You have a point there CFI-EFI. toggle both switches for max cooling. Toogle one for when the vette just needs a light cooling. My guess, is Ole' CC wants max cooling at the flip of a switch. However this could be accompished by a sing pole, single throw switch. Providing it would hold the current. Which in this case would be around 30 amps, barring the two fan on from stop bump. Lot of current for a millisecond or so. Usually this is taken into account by the manufacturer (surge current). You just never know...

 

Where do you get 30 amps? You are only switching the coil (primary side) of the solenoid. On my car, that is protected by a 3 amp fuse. Two fan relays? One switch? A 10 amp switch is plenty.

I just don't get all these fan wiring modifications. Especially the dual speed and the series/parallel wiring. I have a 23 year old worn out engine, in a 23 year old worn out car, that has a 23 year old radiator. My only fan kicks on at 205°. It shuts off at 195°. Under normal driving conditions, the fan never comes on. If the car sits and idles all day long, it cycles from about 208° to 210° on the hottest of days, to 195° and then starts over again. I have a 180° thermostat, and I admit that all of this is really too cool. Ideally, all the temps I named above should be bumped up 10°. A 195° stat, with the fan on at 215° and off at 205°. I DO have a manual fan switch, but I never use it unless I'm working on the car (I can defeat the thermal fan "On") or at the track, cooling it between rounds.

RACE ON!!!

 

DPDT switches are more common, at least at radioshack, so that's what I used, but you are correct, only a DPST is required.

Also, why would you want less fan when you could have more?

I'm surprised you didn't catch the other mistake yet...

 

No, on a dual fan car, a 2-pole switch is required to isolate the fan circuits from each other.

I only use the fans at the track. It allows me to make back to back runs easily. Last time out at the end of the night I made several runs back to back with about 2-3 minutes in between, and was able to get the car at the exact same temp every time. People that push and people that need to let it cool down for 2 hours before they make their first run are idiots, or lazy, if they have an electric fan and aren't taking advantage of it.

When bracket racing, I won't let the motor sit and cool too much. I'll fire it up with the fans and let it idle to that exact 184-5 temperature, where the fans and thermostat are fighting eachother. It's worked for me so far. I need to refine my shift points and burnouts a little more. I'm usually consistent within .050



Back to the subject though, do any of the 86s have dual fans? I was looking at the manual, and I couldn't find anything on a dual fan setup.

 

That'd be fun do design some wheels like that.

 

Why is double pole required at all? What would be wrong with a SPST?

I don't get the question. What did I say that proposes "less fan"? Are you talking about my proposal for dual switches for individual control? The reason I mentioned that, is for cooling between rounds, at the track, with the engine off, to save the battery. If you would only use a (the) switch(es) with the engine running, then no need.

I wasn't even looking for that one. I was just about to click on "Submit Reply", when I said to myself, "DPDT...Why"? I went back to the schematic to double check and then edited my response.

RACE ON!!!

 

Yep! your right, he is just switching the coils. Got to much on my brain right now I guess. I was thinking he was switching actual current. This simple type stuff is where I get all mixed up. I was doing this kind of wiring when I was just a young boy. I'm used to SOT's, DIP's, SOIT's, PWM's, MOSFETS (metal oxide semiconductor field effect transistors). Making circuits that energize a fan at full RPM, as a check, then making it slow down to idle with a thermister to monitor the heat in the form of resistance then speed up the fans accordingly (Yep, your right, I was charging, and discharging electrolytics, boy, I can't slip one past CFI-EFI). That was a cool project by the way. That system cooled my amps in my 74 corvette. I'll include a picture. I even built a temp gauge, and a fan tachometer. I was running 4 push, and 4 pulls. Why would I do this? because I can. Hence a proper fan system for C4 Corvettes with the single 16" fan in back, and the funny little pusher fan in front, that just gets in the way of the airflow. I am exited, and happy for you, that your car is a dream on four wheels, but there are 100's of people having cooling problems, that don't know mechanics, but are great CPA's, Dentists, Artists, and etc... You know what I mean... In the mean time, I'll keep working on this project being extremely careful not to put a switch in the main switching section of the selenoid. Did I say selenoid? ummmmm, and I meant relay... It is amazing what I can forget I was hoping CFI-EFI, could help me? I can't remember if it is trig. or calculus That you do polar to rectangular conversions?




