Cool bean

I searched previous threads for wiring dual electric fans. (lots of good info!) I'm looking for a clear direction before starting the install. My next mile stone is to get condenser/radiator/fans/wiring installed before dropping engine & trans in.

Here's my facts & assumptions:

• 74 coupe, engine bay is empty, dash is removed, all wires exposed.
• Engine is Gen 1 SBC, carburated. Performer RPM intake.
• CS130 alternator is part of serpentine & accessories upgrade.
• A/C car.
• control arms are stock
• I'm fabricating fan shroud from aluminum.
• fuse panel is stock, engine wiring harness is new.
• I'd like to utilize multiple relays to confirm fan(s) on at half speed, then full speed, one fan on, then two fans on, maybe even fans off.
• trans-cooler will be mounted in front of AC condensor.
• all weather-stripping/seals will be installed.
• I'm on a budget and will be assembling from scratch. (Dewitts looks awesome...but not in the budget.)

My questions:

1. Is there a complete schematic for this type of config? (this post has a good schematic from @Bad Bird and others)
2. In addition to wiring I'm looking for how to wiring in temp sensors, where they go, and how to wiring in "both fans on full when AC is on".
3. Can anyone point me to a complete parts list too? (hey i can ask, at least!) for wiring relays, power, what gauge wire goes where, etc.

This is big ask, so big-thanks in advance!

SwampeastMike

You seem to be describing a three--if not four--speed system. Such would require multi-speed fans. Do you have such?

The two speeds obtained in the link you provided occur only because BOTH fans run at the same time at about half speed when connected in series and full speed when connected in parallel. For a two-stage temperature switch (this means that one contact closes at a lower temperature than the next) operating two single-speed fans that schematic is ideal.

Adding hi-lo operation of BOTH fans in a three- or four-stage manner gets really difficult. Not only difficult to make happen but difficult to justify.

Please clarify what you really want to do and whether or not you want two-speed fan motors.

indicating circuits (lights) for low-hi speed fan operation and everything hi with A/C is easy to add to the schematic you referenced.

Cool bean

Ah hah! Thank you for pointing that out; no, I don't have the two speed fans.

Let me adjust: I have two fans that each are: single speed, 12 inch, 1730 CFM, 12v, 80watt, push-or-pull fans (ZAP part number RAF12). I'd like to wire them so that:

• they both turn on low, (i'm asking for this function based on feedback in other posts that starting the fans at full power puts more wear and tear on the fan and also electric system. Also, I thought it'd be a good idea to have BOTH fans running low & hi instead of fan #1 then both fans at full power so air is pulled through condenser over a larger area than just through one fan. It makes sense to me, but I'm not an expert; it's what others have posted. I'm open to another approach.)
• AC on: both fans HI.
• Higher temp threshold, both fans HI
• lower temp threshold, both fans LOW

Optionally, (is it even an option?) If there's a case to be made for turning them off, (such as key on but engine not running, during warm-up, or start-up or highway cruising) I'm open to configuring with that feature supported. But I'm looking for others who've done it to make the case. I'm just curious if there's a case and if its possible.

having indicator lights in dash would be cool. (nice to have, not must have.)

Thank you!

The13Bats

Dewitts is awesome but the champion is making lots of people here very happy at a lower entry fee,

I have made my head hurt on this subject many times but in my case I do not like any wasted radiator, that is any radiator that isn't covered by a shroud is to a degree being wasted at idle when that air flow is needed.

I then decided I wanted dual fans in my mind if one fails I have back up, then if I run one fan for low and both for high when on low the fan that isn't running that hole is the path of least resistance and will get air pulled through it rather than pulling it through the radiator from the single fan running, again wasting some cooling efficiency, some people like it that way I do not.

So I decided to run both fans 1/2 speed for low both fans full speed for high this is done with a relay set up, I want to now offer Richard a huge high five for helping me get this worked out the way I wanted it and riding his coat tails to come up with my own wiring diagram that my brain can wrap around...
I love doing wiring but Richard is a guru with it...



While I have seen many professional wiring kits set up to turn on the fans whenever the AC is on which is fine but the problem I have with that is at speeds even with AC on if the cooling system is up to par fans are not needed, and if sitting in traffic and car is up to operating temp then the fans are on anyway AC on or not, if turning on AC makes it get hotter then the fans kick up to high.

