One Relay or Two

[srduster340]

I'm installing a dual fan assembly from a 2001 Dodge Intrepid that originally used 2 relays. One for hi speed & one for low speed. My question is, can't I use one relay and one circuit breaker for both fans in one speed only? I've included a wiring schematic for reference. I'm wondering if they will provide enough cooling for a 414" stroker with well over 400hp with a Champion 26" radiator. I have no idea how much CFM they flow. Any comments, suggestions, feedback?

 

[RedFish]

Each fan can pull its own 30 amps or more in some conditions so 2 relays are required even if both energize by the same signal.

 

[pishta]

I bet the high speed one is all you;ll need. Maybe run the low at all times and have the high kick in over 210...OR shut all both down at start for fast warm up. I know they make a lot of noise both blowing all the time.

 

[67Dart273]

Your diagram is too damn small for my old eyes. Why are they showing TWO motors? Do they actually have two separate motors, one for low and one for high? Or do they bring the motors on separately, IE "staged?" Or is the diagram wrong.

 

[mischiefdart]

I could be wrong but they could be achieving two speeds by running the motors in parallel and in series. You could run them all or nothing but two speeds would be easier on the charging system.

 

[67Dart273]

I finally managed to blow up the diagram, and while blurry, it appears that the left "low speed" motor is actually two speeds, low and high

The right hand relay (low speed) evidently runs only the low speed motor on low

The left hand relay (high speed) evidently runs the low speed motor on high speed as well as powering up the high speed motor.

So I'd say that if high speed is all you need, and IF YOU have a relay large enough to handle the current, one relay is all you need.

 

[srduster340]

Sorry for the blurry diagram. It was an internet picture. There are actually 2 fan motors. I connected my power probe and grounded both motors and powered up either the low speed or the hi speed wire and both fans come on. Originally the PCM controls whether they operate in low speed mode or high speed mode. The heavy wire that's hot at all times has a 40 amp fuse for protection and the hot in start or run wire is protected by a 20 amp fuse. I figured I could use a 40 amp circuit breaker and a 20 amp fuse as the factory did to have the same circuit protection. Funny thing is, the fan assembly is exactly the same width as my radiator once I cut off the factory mounting tabs. Thanks for the comments, suggestions fellas.

 

[Rice Nuker]

yea it appears that one motor is a two speed and the other motor is on off.

the first motor runs on low and high, the second runs on high only.

Two relays and a dual fan controller is what I would use. Or you could get two independent fan controllers, one set at like 190 and the second set at 200.

That way you use less current and make less noise when high is not needed.

[ame="http://www.amazon.com/Derale-16788-Amperage-Controller-Probe/dp/B004XONX8U/ref=sr_1_15?ie=UTF8&qid=1357272313&sr=8-15&keywords=dual+radiator+fan+controller"]Derale 16788 High Amperage Dual Fan Controller Push In Probe : Amazon.com : Automotive[/ame]



All in one unit.

 

[srduster340]

My Ron Francis fuse box has a cooling fan relay/wiring built in and I want to use it for one fan and simply buy another kit for the other one. Lots cheaper than buying a dual controller. Derale has lots of negative reviews so I will stay away from them. Lol.

 

[Rice Nuker]

Oh yea. Did not know that about derale. They are expensive generally it appears.

What are you triggering your primary relay system with ? Does the unit include a sending unit connection or sending unit?

I am running this on a dual fan (simple on off) system and it was reliable all summer. We only put 500 miles on the 440 this summer , it was 101 as we climbed thru the mountains one day.

Stuck the probe in the cool end of the rad, adjusted it to activate about 190 (engine temp) and it cycles nicely all the time.

http://www.summitracing.com/parts/hda-3647/overview/

My Ron Francis fuse box has a cooling fan relay/wiring built in and I want to use it for one fan and simply buy another kit for the other one. Lots cheaper than buying a dual controller. Derale has lots of negative reviews so I will stay away from them. Lol.

 

[srduster340]

I haven't hooked the system up yet. I need to order the wiring and sensor that control one of the fans. I plan to run power to a switch in the dash to turn the fan on in case the sensor fails. I might try that Hayden system to control the other fan. Are you using one system to control 2 fans?

 

[Rice Nuker]

We run this relay kit on a dual fan factory Jensen cooling system. Car has about 25K original and has been garaged so it is in great shape. (Valve covers were done by Leanna last spring)

The fan motors and blades are archaic but seem to blow a very powerful volume of air.

Our problem is the motors are behaving a bit wierd, one runs a little slower than the other, the bushings were dry from sitting for years (25 in a grarage in New Mexico) and I attempted to refurbish the motors but didnt get the armatures lined up perfectly with the induction field I dont believe. I am probably looking into replacing the motors with new blower motors off chrysler non ac heater fans.

but the relay kit works like a champ. I tested the amp pull on the motors and they did not pull 40 amps constant combined, so I went with a 1 relay kit.

Like I mentioned, i pushed the thermocouple bulb into the fins at the cool side of the rad, that way if the rad was cooling fine from forced air thru, the fans would not respond, but when the cool end got hotter from lack of air flow, the fans would kick on.

I should add that this unit I linked to has two power out leads, one for each fan and it turns them both on simultaneously. In our application this is how the factory had it, but the factory electronics, much like Mopar are not only old as hell and full of spiders but were severely anemic fin design so I just cleanly bypassed the factory system and left it in place in case of restoration needs.