Oh Great! Now I'm losing my hair...


Gotta admit, she sounded good. And the trophys look nice on the shelf too... Note the home made tach, and the home made temp gauge on the sink link... Well I'm no picasso, but do you like it??? In the future I will try not to make a mistake, I promise, and if by chance I do, I have CFI-EFI to remind me in his own curtious, thoughful, and proper etiquette way...

 

Anyone remember the old clutch fans? well when I built my 64..327...332 I did away with that POS and went with an aluminum flex fan, now that's what I'd like to see. It could still be ran with sensors, but I'd like to see a setup where it ran continously..robbing less HP, but at the same time bringing cool air into the engine compartment and of course the intake.

 

It can be done sir. Use a variable speed, high RPM motor, and when you adjust it to run around 3000 It will start to flatten out the blades, just like an engine would do. I think if you were going variable. You just as well put on a stock corvette fan, and control the speed via a PWM (Pulse Width Modulator). As a matter of fact one of those company, might be flex a lite, has one. No I'm not trying to be a smart ***, with the electronics talk, but that is a great way to do it. Here is a pic, I think you will enjoy... Take Care...


By the way, I have tested this fan system. Just the other day as a matter of fact. Put out about the same amount as the stock C4 main fan. I sold it to my brother for his Chevelle, and it works right nice. Perma-cool sells the unit. It is 16" in diameter. They also have an 18". I checked my shroud for fit, and it was 17". These are simple, and diverse fans. They are instant on, and instant off. A little noisy, but no more than the stock unit...

 

A single pole would require tying both fan inputs together to the normally open side of your switch. If you did this, everytime the ecm controlled the fan, the secondary would get the same ground signal. I also contemplated whether or not running the fans was bad with the engine off.

Lets say your car is really cookin at 230. You shut it off. The motor is going to keep on dumping heat into the coolant in the block, raising it to maybe 240 or more. The radiator, with 230 coolant, now with fans on, drops to lets say, 90 degrees on a cool day after 10 minutes of fan. Now, fire it up. The motor is still hot. The thermostat is still open partway from conduction and the hot intake water. You push a slug of water through that is over 100 degrees cooler, that could be a problem. Now, an electric waterpump would do the trick.

My next thought is to have an alternator cutoff at wot, people used to do this as I recall, but not anymore.. is it because it's not worth anything?

 

Here, simple dimple if you want to use only one SPST switch. Neither circuit can be back fed into the other but can find a common path to ground forward biased through diodes. These can be 1A tiny little things and the switch can be a little dinky thing too.

Even though you can get away with 1 amp diodes, 5 amp diodes are way easier to work with in an automotive environment because they have much larger legs and are less susceptible to breaking the legs off.

 

Your pretty smart on a lot of things. I'm sure you are not an electronics tech. like ALLT4 and I, but you do a great job on automobiles, and as for your switching system on your fans. My hats off to ya. I've read several of your posts, and have used the information. Keep on doing what you are doing. By my age you will be president... Thanks...

 

Next I'll post my wiring diagram and relay logic for my custom keyless entry.

 

Yes, but the dual fan info is not in the regular shop manual, it's found in the seperate electrical supplement manual that goes to it.

 

Do you happen to have this scanned? I'll pm agent86. Need the info to help out a forum member.

 

I do not. Agent 86 might though.

 

You are right. That occurred to me the second AFTER I hit the "Submit Reply" button. I was late getting to somewhere I was supposed to be, and I had to let it stand.

Like I said, I only use my fan at the track. I turn it on between the stripe and the return road cut off. When I park in my pit, I shut the engine off and leave the fan on. Initially, I spray down my radiator with water from a garden sprayer. After about 15 minutes, I start the engine, for approx 1 minute, to circulate the cooled water from the rad to the engine. Then I start the process all over again, to cool the hot water from the engine that is now in the radiator. Generally, three such cycles gets my coolant to 150° to 160°. I drive to and through the staging lanes, but I don't let the engine run unnecessarily. After my burn out, I shut off the fan and check the temp. It is most often between 170° and 175°, as I stage. Then I make the run and repeat as necessary. The more repeats, the better.