What I have learned from cooling and electrical on here is each person has their way of doing it and they feel their way is best, I feel my way is best for me and my car if a person doesn't like how I do mine, no need to waste time critiquing it I am not trying to sell it to anyone, just sharing.

The13Bats

Cool bean,
you posted as I posted,
The wire I have going to the ignition switch could go to a 12v toggle switch if you wanted more control, I had it that way in my 66, but many times left it on, the fan would run a few moments after I turned the car off like many factory electric fans do....

DUB

'Cool bean'

I want to touch on the fans being on when the A/C is being requested. I have found that the twin SPAL fans I use need to BOTH be on when the A/C is on and at idle. It has been shown to me and proven when I see the high pressure side of the A/c gets lower when both fans are on.

NOW....I do agree that it is possible that going down the road (minimal speed of the car has not been undetermined as of yet...or at least I have not seen it)...the electric fans may not need to be on due to the air being forced through the condenser is enough to keep teh high side within an acceptable pressure.

I personally would have to use my air flow meter and some way to see what the CFM's are when driving at different speeds versus what the fans are doing when sitting at idle in park. I honestly have not done this as of yet. I might when I have time to look further into this.

I have figured out a way to be able to switch the fans off when a specific speed is desired to turn off the fans.

As for people wanting to have HIGH and LOW speeds on the fans. I can state that GM is doing this currently. So this concept and design DOES have merit. Whether or not it is a must...that is a personal choice. And the reason I write that is due to the previous Corvettes that did not have that design...it took years and years for a cooling fan failure....or any serious electrical charging system problems.

AS for installing lights of some type (I prefer LED's) so a person know when the fans are on or off...is not that big of a deal. I like using the multiple LED lights....where ONE LED can be made to chance colors so there is only one light bulb...but it can change colors.

I did that on one resto-mod 57 Corvette I worked on where the red LED came on when there was a computer trouble code...but this same bulb also was blue so when the high beams were on the owner knew it....AND....IF the high beams were on and the computer had a problem..the red LED would override the blue LED and the red LED would shine. SO...the ideas and options on what you want can be somewhat limitless.

Controlling when the fans come on can done with temperature switches like 'The13Bats' has shown.

I can tell you this from experience. On the 1984-1996 Corvettes...in most cases when driving it down the road...the cooling fans are NOT on due to the factory had set them to come on around 226-228 degrees Fahrenheit....and generally the coolant temperature is at or around 200 degrees in many of the Corvettes I drive. NOW...when the A/C is on...the fan or fans would come on.

DUB

The13Bats

The issue that dub was talking about requiring that both fans be on at idle when the AC is on with the dual spals 11" doesn't surprise me
when wired one fan on for low both on for high which his description indicates but rather further instills my thoughts on a dual fan set up especially when the fans share a common shroud if one fan is off the on fan will pull through the off fans hole of less resistance not through the radiator and ac condenser higher resistance, so again why I like my fans both on low both fans on high, yes, how GM does lots of cars.

The dual 11 spals also leave a fair amount of radiator uncovered by the shroud meaning some radiator is somewhat wasted at idle helping contribute to the above issue, I have been told it doesn't matter that the radiator is big enough not to need that extra air flow, that is well and good for some but I am too OCD to think I am wasting any of that radiator I paid so much for that in turn caused me to track down larger fans with a shroud that covers basically the full core, not the cheapest but it's what I desired.


I too came up with several ways to kill the fans at speeds that didnt pop the fans on and off while town driving but found it unnecessary, I have been so lucky all my cars have ran cold blooded.
so while at speeds if the engine/coolant temp gets below the fan "on" temp, high and then low the fans will turn off....

Aren't LED's fun, I do love LEDS been puzting with them many decades, I buy big lots cheap out of Asia the multi colors are fun, I have several wiring diagrams I did that will flip flop the color or in the case of RGB blend the color for fun, when buying bi and tri color leds be sure to get the common input you desire anode or cathode and note that depending on color led's use different input voltage,

Side note, In the case of my 87 fiero if I turn on the ac the fans come on no matter what engine temp or speed...that car has a factory computer I am locked into to some degree but with my 69 I can upgrade and improve things or at the very least do things to suit me.

