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proper dual fan operation with 04 van pcm - but without ac??
So when the ac is installed it will be a combination of vintage air type/aftermarket combined with the van denso compressor, and will be a bridge to cross when i get to it.
But what about the various speeds and cobinations that the fans run at? Will it matter that ac isn't wired in yet?
I'm thinking that fans can be controlled solely for engine temp, and somtimes a vehicles ac doesn't work.
Again it's a 04 van pcm, prob a silly question, but never thought of it
Not having a/c will not effect how the fans run. Basically you have a fan relay 1 and fan relay 2 control from the pcm. These will have to be enabled in the pcm. There are several ways to use these two controls. You need to decide how you would like your fans to run.
If you have two fans you can set the fan 1 on and off temp and have a higher on and off temp for the fan 2. Or if you've got 2 speed fans you can have both fans turn on with fan 1 control and then fan 2 control can engage the second speed.
I believe the a/c request signal simply activates fan 2 control so your fans will turn on even if engine is not to temp.
Not having a/c will not effect how the fans run. Basically you have a fan relay 1 and fan relay 2 control from the pcm. These will have to be enabled in the pcm. There are several ways to use these two controls. You need to decide how you would like your fans to run.
If you have two fans you can set the fan 1 on and off temp and have a higher on and off temp for the fan 2. Or if you've got 2 speed fans you can have both fans turn on with fan 1 control and then fan 2 control can engage the second speed.
I believe the a/c request signal simply activates fan 2 control so your fans will turn on even if engine is not to temp.
Thanks for reply!
Ok that makes sense, I ended up using lt1 camaro fans that I believe are 2 speed
Not exactly. When the pcm grounds the low speed output, the relays connect them in series so each has about 6 volts across them. That makes then run slow. When pcm commands high speed, the relay contacts change how they are powered and each gets 12 volts across both of them. The low speed pcm output must by selected AND high to make them be powered in high speed.
Not exactly. When the pcm grounds the low speed output, the relays connect them in series so each has about 6 volts across them. That makes then run slow. When pcm commands high speed, the relay contacts change how they are powered and each gets 12 volts across both of them. The low speed pcm output must by selected AND high to make them be powered in high speed.
Thanks for taking the time to explain this , think I need to learn more about how this setup will operate now, and when ac is added
Okay so the fan motors are a "single speed", and how many speeds they run is determined by how the power is directed through multiple relays, right?
I'm using a bp automotive harness that was equipped with 2 relays, witch sounds like I will only have the option of "off/on" if I keep the 2 relay set up? (witch I am fine with)
Unless you have a 3 relay fan config you will have the first relay amd fan come on HI speed at a set temperature. Then if the engine coolant temp meets the second (higher temp setting) it turns on the second fan also at HI speed.
K, got it, now I understand how they will work , thanks for explaining.
One last thing (don't shoot).....
So I've read about people using the factory van pcm to energize the fans to turn them on for the ac(in the future)
Or, could I keep the vintage air completely stand alone and still operate the the fans independently with ac controls?
Or should they not be controlled by two different sources? ?hopefully question makes sense, thanks
Based upon the multitude of differing operating systems and ac as well as fan settings in the ls1 pcm, i recommend connecting the fans to run by the pcm. Then tie in the vintage air fan control to the ls1 fan relays.
Based upon the multitude of differing operating systems and ac as well as fan settinhs in the ls1 pcm, i tecommend connecting the fans to run by the pcm. Then tie in the vuntage air fan control to the ls1 fan relays.
I am horrible with wiring, but wouldn't this possibly cause a backfeed problem, as the ecm uses a ground to activate, and doesn't the VA use a 12v+?
I am horrible with wiring, but wouldn't this possibly cause a backfeed problem, as the ecm uses a ground to activate, and doesn't the VA use a 12v+?
Depends on how its wired up. If you use a trinary switch, then it's just a switch and as long as the other side is grounded, when the switch closes it will send a ground to the fan relays. At the most you will get a code when the PCM sees a ground but didn't command it, doesn't cause a problem though and I'm pretty sure you can turn the error reporting to that so a check engine light doesn't come on.
Think I'll need to learn about the ways of this "trinary switch " you speak of.....
But seriously would you mind?
I assume that if a relay is activated by a ground to turn somthing on (fans in this case) does it know where it came frome first? (A/c or pcm?)
Am I thinking about this right?
Ok, so I researched a little, and I understand the function and purpose of the trinary switch , so this will be the route I go.
I also understand that by using the trinary switch, it will in fact set a trouble code, and that it could be tuned out.
I also understand that by incorporating a relay between the trinary switch and the fans relay/s, the trouble code will no longer be set.
.......ok here it goes....
What I am having trouble processing is , what's the difference between the ground coming directly from the trinary switch to the fans relay/s, vs. Coming from trinary switch, then to a relay , then to fans relay/s??
Also, would it be wise to have both fans turn on when a/c is on?
I dont think adding another relay to it will keep it from setting a code. It still would be adding a ground signal that the PCM didnt send and that's what sets the code. You might be able to keep it from happening by putting in a diode, but it's just simpler to just tune it out.
As for one or two fans, that depends on how hard youre taxing the A/C unit, but generally the more airflow you have across the condenser the better. If it's that slick black Cadillac (thats a Quiet Riot song from the eighties that i always think of when i think black Cadillac ) youre trying to cool in the Florida heat, then you're going to want both fans on.
I'm no electrical guy by any means, total learn as I go. The relay thing was something a couple of guys had done on the 67-72 chevy truck forum, they said it worked,
This was their diagram
Nova, since you said "diode", I just learned what they do and that sounds like a great idea. Could you recommend what "size" or "capacity" I should use?
If it's simply "tuned out" would there be any other trouble codes I would be disabling that I should want?
And ohyea, it's the caddy! Funny thing is, I ride with all the windows down -all the time
However even with windows down, it still gets a little toasty sitting in traffic, so I will still have all windows down, and ac on=)....and then there is the rain, windows up=(
05-24-2016, 01:06 PM
proper dual fan operation with 04 van pcm - but without ac?? 
) youre trying to cool in the Florida heat, then you're going to want both fans on. 
