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LS3 Cruisin'
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Discussion Starter #1
A quick snippet. For the last few years I've used dual 12" Spal Fans
Model 30102029 12" High Performance Fan - Curved Blade - Pull rated at 1328 CFM each and 14.5 Amps draw each.

They're run on a typical Camaro Series/Parallel Low/High Ground trigger relay setup controlled by the PCM.Twin fuses @ 30A and Relays rated for 50A, have not had any issues ever.

They work well, but on high they are noisy. Like very noisy. I decided to pickup one of those dual 12" 5 blade intrepid fans from rockauto a few weeks back when they got posted to the forum.

The first major difference is the hi/low aspect. Low on the SPALs is done by placing them in series, reducing voltage to 6v. Whereas the Intrepids have dual windings in each motor with both windings running at 12v. At low speed, the Intrepids move much more air than the SPAL's do. At high speed they seem to push about the same amount of air.

The other major difference is noise frequency. On high, the SPALs have a high pitched whine to them, the Intrepid fans do not get this whine. Whether it is due to blade design, the denser cage around the SPAL, or RPM difference I can't deduce but definitely the Intrepids are quieter for pushing the same amount of airflow.

On the db meter they both run at 88 +/- 0.5 db on high, no difference, but the frequency they emit is totally different, SPALS high pitched, Intrepid low pitched.

Decided to replace my SPAL setup with Intrepid for the low speed CFM boost, and the high speed noise reduction.

I intend to still run them from my Camaro relay setup, all that I will do is remove the 3rd hi/low flopper relay, and rewire the first 2 relays to just be ground triggered on the 85/86 side by the two PCM ground triggers. Repinning the RTMR panel is pretty easy.

As an aside, on my A/C system I ended up using a high pressure 7/16 high pressure trinary (doubles as high pressure cut-out safety) which trips the A/C signal wire at ~238psi, I use that wire to trip another relay which changes my input from positive to ground. The ground is then tied in to the high side fan relay trigger... A/C Comp comes on, pressure reaches ~240, high's come on. Works perfectly.

Unfortunately, try as I might, I've had no success getting the Blue/Green Savannah Van PCM to control the high fan speed based on A/C PSI. It correctly reads the PSI from the A/C High side pressure transducer I added, and it correctly reads A/C request signal and does RPM bump adjust, so I know it is getting all the data, it is just refusing to trigger highs on pressure no matter what I put in the tables. Seems to confirm the theory on other forums that the PCM firmware simply lacks the coded functionality to do it, even if the software appears to have the functionality, it just won't work. But the trinary workaround is fine... it puts the A/C system in a a hybrid auto-manual (not computer controlled, but not requiring me to flip any switches for fans etc). Comp still cycles based on low press cycling switch on accum.

Anyway just my 2c regarding differences between aftermarket fans (SPALs in this case) vs a factory setup (Intrepid).
 

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This sketch is planning stage for Intrepid fan wiring. The original setup wouldn't allow the high speed to pull in unless the low speed was engaged. I didn't see that as being necessary and set up the high speed to come on anytime the a/c was engaged. The fans could now run in 4 different modes:
1. Engine cooling with low speed.
2. Engine cooling with low speed and high speed.
3. A/C cooling.
4. Engine cooling with low speed and a/c cooling with high speed.
Thoughts?
Intrepid AC Using Trinary Switch.jpg
 

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LS3 Cruisin'
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Discussion Starter #3
Not quite... the trinary provides + on the A/C trip side, it does not provide a ground. Wiring a positive to 85 won't turn the relay on. The temp sensors it is showing assume that the sensor itself is providing a ground when the internal condition is closed, as they are typically screwed into the cylinder head and thus case grounded.

To get around that, use the 12v trinary signal on the 86 side of a third relay, 85 goes to ground, 30 would come from ground, and 87 on the third relay ties to 85 on the second relay to provide a "bypass" ground essentially to enable the 2nd yellow relay to close.

The wiring is basically how I'll run mine except instead of using a high/low temp switch I use the 0411 PCM outputs Pin 42 C1 Blue (low) Pin 33 C2 Red (high) which stays the same with a P059 PCM except Red is Green but pin remains the same. This gives you adjustable control over low/high set-point, minimum on-time, high speed cut out, etc. Much better than using an inline rad hose sensor or something.

Keep in mind that yellow and green are additive, and that either one alone will just give low speed.

Also... FWIW a 5 pin relay isn't necessary since the 87A's are never used... you can use a 4 pin relay, if you want to use micro relays for either an RTMR panel, or any kind of repurposed GM Delphi OEM panel as most of the late 90's vehicles used micro relays.
 

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Disagree. A trinary switch is merely two normally open switches in parallel, isolated from each other. The a/c switch (protecting the compressor) closes when the a/c system pressure is between 30 psi and 380 psi allowing the a/c compressor clutch to engage. The auxiliary (fan) switch closes when the pressure is over 220 psi.
 

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LS3 Cruisin'
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Discussion Starter #5
Interesting... I agree with what you said 100% no disagreement there. I'll have to go look at what I've done again. Sometimes I type these replies quick so wouldn't surprise me if I got it backward in my head when I was writing it.

Either way, what you've got will def. work, aside from like I said, you could use the PCM fan ground triggers to be able to tune control your exact high/lo temp set points vs. using a separate sensor somewhere.
 

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Thanks. My sketch of the trinary switch is too simplistic. It is closer to this, two switches controlled by a/c pressure. (The compressor switch is a little more complex than this as it has two pressure cut off points, but I can't find a good schematic.)
343629
 

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It's basically a double pole single throw switch.
 
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