Richard454

Oh- found a new inexpensive piece to replace one of the relays in my diagram (AC/bypass one) AND Bats it comes w/ a LED built in!!!

TR7 PAC - it's about $15- can take positive and negative triggers that are pulse or constant - Then pulse them ( you set the number) or a timed output (can program up to 36 minutes- say run the fans after shut down) and latched outputs- really incredible what it can do.

pdf instructions http://www.pac-audio.com/PACProductD...ons_010505.pdf




Here's one being used to take a single switch to control a door lock/unlock- one push locks- two pushes within 3 second unlocks

Cool bean

Wow this is great! (This thread and drawings are getting printed out and going in my build-binder.) Thank you!

So i think i can figure out the relays, where to place them, and even better interior led indicator lights (bonus!) Can you guys suggest what is the precise sending unit/probe/or whatever is used to detect and set temp on off? Model/part number, etc. (Whatever they are, they're different that temp gauge sending units, correct?)

The13Bats

Richard will tell you the make model part number its from but my dual temp sender in my diagram is from a BMW product.....

Super popular with hot rodders doing electric fans who do not wanna step up to computer controllers.

DUB

FYI...the twin SPAL fan set-ups have a divider that does not allow the one fan if it is the only one running to draw from the 'other' fan area.

Knowing that this has been beaten to death...people can make or use what they want. But for those who may not have the ability to fabricate or want to invest in another fan system that completely covers the core...the twin SPAL fan set-up DOES work just fine. And if that minor surface area that is not covered causes for a problem..then it is NOT the fans..it is something else.

DUB

REELAV8R

I prefer the on or off approach to electric fans. Mine are like the twin spal 11" fans. Both are on or both are off. Full speed when on.
Also on when the A/C is selected on, even when moving.

The condenser temps share no direct correlation with the radiator temps.

The condenser can overheat very quickly with inadequate flow. So it is somewhat critical that it is cooled whenever the a/c is selected on.

I have had one fan relay fail and the remaining fan cooled the system with only a minor rise in temps.
Wire the two fans independant of each other. Each one with it's own electrical source and it's own relay. You can use a common temp sensor. I wired in a switch that will turn on the fans manually should the sensor fail for any reason.

The13Bats

I respect others opinions on it but I still would rather have a shroud that covers most of that expensive radiator I sprang for ( like the factory does on modern cars ) and doesn't waste some of it,

the dual 11 spals are an older design and in that decade or so many upgrades have come out that I want to take advantage of , if a person runs the dual spall 11's and are happy with them I fully respect that.....

The both off then both on is also good, I like it better than one on then both on but both off then both on has the spike when they both come on no big deal since one has to upgrade the wiring and charging system anyway,

The 68-82 corvettes didn't have an electric fan factory except the one added I believe around the 80 model year so the 68-? corvettes without that electric fan package had to rely on engine driven fans only for cooling with or without AC on,

Many people will tell you that when they switch on the AC on their corvette the temp would go up some, more drag on the engine plays some part in that and the condenser in front of the radiator plays some part too when air is being pulled through it, hot air if the AC is on then that in turn to some degree heats that portion of the radiator and in turn if it heats things enough the electric fans will do their thing and turn on,

I just do not choose to wire mine where the fans come on with AC because where it's needed at idle and slower traffic my fans are already on, but most people do wire electric fans to come on with AC and I am great with that.

My wiring allows for the use of one fan if the other goes out, or a relay fries etc etc.

The biggest point here is not which way we feel works "best" what matters is which way does the owner /builder feel is best for them, and as you see different people all have their favorite set ups and they are all working....

REELAV8R

Certainly the air being pulled through the condenser will increase reduce the effectiveness of cooling to the radiator and this in turn will perhaps and most likely reflect an increase in the coolant temps as well. What I'm saying is that the condenser gets hot much quicker than this change in coolant temp can trigger the fans to run via the rise in coolant temp.

