Clutch Fan vs Electric - wiring for a/c?

[jmgtp]

Hello All,
Not a 60v6 but same concepts apply. This is in regards to my '06 Dakota 4x4, 3.7L Auto. 80k miles.

I know converting to an electric fan from the stock clutch fan isn't going to show much gain, but every little bit helps. It was also very little financial cost since I already had a fan from a Nissan Sentra so I only needed to buy the controller.

Prior to the electric fan install the temp gauge had not ever exceeded the 1/2 mark, it usually sits at just a notch below 1/2. So I installed the fan, wired it up and turned the thermostat on the controller to the highest setting (something the motor would never exceed). Then I let the truck idle up to temp - no fan running. I allowed it to exceed the 1/2 mark by a good bit then I turned the fan on. It brought the temps right down very quickly - OK fan can do the job. Next step was adjusting the thermostat on the controller. So, again I idled it until the engine hit the 1/2 mark then I adjusted the thermostat so the fan kicks on at that point. It seems to work very well, when it kicks on it will cool until the gauge reads just below half, which is where the truck normally runs.

Now, the issue I'm thinking of is what happens when the coolant isn't hot enough to necessitate the fan to run, BUT you have the a/c is on. Well, I gave it a try and with no airflow, the condensor gets incredibly hot very quickly and there is not much 'cool' output at the vents. So, it clearly needs airflow any time the a/c on.

It's easy enough to wire up a relay that is closed the by a/c circuit to power the fan. But, this also means that anytime the a/c compressor clutch is engage the electric fan will run - even at 60mph down the highway. I don't like that very much. On computer controlled fans, when the a/c is on the fans will turn off over XX mph. Not sure how to achieve this on my aftermarket setup.

The only solution I can come up with is to get a 2 speed fan and wire up the low speed side to run with a/c compressor. It'd still run all the time the a/c was on, even on the highway, but that'd be better than running full speed constantly.

Is there anything else I can do to energize the fan when the a/c is on only when the truck is at a stop?

[geoffinbc]

Well unless you have a VSS sensitive controller you cannot. The Painless Performance Pulse Width Modulated Fan Controller can do this. I have one on my Trooper but never hooked up the VSS Sensitive part of it.

There is no harm in running the fan at freeway speed. If there is enough air flow across the rad the fan will be at virtually no load and won't draw much power. If you go fast enough you may actually over speed the fan and generate power

[jmgtp]

I wasn't concerned about the power draw but more so the fan longevity but I guess I don't have much choice, I'll wire up a relay with the signal from the a/c clutch. I might look into a bigger/better fan in a few months. I'm not worried about the motor overheating, the radiator is so big that even with no fan I couldn't get it above the 1/2 mark without revving it at 2500 for a few minutes straight, but I'd like to see something that can move more air for the a/c come summertime.

For the time being I'm hoping for some seriously better MPG numbers - and no I don't think the e-fan alone will get me there. My last tank accomplished a staggering 11.4 mpg. I attribute that to using the remote start often, the cold air and the short distances I drive, coupled with a heavy 4x4 truck - but more than anything else I found severely worn spark plugs, the worst I have seen out of any motor. No doubt the originals with 80k miles and they were so worn that the gaps measured near 0.08, the spec of .035! I'm suprised it ran as well as it did.

[talon2swords]

I was thinking about putting electric fan in my 2002 S-!0. Then I read somewhere that electric fans get there power from somewhere, that being making the alternator work harder, which uses more gas, so there is little benefit. So I forgot about it.

[jmgtp]

Yes, the electricity needed to operate the electric fan isn't free so the alternator does need to do more work to power it. But your missing the huge advantage of the electric fan - it does not operate continuously.

Clutch fans, spin ALL the time. Even if your engine is stone cold it is spinning. Even while you go down the highway, it spins needlessly ALWAYs consuming power. The electric fan is controlled by a thermostat and therein lies its advantage. It only spins when needed and therefore only consumes power when needed. Fact is, that as long as your moving there is enough airflow over the radiator to not need a fan. In my research before deciding to convert to an electric fan, most people report about a 1mpg gain over a clutch fan. Some say the engine revs quicker, makes less noise and feels more powerful. I can't report any first hand finding since I've only had the electric fan installed for a few days. If anything I'm glad to save all that weight from hanging on the waterpump pulley, that certainly can't be good for its bearing life.

[geoffinbc]

Plus less load on the water pump bearings.

GM Ford and Dodge have all switch to electric fans on their trucks in order to improve fuel mileage. I know GM has used them since the 90's as an assist to the stock fan.

My brother saw an honest 1.5mpg on his 97 Sonoma ZR2. I never recorded my improvements but you sure notice the peppy feel and lack of noise.

[jmgtp]

I'm at a half tank now since I swapped the clutch fan for electric and replaced the spark plugs... and I've driven nearly as many miles as I did on the last FULL tank. I'm currently at 170 miles driven, since I'm at half tank now lets say I can get double that, or 340 miles. 340miles / 22 gallons = ~15.5 mpg. Not that bad considering I do mostly city driving (the truck is rated 15cty/20hwy). I know the gas gauge isnt the most accurate thing and I won't have real numbers till I fill up. But, going from 11mpg to an estimated 15mpg is HUGE - I attribute most of the increase to the new spark plugs, driving more cautiously, and using the remote starter less but the electric fan certainly can only be helping.

I'd love to get ~18mpg out of this truck but I don't know if thats really feasible. It seems like it is finally in a proper state of tune and I drive it like your granny. I even opt for more fuel efficient routes. I'd consider a tonneau cover but I don't know how much they really help vs their cost. And is it a pain to roll up if I need to haul something bulky?

[neophile_17]

My truck came with a tonneau cover. It's the snap kind which I thought was cheesy at first but actually works well. I'd buy it if I didn't already have it. It keeps things mostly dry and 90% of what I put back there fits without taking it off. Even when I do take it off it's not so bad. You develop a method and it becomes muscle memory like tying your shoes. It helps on the highway more than around town. My totally unscientific guesstimate based on mpg figures of others with my truck is that it's worth 1 mpg. Making a 7 hour trip at least once a month, it's definitely worth it for me.

~sam

[talon2swords]

Ok. I have to refurbish my 2002 S-10 4.3l after I get caught up on some bills. I'll be installing a new LIM, removing that plastic orange slice thing off the throttle choke plate, installing a new spider injector assembly,along with a little port matching if it seems to need it...and now maybe a new electric fan all at the same time!

[jmgtp]

Official numbers are in.... 14.7 mpg. Sure that sounds pretty awful, but its a big jump from the ~11 I got on the last tank.
Again, I don't attribute that all to the electric fan and more so to replacing the very worn spark plugs. The 14.7 tank also included probably about an hours worth of idling and stand still reving while I adjusted the kick on temp for the fan. I'm hoping still do get the truck in the 16-18 range with more careful driving.

Talon2swords, the controller for the fan is pretty cheap - I believe I paid around $15 at the local parts store. You'll also want to pickup a spare 12v automotive relay so you can wire the fan to kick on when the a/c clutch is engaged. I had a free fan from a nissan sentra but I do want to eventually upgrade it. Many people use the early/mid 90s Taurus fan which costs between $50-125 depending where you look.