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1994 K3500 extended cab dually

Duvall said:
Nice choice in buttons. Looks like a squeeze to get them both on that little plate. Some careful drilling there.

I'm guessing that the LED is connected to the same side of the relay as the fan, or fan clutch in this case?

If you push the button while the temp controller is already commanding the fan on, will the fan remain on if the temp controller drops out?
Click to expand...

Yeah there wasn’t any room to spare to fit both of those nuts side by side in there (that’s what he said..).

The LED in the switch is running parallel to the fan clutch.

The push button and the temp controller are also running parallel so as long as there is a signal from one the fan will turn on. The fan controller for the fan clutch has all the wiring to do this built-in, but for the trans cooler fan since I’m making my own controller using a relay I’m incorporating diodes in each leg of the circuit so they can’t back-feed.
 
ak diesel driver said:
Can you draw up a wiring diagram? This is exactly what I want to do
Click to expand...

Here's a screen shot of the schematic info on the superbrightleds.com website:

1619106640440.png

And here's a rough schematic for how I wired the switch and the fan controller together. It's pretty simple. I'm using the same fan controller that you used, so this should be exact for you. The Normally Closed contacts for the switch aren't used in this case, but you can see in the examples above how they have shown using them for specific cases.

switch diagram.jpg
 
ak diesel driver said:
Awesome thank you. So one other ? If I want to use the AC portion of my fan controller where's the best place to tap into on the ac wiring?
Click to expand...

Hmmm, I think that's a bit more of a philosophical question. I know that topic was discussed a little in your fan clutch thread. Personally, I can't think of a good trigger for the fan based on the existing AC system. I wouldn't want the fan to run just any time I have the AC on, and I also don't want it to cycle with the compressor clutch, so that takes care of the easy inputs. Ferm or War Wagon mentioned a high pressure switch, but I'm not sure when exactly that would trigger the fan to switch on, but I feel like while that would be helpful it may be too late at that point. I feel like the ideal input would be a combination input that took into account ambient temperature and vehicle speed when the air conditioning is switched on, so the fan would be locked when vehicle speed is low and it's hot outside. Right now that's beyond my capabilities, but maybe someday I'll dig into it further.
 
Ok, this is where you hear WarWagon YELLING (especially at dodge) about a trinary switch.

I am typing this out incase video links die in future, but video is far better description than mine.
skip my writing and watch the videos if they still work.

Gmt400 owners and Hummer owners, your ac system right now has a binary. Binary switch has 2 wires. Binary cuts off compressor if pressure is too low, or too high. 2 functions hence BI -nary.
A trinary switch has 4 wires. TRI-nary switch does the same two features, but also a third feature: when head pressure is high enough to need the condensor to cool off, it will turn on an electric fan. 2 of the wires do same job as binary. The other two wires are for the head pressure control.

So the fan will not come on whenever ac is on... it comes on when ac is on AND head pressure is climbing enough to need the fan.
It is kinda like a temperature switch for the ac refrigerant but pressure translates to temperature for this need.

you just remove your binary switch, and connect the two black wires in its place. Then connect one blue wire to chassis (battery) ground. Then connect the other blue wire to the EDIT. Ac control switch.

Off roaders who will submerge any part of the fan in water, add a switch between battery power to relay,so you can TEMPORARILY shut off the fan from working while fording deep water to keep from damaging the fan or radiator.


 
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So if I'm sitting idling and it helps the air to be cooler when I flip my fan on it's because of head pressure? Literally the only time I need the fan
 
ak diesel driver said:
So if I'm sitting idling and it helps the air to be cooler when I flip my fan on it's because of head pressure? Literally the only time I need the fan
Click to expand...

Right. I haven’t watched the videos yet, but going off of what Will wrote I feel like I get it. For Will and War Wagon (desert dwellers), they’re trying to keep their system from shutting off due to the system reaching perilous pressures. Whereas I (and I think you, Les), are more interested in making the AC cooler by keeping air moving across the condenser when it would help. This is where it gets philosophical. The head pressure sounds like an important thing for sure and something I may do anyway, but it doesn’t help optimizing the AC in low speed/high ambient conditions, which is what I would want to improve.
 
To the ac system- yes.
When ac compressor is pumping snd cold air coming out the vents, all is good. But when the refrigerant gets too much heat in it,( it can’t shed enough heat out the condenser) the pressure is higher. At the point it would help to lower the pressure, the trinary switch will engage the fan. This cools the condenser (and refrigerant inside it) and now cooler refrigerant goes to your evaporator inside the cab- making the air you feel colder.
 
So whenever you have nice cold air blowing on you and the condenser is working well enough without the fan, the head pressure will stay lower. That means the fan won’t come on.
So it isn’t on when not needed.
 
n8in8or said:
Right. I haven’t watched the videos yet, but going off of what Will wrote I feel like I get it. For Will and War Wagon (desert dwellers), they’re trying to keep their system from shutting off due to the system reaching perilous pressures. Whereas I (and I think you, Les), are more interested in making the AC cooler by keeping air moving across the condenser when it would help. This is where it gets philosophical. The head pressure sounds like an important thing for sure and something I may do anyway, but it doesn’t help optimizing the AC in low speed/high ambient conditions, which is what I would want to improve.
Click to expand...