Scenario is that it's an 80 something degree day and you are driving at highway speeds until you get to a town. At speed on this day in your black vette the coolant temps are at thermostat temp of 180*. You have the A/C running because it's sunny and your car is black.
Now you come to a town and need to slow or even stop at stop lights. The coolant is still at 180* and the a/c is still running. You fans aren't triggered until 195*. As you sit at the stop light it may take several minutes for the coolant to rise to 195* to turn on the fans if they are not wired to run when the a/c is on. Or the cooling fans may not turn on at all if you have an effecient system and you get to move every couple of minutes.
In that several minutes with the a/c on and the cooling fan off the condenser temps rise radically without airflow. Along with that temp rise pressure also rises.
This eventually trips your high pressure switch and the compressor clutch releases, effectively turning off your a/c, given there is even high pressure protection on your system.
Either way you create significantly more pressure in the system than you would otherwise encouraging leaks around the compressor shaft seal or anywhere else a weakness may exist and your a/c is now off despite you wanting it on.

That is the logic used when considering the cooling fans function.


Surprisingly I did not find it necessary to change my electrical wiring in any way. I did opt for a higher output alternator, but only to increase the idle amperage, running amperage of the stock alternator would have been sufficient.
I wired my fans to the starter lug that connects to the battery as a electrical accumulator for the start amperage of the fans. In this way the electrical system is not significantly shocked each time the fans start.

At one point I had to put the stock alternator back on when the replacement one had an issue, and it handled the operation of the fans at night with a/c running with no apparent problems. Only idle voltage was effected and showed battery voltage vs something above battery voltage with the higher amperage alternator.

DUB

I wired my quite similar when I installed them. But instead of going directly onto the starter lug. I connected a wire to the starter lug and it went over to a junction block I made to supply power to it. I think if my memory serves me correctly I used an 8 gauge wire to the junction block....due to this block was going to be feeding a lot of battery power to different added components.

I also increased the alternator (108 amp...I think) to one that charged more due to the electric fans, MSD, headlight relay upgrade,etc. I just felt that with all the new stuff needing pwoer..... I did not want to use an alternator that I felt was obviously under rated.

with that statement somewhat. The area that I feel it can not be up to the owner /builder is what the high side pressure is doing at idle. That is something that they can only control by air movement over the condenser....and may find that the fans need to be on to keep the high side pressure under control.

I have been forced to do just that like I wrote in a previous post. Both fans had to be on to keep the system from getting way to high.

DUB

The13Bats

Does that scenario only work with black cars? lol, couldn't resist, but I get your point, our xterra is black as is our fiero,

While all your logic on the condenser and fans is right on, we are applying it to upgrades we are doing that have no baseline there were no 68-82 corvettes that had electric fans only, we are going from scratch.
When we apply your AC login to the modded cooling systems we are creating we each do things differently so a blanket comparison of our different ways of doing it isn't accurate, in my case I use a BMW dual fan switch, ( curious what the BMW's that ran this switch ran for 'stat temp ) the switch comes on low at 180 on high at 195 I live in Florida where I wish 80 was the normal, but many times during the summer closer to 100 is more normal stuff in traffic that black top is super hot, well over 100.

I am a person who believe engines like a goldilocks zone to run, not too hot not too cool, the factory has to deal with emissions and hotter temp I do not.
perhaps there was some confusion in my other posts, I never said my fans do not run when the AC is on I said my fans are not wired to come on with the AC since in my case almost anytime the AC is on the fans will be on I am not concerned.
But like I said before if a person wants their fans to come on with AC go for it.

my stat is 180 when it gets up to operating temps it will pretty much stay open in our weather, since water is circulating at 180 I want the fans to come on and it does,
At lower speeds and idle in weather that calls for AC my car isn't going to go under 180 and I do not want it to, so the fans are on if the temps creeps up to 195 the fans go into high speed,

I might sound really pompous here but I have zero concerns about overheating issues because I went nuts unlike normal me being all cheap and building on a tight fixed budget years back I called Dewitts and explained to Tom I had a mild bb would have at least for a spell auto trans and then AC he felt his basic radiator would do the trick but I wanted more and he built mine custom bigger inside, which he didn't give any impression he thought I needed, while I wish he had used the bb radiator not the sb one I still know it will cool a lot more than I have, then I used fans that put out way more than the popular dual 11 spals that also cool way more than I have, my cooling system is without a doubt over kill.

I was running an alternator just over 100 amps from some 80's firebird and it worked but I could tell it was really being stressed while all my stuff was on, I stepped up to a 150 amp alternator which might to some also be overkill but for me I like having more than I need than to worry is it borderline, most newer cars have some pretty big alternators.
As far as upgrading the wiring, with my 150 amp it is a must and I find many wires on my stock 69 on the small side, I also like relays on all high demand items, I feel all headlights should have relays not run the power through the switch like the factory did.

