How do I make the pusher fans more efficient?

[cee21]

Well got them wired up and set the temp controller on them and noticed that some of the air blows forward and not through the a/c condensor. I remember reading somewhere on here how some body fixed that. Also since I will be using a/c do I need to have the fans run at least at 50% or something? If so how do I achieve this?

[Richter77]

You'll need to build a shroud around the fan, forcing the air through the radiator, the A/C system should kick the fans on through the relay. When the clutch kicks in on the compressor, have the fan come on then (possibly by piggybacking off the power wire going to the clutch).

[MalcolmV8]

I wouldn't tap the a/c fan relay from the clutch because your fan will be kicking on and off with the compressor. Find a wire that goes 12 volts when a/c is on (like low pressure cut out switch) and source the a/c fan relay from there. This way your fan will be on the entire time the a/c is on as it should.

If you want the fans to be at 50% power on a/c unless additional cooling is needed you'll need a fan control module rather than a simple relay / temp sensor configuration that either has the fans on or off.

Malcolm

[cgrey8]

When you say you have a temp controller on your fans, that to me means you have a fan speed control device that literally controls fan speed, not just when the turn on and off. If that's the case, then it will probably have an in put on it that will run the fans at 50% speed when the AC is on. However if you don't have a speed controller and the fan control is either ON or OFF, then you won't have this option. DC variable speed controllers are around $100 or so. Malcolm and I both have them and I'd recommend one. However I'm not sure just anybody can buy them anymore. The guy that makes them, Brian Baskin, I think has quit selling to the general public.

As for getting more air to blow through the radiator, I noticed the same thing you did that some air blows forward below the fans. So what I did was cut myself some shrouds from roofing tin and bolted those below the fans so the gaping hole that's below the fans wouldn't allow the air to blow back forward. I also installed foam tape like what's used between camper tops and truck bed rails to seal the gap between my condenser and radiator so air wouldn't short cycle the radiator. Across the bottom, I never could get that foam to work right, so I squirted Great Stuff around that area. There are still gaps here and there that could be filled, but I've never found a reason or need to plug them since in the dead of 2 Atlanta summers now, the fans have always been able to maintain the engine temp. Note, I do have the thicker 2-core Ranger radiator. From what I've heard, a single core radiator works fine with V8 conversions as long as you have a mechanical fan & shroud. But I have no clue how well the single core would cool with electric pusher fans.

[cee21]

Hey Chris can you post a pic of your fan shrouds? That would be really helpful to me.

[cgrey8]

These aren't great pics, but if you are familiar with the front end of a Ranger, they give you an idea as to what's going on.

Like I said, I used that foam tape to make a seal between the radiator and condenser. Here's a pic of the foam tape I used. You can see it squeezed between the radiator and the front lip:

That's about 5-6 layers of that tape stacked to fill the gap. Similar stacks run down the radiator between it and the condenser. When I sat the radiator back in the perches and pulled it forward to be bolted in, it compressed the foam stack and made a seal.

These 3 pics show the sheetmetal pieces I cut from roofing tin and bolted in below the fans. Before they were there, it had 2 huge gaping holes that the air blew back forward from. Two of the pics are taken while laying on the ground facing straight up. Notice the curve/contour I cut into them to match the shape of the fans:



With these in place, no air blows forward anymore.

[cee21]

Thanks again Chris.

Malcolm, the low pressure switch, do you mean the WOT relay? Would this be the power to the relay or the wire that trips it? Just needing a little more detail.

[MalcolmV8]

No low pressure switch is right by the drier and monitors the refrigerant's pressure. If pressure drops to low it interrupts the power to the clutch relay to stop a/c from working. One side of that switch will be at 12 volts all the time when a/c is on. That's just an example, you can use pretty much any source that goes to 12 volts when a/c is on. I just wouldn't use something that cycles like the clutch.

[cee21]

I don't understand electricity to good but tell me if I got this right. If I splice into that wire, it will be 12v to both, just the amps used will go up, right? Also, the drier is the cylinder next to the a/c box?

[cgrey8]

I don't understand electricity to good but tell me if I got this right. If I splice into that wire, it will be 12v to both, just the amps used will go up, right? Also, the drier is the cylinder next to the a/c box?

That all depends on what you have and how you wire it. If you are using a DC fan speed controller, then all the 12v from the receiver/dryer low cutout switch will be is a signal telling the controller when to demand at least 50% speed from the fans. The controller won't actually require that the wire supplying that 12v signal carry the fan load. The DC controller's dedicated 12v source will do that. Even though technically the load the DC controller puts on the signal wire is there (most likely less than 1ma), it is so small and insignificant, you can pretty much assume it doesn't exist.

However if you don't have a DC controller, then you'll want to use that 12v supply as a 2nd trigger for whatever relay(s) you use to activate the fans. In that case slightly more current will be drawn from the AC trigger source because that voltage will be driving your fan relay. But relays don't require that much current (~250ma). Compared to the load of the AC clutch, the added load of the relay can also be considered insignificant, but it is far more significant than the load a DC controller would apply.

In either case, you DO NOT want the 12v coming from the dryer to be supplying the fan voltage. Even though that 12v source is coming from the AC's WOT cut-out relay, you still don't want to overload that relay. It is sized for AC clutch loads (2-5amps), not for the AC clutch AND 2 high current fans (fan inrush loads as high as 25-30amps).

[cee21]

So I could use a 30 amp relay (like the one I used for the fuel pump) and it won't affect the performance of what ever the trip wire operates. Can I do the same thing to trip the fans on with the run wire when I have the truck running? Or would I have to use another wire that is hot in run for that?

[cee21]

Was I right on my comment above?

[cgrey8]

I'm not sure I fully understand the question. But yes you can use a 30amp relay to run the fans. And as long as any triggers you have whether they be the AC or a temperature switch, only control the current going to the relay, and in turn the relay conducts the current to the fans, I think you'll be fine. What you don't want to do though is have multiple trip wires wired together on the same relay. Otherwise what you may get is back-feed up the other trigger wires which in the case of a temperature switch and AC triggering the same relay, the AC compressor could unintentionally turn on when the temperature switch turns on.

[cee21]

Well here is my big question out of all of that. Can I use the run wire to the distributor to be a trip wire for a relay so the fans will only run when it ignition is in run? Right now all I have is it wired up to the tempurtare control that is placed in the radiator. Which means the fans will be on till they cool it down even after I have shut the motor off.

[cgrey8]

Well here is my big question out of all of that. Can I use the run wire to the distributor to be a trip wire for a relay so the fans will only run when it ignition is in run? Right now all I have is it wired up to the temperate control that is placed in the radiator. Which means the fans will be on till they cool it down even after I have shut the motor off.

The way you have it is a pretty common way. However if you wanted them to operate only when the ignition AND temperature are saying to, then splice into the ignition wire going to the distributor, and feed that into your temp sensor. The other wire on the temp sensor will then go to the relay. At that point, the fans will only run when both the ignition is on to power the relay AND the temp sensor is "on" to allow the power to get to the relay. Run it like that for a while and see if it maintains. If it does, then leave it like that and don't worry about getting the AC stuff in the mix. Without a true DC speed controller, I wouldn't bother with the AC.