To Relay or Not To Relay... (extra cooling fan)

[davew833]

So my mom's '94 Chrysler Lebaron has had warm-weather overheating issues lately which I finally solved by adding an extra 12" 'pusher' fan on the front of the condenser to augment the woefully inadequate SINGLE electric cooling fan on the other side. At the moment, the additional fan is wired to a heavy- gauge cord (think 120v lamp cord) with a fuse-protected cigarette lighter plug which plugs into the lighter. The plug and the first few inches of the cord get fairly warm, but the fuse is holding fine.

Of course the whole system is shoddy- looking and unswitched... I have to remember to unplug the fans or... dead battery. I'm fine with the fans not coming on automatically so I'll have them on a switch, but I'm planning to put them on a switched circuit controlled by the ignition key if I can find one to tap into. A fuse, of course, is a "must", but should I put a relay in the circut somewhere? What does a relay really accomplish?

[oab_au]

Originally Posted by davew833

So my mom's '94 Chrysler Lebaron has had warm-weather overheating issues lately which I finally solved by adding an extra 12" 'pusher' fan on the front of the condenser to augment the woefully inadequate SINGLE electric cooling fan on the other side. At the moment, the additional fan is wired to a heavy- gauge cord (think 120v lamp cord) with a fuse-protected cigarette lighter plug which plugs into the lighter. The plug and the first few inches of the cord get fairly warm, but the fuse is holding fine.

Of course the whole system is shoddy- looking and unswitched... I have to remember to unplug the fans or... dead battery. I'm fine with the fans not coming on automatically so I'll have them on a switch, but I'm planning to put them on a switched circuit controlled by the ignition key if I can find one to tap into. A fuse, of course, is a "must", but should I put a relay in the circut somewhere? What does a relay really accomplish?

Dave you should use a relay for the new fan, to prevent the wiring from heating up, to reduce the power to the fan. Connect the relay to turn on, when the original fan turns on.

Harvey.

[Hocrest]

Yes to the relay.

For the trigger to the relay, just tap into the stock fan harness. With the relay you won't be adding anything to the existing circuit, and you won't need to remember to turn it off to keep the battery.

[Landshark]

A relay allows a low current ckt to control a high current one - flip a small switch and it triggers the relay to draw current directly from the battery to the fan. No need to run high current wiring to the interior to the switch and then back to the fan.

[nsm484]

Originally Posted by Landshark

A relay allows a low current ckt to control a high current one - flip a small switch and it triggers the relay to draw current directly from the battery to the fan. No need to run high current wiring to the interior to the switch and then back to the fan.

^^ agreed

My Bro-InLaw has not listened to me on this, and has burned out 3 switches so far to his custom fan on his '85 300zx....

[Conn SVX]

I tried to tell a guy just the other day, not to hook up a fan directly to the battery. He was leaving for Fla. and said he was putting a switch on his fan because the sensor was shot. I told him he needed a relay. When in doubt put in a relay.

[davew833]

Thanks for the good answers guys- can someone enlighten me about how to pick out the correct relay?

[oab_au]

Originally Posted by davew833

Thanks for the good answers guys- can someone enlighten me about how to pick out the correct relay?

http://www.ebay.com.au/sch/items/_W0...sid=m270.l1313

Harvey.

[davew833]

Thanks Harvey! Turns out it would be easier to wire it with a relay than without, actually. Here's a good explanation I found:

http://www.mp3car.com/the-faq-empori...ire-it-up.html