Sometimes I have wired stuff to the starter lug sometimes I have a remote lug buss this time the alt has a clean run to the battery, some do not like that but I do.

Most factory clutch fans move way more air than the best electric fans not a shock to me they did and do still do in some cases work well at idle with AC on, but I have seen many that when stuck in our hot fl traffic the AC isn't as cool as it should be, I lost count how many small electric fans I have added to the front of the condenser to help, it is super hot here.

People will always question the benefits of something new and or more expensive, great example is the Dewitts radiator debates here that will never end, is a dewitts aluminum radiator better than the radiators that came stock in 68-82's yes, with the exception of possibly those heavy duty factory cooling systems that I have limited info on.
Is a dewitts worth the money they cost? I haven't found one person yet that says no.
So why not mate that with a better fan?

Significant increased added benefit? well the dual 11 spals do work so perhaps it would be a hard sale.
I did a quick Google and Ebay hunt one problem is people sell the dual 11" fans calling them real spal when they are a cheap crap import for 100.00, if you want spal buy real spal.
Real spals dual 11 seem to be about 25-50 cheaper than the dual 12 derale I use, like I said I wanted the most/best I could get, the fact that my fan choice covers more radiator and moves more air in and of itself makes it better than a unit that doesn't cover as much and moves less air, that is just common sense, it doesn't make it something everyone will want or need but I wanted it and went for it.
The next fellow will have to make up his own mind about it, if the step up to the next level is worth it to him.

Thanks for the respect in understanding that I wanted more....normally I play it cheap but I was already into this cooling system thing rather deeply.
My OCD would have driven me nuts had I settled for the smaller spal set up.

I guess using relays rather than a computer stepped fan controller is the one thing I did do within my budget.

DUB

In my situation (as many may know)...Where I deal with Corvettes with a factory copper/brass radiator with and without fan clutches or electric fans... and A/C or no A/C...or aluminum radiator with electric fans or stock fan...basically any imaginable combination.

I am NOT married to a specific anything. Meaning I do not force a customer to put in an aluminum radiator...'just beacsue'. This is because I have to get what they give me that needs servicing/repair to work and I do. But what I am finding sometimes is that the parts offered in some of the repairs seem to be crappier and crappier and not correct.

I do have some areas of the car where I am REALLY strict on what is used.

DUB

John 65

Here ya go: https://www.summitracing.com/parts/spu-ix-195ts

On at 195 off at 175. Works great.

brent319

I guess I am confused. If there is a never ending debate about weather Dewitts is worth the extra money, but not one person has said it is not worth the extra money, then that is really not much of a debate, now is it?

I chose to spend my "toad pelts" on other things and have had no problem at all. I have driven thousands of miles over the last three summers. I have hammered on it. I have also sat in stupid hot stop and go traffic for three hours straight on power tour in Wisconsin. Not a problem.
Yes, I know I am not running a big block, but that's the point. We all have different cooling needs and budgets and for me anyway it was not worth the extra money.
I am glad you are happy with your setup and can say it is the best based on all the miles you have used it.

DUB

I know how you feel. After a hard day...I wonder sometimes if this is worth it or not.

I can write that there are members of this fourm who choose to do things there own way and do not worry about what others may think.

And then you have members who try to find a way to do it differently and NOT buy what is given as a package or what is commonly used by others. Which is fine also.

Some are worried about money and how much it costs...and do everything in their power to do it as inexpensively as possible. They may spend hours searching for somehting and save a few dollars....and if they feel they have 'gotten over on the system'...and saved a few dollars and spent that time....well that time was well worth it.

So knowing that there are so many personalities on this forum...it is hard to tell when these personalities collide.

I have found that if I comment on what I use or what I do or how I do it to try to help someone....there will often times be a member or two that just has to question what I wrote...which is fine...but often times they may forget that I work on these Corvetes every day...and have seen countless scenarios of a problem....and all I am doing is passing that along.....because I am NOT just a guy giving his opinion on what his car is doing or had done and that is all I have to draw from for 'experiences'....and I am NOT writing that that is a bad thing either.

AS a matter of FACT.,..I HOPE members comment on what they have experienced....because it may just help me.

DUB