)
- Other side of the relay to the postive wire on the fan
- Run a small wire from the positive on your current fan to the relay trigger
- Ground the relay to the chasis
- Ground the negative from the fan to the chasis
 
^^^ Exactly.

That way, you're just using the stock fan circuit as a signal to fire up the second fan, which is powered by it's own properly grounded circuit. If you just tapped into the stock fan wires, there's a chance you'd overload the fuse or wiring. Best to do it right.
 
I'm in Australia so I have no idea where you could get one in the States. Look on eBay but any electronics store will have them.

As for which one - just make sure that the relay can handle the Amp rating on your second fan. Other than that should all function the same.

If your fans draw a lot of Amps and you wanted to get really tricky, you could put a small capacitor in the signal wire which will delay when the second fan kicks on after the first fan. This will reduce the initial draw on the electrical system when the fans start. Exactly which components you need to this and how to set it up are beyond my knowledge but some Googling might yield some info.

Cheers :)
 
I was able to get a replacement 40A relay for about $6 at the local auto parts store. I'd start there. I'm not sure what the rule of thumb is on sizing fuses and relays, but I would guesstimate that double the rated amperage of the fan is a good place to start.
 
What are you trying to do by making two fans run at the same time? one 12 inch puller on your driver side of the radiator should be more than enough to keep the car cool.
 
If you wanted to get fancy, you could get an adjustable fan controller (can be had for <$40 from summitracing.com) and set it only to kick in above a certain temp. (Not sure where the stock fans kick in...)

If that second fan never turns on, then you could just remove it and make your engine bay that much cleaner ;)
 
yes im making the 2 fans cut on at the same time. i would just wire it into my ac fan wires but it wont come on seein as i dont use my ac....ever
 
id think you could just run it in parallel with your old slim fan... unless theres something im missing... check the fuse for the fans and the rated amperage. there shouldnt be any significant load from anywhere else on that circuit...
 
Same question as OP just different circumstances. I've got deleted AC. Can I just hit the AC button and expect my secondary fan to turn on?
 
I'm fairly certain the answer is no. To the best of my knowledge the AC fan kicks in when the AC system reaches a certain temp, like the rad fan.
 
Subbing. Im installing my second fan later this week. I was going to put it on a switch, but I think ill give this a try (as I have a relay already) Ill try to get the right number if you are interested.
 
Right # for what exactly?

And if anyone knew what stock msp/pro5 fans flowed cfm wise that would be amazing. Mainly for curiousity
 
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