Currently I have dual electric fans, each on their own relay, that both come on around 180 degrees. I would like to reduce the fan noise from both fans coming on at once since my system stays cool easily and both fans tend to be overkill. I was thinking about having one fan come on around 180 degrees and the other come on if the temperature raises 10 degrees or so above. Fans 1 and 2 would also shut themselves off once each one dips 10 degrees below their set temps.

I see Jegs sells a kit that appears to do just this for around $150 that would control both fans. http://www.jegs.com/i/Derale/259/16789/10002/-1
Another possibility, would be to let Fan 1 continue to come on at 180 using the temp sender Renegade supplied, disconnecting the Fan 2. Jegs also sells the same adjustable unit for a single fan for $83. I would connect Fan 2 using the single controller for half the price. http://www.jegs.com/i/Derale/259/16779/10002/-1

What are your thoughts?
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Look at the 944 setup.....junkyard maybe.
I believe it's a two stage fan setup at two temps.

Can you switch with ground? If so (and courtesy of BIGKAT83) use the diagram a few posts down. All you would need to add is one more relay then reconfigure the wiring a tad. http://www.914world.com/bbs2/index.php?sho...=226470&hl=

An easy way is to use two sensors. Use one for inlet temp and the other for outlet temp. Set the inlet say at 210 and the outlet for 180.

cheaper would be to install a second temp sensor for one of the fans, in the incoming hose to the radiator using a threaded hose splice ?? maybe ??

http://jagsthatrun.com/Pages/Parts_DATZ_Ho...er_Reducer.html

Two sensors sound like a super simple way to accomplish what I wanted. Why one at the inlet and one at the outlet? Would it really matter where the sensors are placed since they both would be different temp senders?

The inlet splice sounds pretty easy as well.

Just read BigKat's setup. Since I have two single speed fans, I like how he turns on both at 1/2 speed and then, only if, the temp rises to 190 then they kick on at full speed. All with three relays.

Question. Looking at his diagram, would the two different sensors represent the ECU pins (C1, C2) if I'm using standard sensors at not a ECU to trigger the fans?

Does it matter where the sensors are mounted?

You could use something like the Audi/VW/Porsche 944/928 radiator fan switch that has 2 switch that operates at 2 different temps.
Stock is something like 95 deg C and 102 deg C, or aftermarket switch available with temps of 85 deg C and 92 deg C.

Audi used a large resistor and ran both fans thru 1 stage of the resistor for low speed and bypassed the resistor for high speed.

Jim

Correct on the c1/c2 pins. I would think that any N/O temp sensor(s) would work. Just need the circuit(s) to close to ground instead of 12v. That and the added relay would work. I don't know what your power plant is but I suspect you would want the sensors located close to the block.

I too don't see any reason why BIGKAT83's setup wouldn't work with two separate sensors. I have the same setup on mine that's run by the LS1 PCM. The slow speed fans (1/2 speed) are very quiet indeed.

Andys

I would not use a sensor on the input. Only on the output. Use 2 sensors there with different temperature settings. I installed an oil cooler and mistakenly installed the sensor on the input side. This is almost always be hot enough to turn on the fan. The cooler or radiator will do some cooling without any fans used. You need to add additional air flow when the cooler itself cannot dissipate enough heat.

I recently installed a Painless F5 controller for the Renegade setup for basically the same reason; when those fans come on, you feel like you're driving a hovercraft (plus, the lights dim something fearsome).

Apart from having to make an adapter for the sensor in the radiator it went smoothly and the result is a big improvement, although even at 50% the fans are still fairly noisy.

The PWM isn't entirely smooth, so now at a stoplight at night with the fans running the headlights flicker a little, but overall temperatures haven't been cycling up and down like they used to - it gets to around 180 and then just stays there.

Tom clued me in before I went too far. He had me run an 8 and a 10 ga. from batt to my power block in the front hood just to avoid that exact problem. Thx again Tom

Even with a direct run from the battery, the lights will dim a little when the Renegade fan set kicks in; the cold draw from the two fans is around 30A. The F5 could be smarter, but the alternatives all seem worse.

Put both fans in series. They should run at half speed.

The schematic above might be doing just that but I would have to draw all of the relay internals to see what it is doing.

you could theoretically have three settings.
One fan
Both fans half
Both fans full

oh DUH....

My Eurovan has this.
Look for the temp sensors (and associated inline hose fittings) on a 1993 VW Eurovan parts diagram. There is a plastic housing for the standard Bosch sensors that fits a stock size rubber hose...

As stated above, both sensors are on the outlet side of the radiator.
Three sensors all together, two of them run the fans on separate circuits.
One more for the ECU.

The circuit logic in BIGCAT83's schematic (how GM designed it) switches from series (low speed) to parallel (high speed; each fan now sees 12V). The LS1 PCM also turns those fans off when the vehicle exceeds 40 MPH. Mine utilizes this feature, since I added a VSS to the axle CV.

Andys

With both fans on high I get a .03v drop across the 8 ga. I haven't checked the drop off the 10ga yet. I'm hoping I don't notice any dimming once it's on the road. Is the Renegade set up a power hog?

Lots of great information. OK. I'll run two different sensors on the output side of the radiator. I already have one sensor there already. I can add one more to the outlet hose ( or use Eurovan setup as noted). I do have a another port in my radiator (see picture) that I may be able to use. It's used for burping the radiator--not sure how the temps are at that point.

After reading everyone's comments, I'm now thinking about the issue of having the fans, as noted, shut off at cruising speeds. Not sure how necessary this extra luxury would be in my case (no ECU, etc, unless my MSD has that ability).

I seriously doubt my fans would need to run if I was cruising at highway speeds. At best, the temps would drop enough to turn the fans off anyway, or at least 1/2 speed.
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When I had my overheating problems (and still do..) I could notice a major difference when the fan was on and the fan being off at 70mph. Granted this was a big ass 2300cfm fan, but still.

c1 and c2 represent sensors that when active create ground (relay pin 85)?

does relay 3 have battery hot at pin 30??

in bigkat's graphic.

does the high speed and low speed work together or is one off when the other is on?

Yes, c1 & c2 are grounds which when are controlled (in my case) by the ECU. They provide the ground at their respective relays. #30 pin on #3 relay is getting it's "hot" from fan #2. The fans run together at hi or low speed. Or, they are off. They do not run independent of one another.

thanks : )

back to graphic.

I went ahead and totally rewired my dual electric fan setup using three relays and BigKat's diagram.

The only thing left to do is purchase a thermo switch to screw into my rod simpson radiator where their is an extra port that is capped at the top of the radiator. I brought the plug with me to my FLAPS and they couldn't figure out which one (application) that would screw in...GEEZ! I thought that would be the easy part.

Any ideas how to source a 200 degree sensor that is the right size for my radiator?

http://www.summitracing.com/search/departm...size/3-8-18-npt

Assuming is is a 3/8" NPT thread...