svt

Just thought I'd post this for the archives. After reading all the different posts regarding the LS1 fan diagrams and correcting the inconsistencies and cleaning it up for us simple non-engineer types, oh wait I am an engineer well you know what I mean, I came up with this:

Thanks to all that posted previously, without you I could not have creatd this.

70 LS1

iTrader: (1)

That's a lot prettier than my hand drawn one I keep posting.

shifty`

iTrader: (3)

That is definitely nice. Got one for someone wanting to just do high speed all the time? I don't care about low vs high speed, and it seems to convolute the wiring a bit.

G-Body

iTrader: (4)

I can`t make nice diagrams but I can write it out.
Terminal
86 to C100 pin J
85 to switched IGN +
30 to fuse and then BAT+
87 to positive side of fans

Depending on how much current the fans draw you may have to use 2 relays to get enough amperage capacity. If you do the connections are the same except for terminal 87, connect the + side of one fan to one relay and the + side of the second fan to the second relay.

Hook the - side of the fans to a ground and your done.

shifty`

iTrader: (3)

These are 97 Iroc fans, or possibly 94-96 LT1 fans, 2x12". Are you suggesting to run one dedicated wire per relay? What gauge is suggested for the power wire Batt->Relay?

svt

thats an intersting idea, I guess you really don't need the two speed setup. If the two fans do draw 40 amps, you should probably use two bosch 30amp relays if you can find a 40 amp relay then just one would work.

Question G-Body, most of the diagrams I saw had connection 30 to "hot at all times" not ignition, I wonder, does the computer run the fans after you turn it off if its really hot? Then it would have to be wired to "hot at all times"?

High Speed Only:




After thinking about it some more, you could just run two distinct circuits, and use two 20amp fuses this is probably better:

svt

I have 2002 LS1 fans and I was planning on using the same gauge wire that is coming from the fans, its pretty thick, my guess is they are 10 gauge.


edit:

I just measured it, its 12 gauge

Jhankinson

iTrader: (1)

The computer runs the fans...but with the ignition off...so goes the fan control...so no real need to use hot at all times...thats why in mine it is on the IGN+ 10A...but really it doesnt matter...it will work the same both ways. I actually have mine wired to the BAT+ in my truck...not IGN+ and it still turns off the fans as soon as I shut the car down...so therefore I assume the computer stops the fan circuit as soon as you take away IGN+ to it. Thanks though for the point on yours based to mine...I would also like to know if there is a way to make the computer keep the fans going until it actually cools off...and not just when you turn off the engine.

J-

stealth71

iTrader: (15)

Nice diagrams. What are you using to make them?

G-Body

iTrader: (4)

Sorry about the confusion, I actually meant to put "Hot at all times", although like Jhankinson said it doesn`t really matter in the end. As far as I know the computer is not supposed to be able to turn the fans on if the IGN is off. That way it doesn`t run the fans until the battery dies and leave you stranded. When I wrote that up I was looking at the notes from my conversion because I wired my fans up as a single speed. I wired the relay into a IGN + wire since it didn`t really matter which I used. I felt better about wiring it into an IGN + wire because that way I am 100% sure that the fans cannot turn on when the car is off, that way I don`t have to worry about coming back to a dead battery and I don`t have to worry about the fans coming on when I am working under the hood. Plus wiring it to an IGN + wire means that there is one less wire that could have a possibility of shorting out when the IGN is off. Normally I like to follow the way GM wired things, but this is one of the few times when I decided that there was a better way.

G-Body

iTrader: (4)

The wire gauge that you use depends on how much power your fans need. I used 10 gauge from the battery to the relay (I used one wire from the battery and then split it into 2 to hook to the 2 relays. My fans are from a 3800 FWD GM car and draw 40amps.) I then used 12 gauge wire from the relays to the fans. I can`t remember the link to determine what gauge wire is rated for what amperage capacity, but I have it on my computer at home. When I get home I`ll post it.

jannes_z-28

That diagram is from GM's service documentation. Only thing done to it is coloring the wires.

I have it on CD from GM.

Jan

shifty`

iTrader: (3)

Here's another question for you - why are you (apparently) running two power lines to the relay, I know the one on the 30 post from battery is required to feed the 87/87a, but I assumed that the line from the PCM to 85 would be hot and 86 would be ground ed (or vice versa). Or am I just completely misunderstanding something here? Hooking up two power wires to 85 and 86 would not energize the coil, which means 87a (a = "always open/always on until 85/86 energized") would never flip to 87.

Is the ground from the relay also omitted on purpose?

Just making sure I'm understanding what's happening here. I have an excellent understanding of relays for various purposes, and I know how a 5-post works, but it's been a while since I touched one

svt

thanks but I can not take credit. I got them from a couple of other posts but when others pointed out inconsistencies in them, they unfortunately never got updated, so I just used photoshop to correct them.

svt

yeah good questions, I thought the same thing at first, then I noticed that the PCM actually grounds the relay it does not provide +12 like the fuel control wire does. I tought this was odd, thats why I thought maybe it kept the fans running after it was off like some other cars do, but that doesn't appear to be the reason.

svt

ok thanks for clarifying, I agree I'm always paranoid about running things straight to the battery for fear of it slowly draining it.

shifty`

iTrader: (3)

Last questions, I promise

Why are you using a 10A on the orange line and a 40A on the red line? the only thing that makes sense to me is that the red line is direct from battery w/a 40A fusible link to both post 30's. The orange line is a 10A from IGN fuse panel to the post 85's. I am guessing the orange line for energizing the coil is being run separately from the battery line to prevent backfeeding into the PCM and zapping it.

So, is this correct? Red line from batt to 30 post w/40A fusible link, Orange line from IGN to 85 w/10A inline fuse?

I am asking because it seems silly to run two power lines to the fans like that....but I think i'm just going to reclaim my original HEI line to supply the IGN power

svt

no problem, I pretty much learned everything I know about LS1's from other on this site and I'm happy to pass the info along.

ooooooh ok, now I see what you are saying, yes technically (on paper anyways) you could wire it one wire and it would work (again only on paper not in reality), and again you are correct if you did this your relays and pcm would be unprotected from current surges above 10 amps and you definitely don't want to do this, plus you'd problem get line noises and other bad things, yes "bad things" is a technical term

you have it right:
"So, is this correct? Red line from batt to 30 post w/40A fusible link, Orange line from IGN to 85 w/10A inline fuse?"

shifty`

iTrader: (3)

Thanks! My fan shroud didn't come in today so I'm focusing on bolting up my tank, getting fuel lines run and wrapping up what wiring is left. This info will come in mighty handy

downset71

think anybody could come up with a diagram for a set of dual fans, EACH with dual speeds?? the high speed is actually turned on with a second grnd while the first grnd is maintained along with power. (it is a 04 GTO setup). so basically, i have 6 wires.