i have dual electric fans hooked to a toggle switch, when i switch it on after about 5 minutes the toggle switch gets hot. i was told that i need to put a relay on the fans.?? do i need one? and how do you wire it in?

lemonice,
here's a wiring diagram.
only diff is instead of fog lights, you will have your fans.

http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/foglites.htm

david

If this is not clear, what 6t7 is illustrating is that you use your toggle switch to activate the relay and the relay will handle the heavier load to the fans ... also, make sure you are using an adequate size wiring ... too small wiring will also be subject to heating up and it never hurts to use a fuse

You also probably need a seperate relay for each fan if you're going to use the typical parts store type of relay.

Peter

Your problem is that your switch is not rated or capable of handling the total current. You absolutely need a relay system.

First, use only automotive rated relays......not Radio Shack or stereo store junk. Go here http://www.newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/partDetail.jsp?SKU=26C0334&N=0 whereas this relay will handle it all! (the data sheet on this is wrong listing it as a 24volt Max relay. It's a nominal 12volt automotive relay, so the numbers are correct for part numbers)

Here is a typical diagram for wiring up an application with fans and with air

http://www.geocities.com/smithmonte/Auto/FanControl.jpg

thank you guys for the info, thats what i needed. i will wire the relays in this weekend. i was always worried about that toggle switch getting hot and leaving me stranded, or worse a electrical meltdown.

Just a quick question.............the above diagram shows two relays with only one fan. Is there a reason I would need two relays for one device? Any help is appreciated!!

Thanks,

Just a quick question.............the above diagram shows two relays with only one fan. Is there a reason I would need two relays for one device? Any help is appreciated!!

Thanks,
That diagram as two relays because of the AC. One relay turns the fan on when the AC is on. The other relay turns the fan on based on thermal switch or manual switch. If you don't have AC then you certainly don't need the relay shown that is hooked to compressor clutch circuit.

what is the led for in the drawing? and if you have the windstar fans with one being a two speed would you need 4 relays if you have air? thanks

what is the led for in the drawing? and if you have the windstar fans with one being a two speed would you need 4 relays if you have air? thanks
Only purpose I see for the led is an indicator that the fans are on.
As for how many relays with 2 fans, one a dual speed, well there are lot's of possibilities. How are the fans to be controlled? Low and high on dual speed fan, temp controlled? High speed on the second fan, temp controlled? Does 2nd fan go on when first goes to high speed? You want both on high if the AC is on? Not sure how you want it to work so I can't say. It would take at least two temp sensors and 3 relays.
Maybe low speed on the one fan when the ignition is off, temp controlled, but that would only be good if you had an electric water pump, to cool engine after it is shut off.

Where did you get the fan setup? Maybe search the web for a similar setup.

That diagram as two relays because of the AC. One relay turns the fan on when the AC is on. The other relay turns the fan on based on thermal switch or manual switch. If you don't have AC then you certainly don't need the relay shown that is hooked to compressor clutch circuit.

Thanks for the info! I am new to all of this and had a hard time understanding the two relays in the diagram! Luckily I have a one speed fan and no AC so my setup will be fairly simple.

Thanks again!

Thanks for the info! I am new to all of this and had a hard time understanding the two relays in the diagram! Luckily I have a one speed fan and no AC so my setup will be fairly simple.

Thanks again!
Yea, if you delete the relay on the right and the wiring associated with it you should be all set.

well they are windstar fans from a 98 van two fan setup one fan is a single speed the larger fan is two speed what i wanted was to have one come on with a temp switch in the block if that will keep it cool in normal conditions haven't figured out how to have the other come on on low if the temp rises maybe just a bypass toggle and then have the high come on when the a/c is on or maybe i should just have the two low fans come on at the same time and have the high speed come on with the a/c what do you think? thanks Ed

well they are windstar fans from a 98 van two fan setup one fan is a single speed the larger fan is two speed what i wanted was to have one come on with a temp switch in the block if that will keep it cool in normal conditions haven't figured out how to have the other come on on low if the temp rises maybe just a bypass toggle and then have the high come on when the a/c is on or maybe i should just have the two low fans come on at the same time and have the high speed come on with the a/c what do you think? thanks Ed
Well the second option is a little more straight forward as it only requires one temp sensor and 2 relays. The first option would require either a second temp sensor or switch and a third relay. Your first option pretty much matches the diagram above.

would i need a diode for both fans and the high and low. Finally thanks Ed

would i need a diode for both fans and the high and low. Finally thanks Ed
Yes, or you'll burn up your relay contacts in short order. Dissipates the energy created by the fan when it is free wheeling, after relay opens or caused by air movement when your driving down the road.

Edit: You need a diode for each fan circuit, so if both fans are on one relay, slow speed thats one diode. Easy thing is one diode across each relay, that way you know you covered and protecting the relays.

Yea, if you delete the relay on the right and the wiring associated with it you should be all set.

Thanks again for the info, as I do appreciate it! One last question............I see you are using a fusible link for the main power to the relay that supplies the fan. Is it possible to replace this with a fuse or circuit breaker and if not, what is the advantage of the fusible link?

Thanks again for all your time!