Two elec fans, two switches or one

[willyT]

I picked up two elec fans, one 14" about 2000 CFM, other 12" about 1200 CFM
Total is 20 amps for both.

I figure I could run them both off 30 amp relay.
I was looking at 180° on 170° off fixed.
Or should I go with fixed control plus a adjustable to stage them with two relays.

Whats most common on dual fan setups.

Thanks
WT

[GREASEMONKEY72]

if you dont have the mechanical fan i would just let them run, but if you have a mechanil fan then id put them on a switch

[1970shortbed]

mine were on my truck when i bought it but they( i have two) are hooked up to a relay connected somehoe to the temp sensor and come on and off by themself with no switches

[Longhorn Man]

GM72, hate to disagree with you, but "just letting them run" will cit the life span by years, and puts way too much of a load on the charging system.
I would wire one to come on at 190 or so, and the other at 200, maybe 210. I wouls also do a buck up toggle to control both, since a simple blown relay could leave you stranded in a puddle of overheated green goo.
When you are goin down the freeway, the fans will never come on... so if you have them on all the time.... then all the freeway time would be puttin wear on them, and 95% of the time over 45 MPH they are off too, so that's even more time on when not needed.

In all reality, it is pretty much impossible to beat a good mechanical fan with a clutch... pretty much fool proof.

[willyT]

[QUOTE=Longhorn Man;2222748]GM72, hate to disagree with you, but "just letting them run" will cit the life span by years, and puts way too much of a load on the charging system.
I would wire one to come on at 190 or so, and the other at 200, maybe 210. I wouls also do a buck up toggle to control both, since a simple blown relay could leave you stranded in a puddle of overheated green goo.]

Thanks,
I'm going to run temp switch, but not sure on temps to bring them on.
And if it's best to stage start them with two diff. temp sensors.

[OLDIRON69]

Originally Posted by Longhorn Man

GM72, hate to disagree with you, but "just letting them run" will cit the life span by years, and puts way too much of a load on the charging system.
I would wire one to come on at 190 or so, and the other at 200, maybe 210. I wouls also do a buck up toggle to control both, since a simple blown relay could leave you stranded in a puddle of overheated green goo.
When you are goin down the freeway, the fans will never come on... so if you have them on all the time.... then all the freeway time would be puttin wear on them, and 95% of the time over 45 MPH they are off too, so that's even more time on when not needed.

In all reality, it is pretty much impossible to beat a good mechanical fan with a clutch... pretty much fool proof.

I agree, after the body lift on my S-10 I went with an elec. fan and a toggle. The fan lasted about a year, lifetime warranty and a new sender set up and I can control the temp. Only way to go. I wired a light, small alarm red light to let me know it is running. Just piece of mind.... If your relay craps out, I ran the wire in plastic loom, left extra wire for just in case situation, I can run it straight to the battery to get me home!

[68alltheway]

you really only need the 14 inch, no need for the 12 inch. as far as switchs go, you could just go with a toggle or thermostat, the only thing you want to think about is if other people other than you drive it, you have to make sure that they know to cut the fan on. i installed a 16 inch the other day and hooked it up to the ignition for now until the i get my thermo. especially since its summer, you might as well run it the entire time. here is a pic of mine.

[RetroSBK]

I run one 14" puller on a relay and 180 temp switch. It also has a manual bypass switch in the cab. I have a second 14in set up as a pusher, mounted on the A/C condenser that turn on whenever the AC comes on. It also has a manual bypass switch.

Never can have it too cool! Be sure to run each with a realy and a fuse!

Will

[Rupdog]

get a thermo switch that's preset to come on at 180. they're around $20-30. use that on the primary, through a 25-30 amp relay setup, including a manual "on" toggle. the red indicator light is a nice touch too.

wire the secondary fan to your a/c setup, to come on whenever the a/c is. remember to also use a SEPERATE relay on this fan, but can put both through the same manual "on" toggle.

this way you're protected in all situations.

i'd suggest finding a 94-96 caprice/impala/roadmaster. these have awesome dual fan, dual relay setups, and are all over the wrecking yards. swipe the heavy duty relays from these donors. they're dark green, and located on the pass side firewall. grab both relays, along with the nifty wiring harness, since it uses GM WeatherPak connectors for corrosion protection. i'd also find a third relay, and throw it in the glove box as an emergency spare.

i have this setup on my 67 RS camaro.

wew! that was wordy. hope it helps....

[brak]

I use a fan controller manufactured by derale (cost $39) on a couple vehicles.



basically it's a relay, with a temp sensor, that is capable of controlling 2 fans, and it works great. it has a pot to adjust at what temp the fans come on, only runs a single fan when the second isn't needed, and has a connection, to start the second fan when the A/C comes on...

This is a no brainer...
takes 10 minutes to install,

[Jim_PA]

Why have them come on at such low temps? Mine worked perfect with on @ 200, and turned off @ 185.

I would run a separate relay for each (for case of relay failure as already mentioned)