20 amp fans pulling 24.8?

[MoparManicMechanic]

Hey,

I have a pair of 12" flex-i-lite fans that are secified to pull 20 amps. Well they cooked a fuse to the point that it was burnt to a crisp. It was one of those small 1/2" square kind- 30Amp. But it melted the holder to it. I called flex-i-lite and they said to put a Maxi fuse, the larger one 30Amp in it. I am waiting for it, I ordered it, but I am wondering why the fans are pulling 12.38 amps each, almost to a hundreth of an amp. They are supposed to pull 10 each. I am wondering, would it cause it to pull more amps because it is pulling air through a 4 core radiator or is that not a factor?  Seems to me they are both pulling equally as hard so it would make sense that they are both pulling almost identical amps, but 2.38 more than they are supposed to, or are specified to? I just don't want to burn something up... Anyone have any experenice with electric fans pulling more amps than they were specified to?



Bob
70 Gold Duster/360

[NYrr496]

What guage wire you got running them?   Are you using relays?   

If you're using small wire, you're using amperage just heating up the wire. 

[MoparManicMechanic]

12 Gauge is what I was using between the starter relay and the control box all an all the way to both fans... Should I go to 10 gauge between the positive source, which is the starter relay, and the control box which is the location where I have the fuse, between these two. The 12 gauge wire isn't getting hot, but I tried putting a glass fuse between these two sources and it heated up where the ends of the fuse meet the ends of the wire in the holder.  It is one of those cylindrical type holders, and the heat was right were the ends of the glass fuse are, on both ends after running them for 5 minutes.

It has been suggested to solder the connectors on each end of the wire, use 10 gauge, and a 30 amp Maxi fuse. Is there another relay of which I don't know about that could help this situation?

Bob
70 Gold Duster

[NYrr496]

I meant to run them with a relay.  That way, the load lead is short as possible and not going through the switch. 
12 Ga should be plenty.  I was just hoping you weren't running 14 or 16. 
The two fans are in parallel, right?

[68_Val_Sedan]

use a 20 amp fuses to feed each, with #12  on their own relay .... tie the inputs for the relay together.   As a general rule you do not want to run a constant draw circuit like  a fan at more the 66 % of its capacity ... so that would translate to  20 amp draw for a 30 amp fuse or 14 amps for a 20 amp fuse ... it will greatly reduce the heating of connections you are using ...

[MoparManicMechanic]

I'm not sure how I could put a relay for each fan. I'm not sure how to set that up with the set up the fans came with. I have one control box with the main power coming off of the starter relay which is pulling the 24.8 amps with a 30 amp fuse and 12 gauge wire. If feeds a parallel circuit to two separate leads that power each fan separately. And the grounds go from each fan, to the control box, from the control box to a wire that goes to the negative battery terminal, which is not getting hot/12 gauge wire. Also, the main power lead is only 9" long so I don't think it is too long of wire there. The leads to the fans are approx 2-1/2 feet long, if that 12 gauge also. I know someone who is not at work today that I can ask tomorrow how to set it up to have two separate power sources with two separate relays and fuses. I will get back with you on that. I may need two separate control boxes... The set up has a probe in the radiator that reads radiator temp which turns on the fans. I also have a manual switch.

So your saying it is okay for the fans to pull that much amperage when they are spec.ed at 10 each that are pulling 12.38 each?

Thanks,
Bob
70 Gold Duster

[68_Val_Sedan]

yes they can pull more amps than rated depending on how much air they are moving.   25% over or under is not uncommon ... the lower the voltage @ the fans themsleves will cause more amperage to be drawn. 

[flyboy01]

I would run 10ga for both fans, or 12 ga for each fan, I agree on the fuse too, you should run a maxi fuse. I would not run a breaker, just carry a spare fuse in the glovebox. When i unstalled a viper dual fan in my buddy's ram, I ran an 8ga wire for each fan runn off of a dual output fuse holder and a 60a maxi fuse, then we had a short section of 6a run straight to the battery. Both leads off the fuse ran to a pair of 50a breakers to control each fan. I set it up so a thermal switch controlled on/of for the main fan, then a manual switch inside the cab would over-ride the thermal and turn both fans on regardless of the thermal, we also wired in a light to let him know when the fans were on. This setup has worked for almost two years without a problem. SOmetimes it pays to go bigger than needed with wiring, it is more reliable when the components draw less than what they were rated for and stay cooler.