How about a micro switch on the throttle linkage and a timer?

Let off the throttle and come to idle and the linkage hits the micro switch. Timer starts for a preset time, then times out and starts the fan until you bring the truck back off of idle. The timer could be optional of course.

I guess the DS4 trucks would have to use a switch on the pedal or something. They don't have throttle lever, right?
 
Twisted Steel Performance said:
My system uses a trinary switch taped into the ac line right off the compressor ...

There are different temp/pressure switchs as well...
Click to expand...
I could see that working if you have the option of choosing a different set point. Variable would be ideal, but I doubt that exists.

I have no doubt that a trinary switch improves the function overall, I just can’t equate in my head what pressure is appropriate to make it come on and have the AC feel like I want. I’m sure that number could be found, but I don’t know what that number is without some testing.
 
Twisted Steel Performance said:
My system uses a trinary switch taped into the ac line right off the compressor ...

There are different temp/pressure switchs as well...
Click to expand...
Yours is using the hmmwv fan clutch and controlling clutch engagement with it right? Same concept as these guys using it to control the electric viscous fan clutch.

Yes there is are different pressure switches available. The pressure the guy in the video says is based on vintage air systems. A person could really dig into their system range and learn when it goes from cooling to super cooling and get a switch to activate exactly at that traditional point for peak performance and peak mpg. But the one he recommends will do descent for any 134a system. FAR better than none at all, obviously. But if someone wanted maximum ac at the expense of engine power loss and mpg loss- then yes ac on turns on fan would work. But for such a simple modification and low cost- well worth it imo.

To do what N8in8or is saying- to come on by the interior temperature- just another fan controller. That probe works inside the cabin just like it will in the coolant.
Idk if they make adjustable trinary switches. Would be cool (pun intended).
 
Will L. said:
Yours is using the hmmwv fan clutch and controlling clutch engagement with it right? Same concept as these guys using it to control the electric viscous fan clutch.

Yes there is are different pressure switches available. The pressure the guy in the video says is based on vintage air systems. A person could really dig into their system range and learn when it goes from cooling to super cooling and get a switch to activate exactly at that traditional point for peak performance and peak mpg. But the one he recommends will do descent for any 134a system. FAR better than none at all, obviously. But if someone wanted maximum ac at the expense of engine power loss and mpg loss- then yes ac on turns on fan would work. But for such a simple modification and low cost- well worth it imo.

To do what N8in8or is saying- to come on by the interior temperature- just another fan controller. That probe works inside the cabin just like it will in the coolant.
Idk if they make adjustable trinary switches. Would be cool (pun intended).
Click to expand...

Ok Will, you’ve convinced me this is a good idea and something to explore. One correction though: I was wanting to trigger off of outside ambient air temp, not interior. If my AC is running when it’s cool out like during defog/defrost, I imagine there’s no need for the fan to run then. The more I read what you’re saying and think about it, I think this is probably a feasible and easy way to skin that cat.
 
If the ac system doesn't reach the trinary switch pressures it won't trigger the fan, the correct ac pressures should be easy enough to find... maybe @THEFERMANATOR could be of some help.... I don't remember what switch is in mine ...
 
The pressure is directed correlated to its temperature. It doesn’t matter if you are trying to use it for humidity removal or to cool an area. The idea of the trinary switch engaging by pressure can be thought of as the r134a hitting a certain temperature. Because as the temperature increases- that increase the pressure. Its just like coolant in the radiator. Engine heats up the coolant, the more heat it builds more pressure.
So you really can think of it as the ect sensor for the fan but in the a/c system.

I don’t want anyone to think actually using a second fan controller just hanging in the air is a good idea. It “could” work, (wether in the cab or outside) but would be horrible at it. I was saying that kinda in jest. Then realized y’all wouldn’t get how I meant it after reading the last post and re-reading what I wrote.

Yes an adjustable trinary switch really would be ideal to tune the best efficiency. But I doubt one exists.

Using controls with the engine throttle or speedometer wouldn’t work. The engine rpm is radically different from what is happening in the ac. Same for speed. Yes, freeway travel should have enough air flow to have ac work without a fan. But then again, same applies for radiator and engine heat. Yet how many 6.5 NEED the fan on going down the hiway. So if the engine radiator needs the fan because it isn’t getting enough air at 55 mph, that condenser isn’t working to well the. Either. Even so, 55 mph on a humid or even rainy day is gonna be way different from 55 mph on a dry day.

There are engineers for hvac systems that probably could do some serious math and determine the exact pressure the trinary switch is that would be best. That stuff is way above my pay grade.
 
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