I have thought about an alternator switch as you mentioned, but I'm not sure that the power savings will compensate for the extra weight of the switch and the wiring.



I don't have "the funny little pusher fan in front", and I don't think many would refer to my car as "a dream on four wheels". But a little maintenance, goes a long way. "You know what I mean"???

RACE ON!!!

 

I'm not sure what you're trying to accomplish and you seem to know a a great deal about electronics - but you might want to consider the load on the alternator if yours is a driver (and if you're building killer stereos, you may have long since considered that). At idle, the 105 amp stocker isn't going to keep up with dual fans, full a/c (and/or a killer stereo). The last time someone slapped a meter on one, I remember 20 to 25 amps at operating temps. My own experience, having bought into it has be cooler 14 or 15 Years ago, is that two fans - or even one that doesn't cycle, will slow down once the amps aren't there and when that happens, the temps will climb. The OEM design, may be marginal, works really good when you leave it alone and simiply make sure it's a clean system; ie, clean radiator and condensor - nothing blocking air flow and no crud in the coolant or anywhere in the cooling system. There's never been a long line of Vette owners at the Dealerships complaining about overheating (well at least not when I bought mine back in '89). More alternator output doesn't always work either - Bigger is tough fit (though doable), though you have to consider that it's going to be even closer to the header and how that will effect longevity. We've had members try the ICEBERG design to get around that, (and posting pics of their fryed alternators a few months later). Frankly, if you simply want to drive it everyday, I'd get it back to the way it came from the Factory. It wasn't a design defect (well, maybe the alternator was - but the cooling system was actually ok).

 

How not to wire a fan:

On my 69 pickup, the prev owner wired the tranny cooler fan like so. 12V from battery, thin guage wire underhood, weaved through metal holes in sheetmetal and into cab, to radioshack dash switch. Otherside of dash switch runs along the same route, out to the fan terminal. The other fan terminal is a fat ground wire (red of course) with a 30A fuse on it, then grounded to the chassis.

So all the fan amps are running through the dash switch, there is no fuse protection from a short, and if the long piece of 12V wire arced, it'd burn the truck down, or spark till the battery was dead. The fuse will do nothing on the ground circuit except protect the circuit from fan overload, but then, the 12V wire would probably burn up before the fuse did.



Never ever ever run 12V through a switch if you don't have to. Always use a relay, with a switched ground (your input signal) to the coil side of the relay. The relay should be supplied with fused 12V power to two of its terminals. The last terminal (the output) serves the (+) side of whatever needs power.

That first diagram in this thread is no good.

 

Not just a little maintanance, but quite alot. Well if your me that is...
My system will draw no more in high speed mode than both fans running on the stock unit. However it will be much more efficient. Besides it will look a whole lot better as well. There will be 9 S blades ripping air through the radiator. I'll try to get some pics up soon. Like I said,"it will not switch into high unless it is very hot out". And yes, the AC will work like a charm. Actually I will just let it kick on in the low speed position, and if it is not in the low speed position, then the only other place it can be, will be in high which will cool the condensor even better, you can't loose. Your looking at roughly 10 amps at 13.5V on low speed, and roughly 25 amps at 13.5V on high speed. Don't quote me on this, as I read the current on a not so accurate amp meter. When I get the #'s, they will be dead on at 13.5 volts. Nothing left to chance. I have taken the alt. into consideration, if I hadn't, I would have to be an idiot, and I know the fans slow down as the voltage drops IxE=watts. I wouldn't even think of a bigger alt. it takes more engine power to run. See at first it was just going on my car. Then I got to reading posts, and saw a need for a good looking, but fully functional radiator cooling fan. The housing will be built out of machined 1/4" aluminum. Polished to a high luster, or for less cost, a satin unit. I also blue print the blade, very time consuming, but there is only on right way, and that is the way I do it. People that are watching me on this project around here. Think I am going way over board. But who wants that casting flash all over the edges of your blade scewing up air flow. The blade also gets a mirror polish for less drag, and greater performance. I really do think you will like it. It will be a presision unit, just like the Chevy Corvette. I'm not sure what year your vette is. If it is dual fan, you wont be able to use it, and probably will not need it. but I still think you will like it. I know I am awfully exited. Even if it just ends up on my 88.