[MoparManicMechanic]

I will check the voltage in the morning to see if it is less than 12-13. I will go ahead and run a 10ga from the starter relay to the control box with a maxi fuse. I think I may have to split the circuits up since it is not a good idea to run a fuse constantly at more than 66% of it's rating. I will see what I can do in the morning... Hope that maxi fuse assembly I got ordered comes in tomorrow...

Thanks for your input...
Bob,
70 Gold Duster

[68_Val_Sedan]

any time .... make sure to let us know how it works out for you ...

[NYrr496]

You do have to split the feeds.  You said you have one tap off the starter relay that splits into two, right? 

[abqdart]

I would wire in a relay. Go to the junk yard and pull one out along with its holder. It is really simple to wire in a relay AND your components will love you for it!

[NYrr496]

 

[MoparManicMechanic]

Ya, the control box is suppose to split the circuit into two leads, I don't know what they have inside the control box, if there is two small relays or what.

The box is about an inch and a half deep by 3 inches wide by about 4-1/2 to 5 inches long. I can call the mfg and see if they have two relays in there. But ya the way it is set up is that it pulls one line off the starter relay and right now it is trying to pull almost 25 amps!

While your here, let me ask you this... If I use a thicker wire going from the control box to the motors, 10Ga instead of 12Ga would that increase the voltage getting to the motors? That may be the problem. I am using the 12Ga that came with the set up, but the mfg says that the small 1/2 inch fuse they sell them with is insufficient to carry that much of a load.

I am wondering cause '68 mentioned that if the motors aren't getting sufficient voltage then the amperage draw would go up. If they underestimated the fuse required, they may have underestimated the Gauge of wire needed too. Just a guess...

Thanks,
Bob
70 Gold Duster

[NYrr496]

Maybe.  I'd be more inclined to do away with the control box and just relay up each fan.  Look at Painless Wiring's website.  They sell nice weatherproof relay kits and temp probes.  Even if you don't buy their stuff, you'll get an idea for how it should be wired up.  If I had the SLIGHTEST idea how to post pictures, I'd draw you up a diagram.

[68_Val_Sedan]

here you are.  I found these pics online   The 1st picture is how a relay works.   the second show how to wire one.   hook the #87 terminal to the fan and the #85 terminal to the temp probe.  and the #86 to the key switch.  if you want to add a manual switch,  hook one side of the toggle to ground, and the other side to the #85 terminal  along with the temp probe   

[MoparManicMechanic]

Thanks for the diagram '68!!!

Any idea where I can get a temp prob with an adjustable switch to turn them on?

Thanks again...
Bob
70 Gold Duster

[68_Val_Sedan]

I thought you already had a temp probe in the rad ??

[NYrr496]

Painless has all that stuff. 
http://www.painlessperformance.com/webcatalog/plarge/30104.jpg

[MoparManicMechanic]

I suppose I could use the control box with the temp probe I have now using only a small current to tell the two relays to kick in the full current. That would work.

Should I pull the main power to the fans from the front side of the starter relay instead of the rear? That may be where the voltage is dropping off if anywhere. Sorry, I'm not much on electrical stuff. I have dyslexia and crossed wires a couple times so I usually don't do electrical work, but if I am really careful I can do okay at it. I never took it in school like I did mechanics, way back in the early 80's. I have pretty much maintained my stock mopars and not fooling with the electrical system, just kept up on the mechanical stuff, which is easy compared to the electrical aspects of any car. I got out of mechanics in the late 80's and took up mechanical drafting, so my knowledge in electricity is limited. I appreciate your help. That goes for all of you, we'll get this thing working one way or another...

Bob

[NYrr496]

Do you have a meter?  It'll help a lot towards learning what works and what won't. 

[MoparManicMechanic]

Yes, I have a volt meter and a clamp amp meter.

I am going to go out and check what the voltage is when the fans are running at the control box outlet at idle then at 1400 rpm.

I am thinking that maybe they were pulling 24+ amps because the engine was at idle and that is where the lower voltage was coming from.

I can set the idle up some so that it generates more electricity to power the fans, then I will run another amp test to see what they are pulling with the engine at say 1400 rpm vs 800 rpm. I will get right back with you on this...

Bob

[MoparManicMechanic]

Oh Boy!

I set the idle screw up to about 14-1500 rpm and turned on the fans, they pulled 29.3 amps! Something ain't right somewhere. I have to wait till it cools down so the I can manually turn them on and off to test them again with the engine running. I am going to see if one motor is pulling more than the other, that would indicate a bad motor. If they are pulling 15amps equally, I can see how I am burning fuses! The charging system is at 15 volts at 14-1500 rpm.

Bob

[68_Val_Sedan]

OK slow down here ... I have few questions so we can trash this magic control box.

The temp probe  .... how many wires get hooked to it ?

The fans ... do both the +12V and ground wires go to the box ?

Can you get 2 relays  and 2 20 amp fuse holders ?

[MoparManicMechanic]

Hey '68,

It is a monster control box. The main power goes into it, it has a line going to and from the manual switch, one lead going to both not two wires, one wire for both fans, and one ground coming from both fans. The wires going to the fans split in two  between the control box and the fan motors, close to the fan motors, about 8" away from the motors.  And one wire going to the battery/ground. The temp probe has a tube that also goes into the control box which has a dial on it with no numbers, I just watched the engine temp and adjusted them to come on at about 190 degrees.

I would have to come up with a new probe with temp switch, and set up some relays in-between the switch and the fans. I think at this point it would be best for me to hire someone to do the job because I know so little about electricity I would probably fry something : )  But I get the idea. And I can get the temp switch from painless and the relays from the parts store, so I should be able to find someone that can hook me up a system that can handle the draw of the fans. But they are pulling almost 30 amps, that is why it cooked the fuse apparently. As long as they are pulling equal amounts of amperage, I would say I just need to beef up the switch, wires, and put two relays one for each fan.

Man, now my head is spinning, I hope I got that all down right. 

But I think your right, I would do better with a custom control system rather than a 10 in 1 master control box...


Bob
70 Gold Duster

[WildCat]

I have a Be Cool Radiator and switched fans to one a little thinner so I could center it in the radiator instead of offset. It was OK for the 1st 250 miles but took it out on the interstate and was cruising at 3100 RPM and when I got to the car show I noticed my fan was not working.

I too burnt the fuse holder. It should have blown the fuse, but it melted the holder to the point the wires were exposed. It didn't affect the wires from the connectors back, just melted the black rubber holder.

I have relays to turn the fan on when the temp probe says for the fan to come on plus one to turn it on when the AC is on.

I have no idea why this happened. I have a single fan that is new. Once I get a few more thengs done to it I plan on replacing the fuse that I reinstalled with a curciut breaker and wire with 10 gauge wire, but I don't want to have it so it burns the whole car down, so I also need to find the root cause of this.

[MoparManicMechanic]

Hey WildCat,

Sounds like we have the same identical problem. My Flex-i-lite fans are supposed to only pull 20 amps but are pulling just under 30! I suppose that is the cause for mine. See what yours are pulling when you speed the idle up to around 1500 rpm, then run an amp meter to see what the fan is drawing. If it is like mine, it may have a bad motor. I called the mfg and they are sending me new motors, but if they also pull 30 amps I suppose I will just go back to the old mechanical fan and shroud. A while back I found the reason why my engine was overheating to begin with. "Somebody", who "helped" me put the engine together didn't tighten a couple of bolts on the passenger side of the timing chain cover, the two lower ones, so that is why I couldn't keep her cool. That is what I bought the electric fans for in the first place because the darn thing would just creep up the temp gauge. The leak was so slow that it would only drip about once every 2-3 seconds, but as you know any pressure leak is enough to cause overheating. So long story short, if the new motors don't fix the problem, then I will just go with the stone age, but reliable mechanical fan off the water pump.  : )

Bob

[abqdart]

3.8 liter Sable /Taurus or Lincoln MK8....... Those fans seem to do the trick.

[guzzimike]

I have dual Flex-A-Lite slim fit fans on my 383.

I used this Relay/controller kit form Derale.

http://www.derale.com/adjust-fan-controller.html

It's been in place working great for two years of daily driving in SoCal ( Hot Summers )