Alright, you guys helped address my concerns with the ac. Now I installed a pcm by tuned by frost, he has been super helpful. Before I bother him again I wanna see what you guys think.

I wired up the fans with 3 relays, in series for low and parallel for high speed. And I informed frost I was doing so.

With the harness hooked up I can command the lows on with a tech 2, and they work. But when I command high speed I only get the right fan in high speed.

The problem is the pcm isn't commanding relay #1 for the left fan. It commands #2&3. So if the left hand had power to it it would work at high speed also.

He flashed the pcm as a gto which usually uses just two relay fan set up. Since he reflashed for 3 relays is that why it isn't working when I command relay #2 with the scanner for high speed it isn't command relay #1 as well? Will it command both when the temp gets to 208?

 

You can usually run A/C without hooking it up to the PCM, the IAC will compensate for the extra load on the engine. But if you want to hook it up like factory, then it will depend on what year your engine and PCM are.

 

The motor is a 04 suburban 5.4. Refreshed, flat top Pistons, stock heads and a mild cam. The wire harness has blue green connectors and the Pam is being flashed based off a 04 gto tune

 

I've been running 2 setups (Vintage & Classic Air) for years with the trinary switch control, no ecu. No issues.

 

So when compressor and cooling fans kick in together - ecu catches it and maintains stable idle? I'm about to embark on LS3/08 Corvette ecu and Classic Auto Air traditional r134 set up.

 

I'm running an 02 LQ9 and 05 L59, both DBW. The ecu idle control doesn't seem to have any issues with maintaining a stable idle when the compressor kicks on and off.

 

garys_68, which system do you prefer? (VA or Classic)

 

I've installed Vintage Air (68 corvette) and Classic Auto Air (72 Olds 442). On my 72 442 I went with Classic Auto Air universal kit, partially because Vintage Air had not put out their Olds kit yet.
The Vintage air is a pretty hi tech unit. It uses computers to interpret the control positions, heater control valve is electric rather than vacuum, stepper motors control the air doors, even the fan speed is controlled by pulse width modulation rather than the old resistor pack.
I've had 3 issues with the VA unit in 5 years. The heater control valve stuck and had to be replaced. The fan speed control occasionally doesn't stay on high (not yet resolved). The controls had to be recalibrated for proper air door operation. I had to remove the computer and send it back for some repairs too.
The Classic Auto Air is infinitely more simple, which is why I chose it for a custom install requiring modifications. Both the heat and air doors are controlled by cables. The unit is slightly smaller than the VA. The one drawback is that there is no separation between the floor heat ports and defrost ports. It was VERY easy to modify the Olds controls to operate the heat and air door controls (not sure why they never came out with an Olds kit, as simple as it was). Due to it's simplicity, it was easy to make mods that fit what I want. I drove all summer in 100 degree heat and it worked great! The classic Auto kit was a couple hundred dollars cheaper too and gave a discount on the Kwik LS AC bracket.
Both companies were great to work with. I had a lot of mods (trinary switch, serpenrtine compressor belt pulley, etc) and both companies worked with me and took a lot of tech calls.
So they each have their advantages.

 

Thanks for the mini-hijack guys -- makes me feel better about how this will perform. I've been impressed with tech support and the installation process on the CAA system so far. As garys68 alluded to, it's sure nice to have (on mine) everything electronically controlled --- no more cables or vacuum operated stuff. We'll see how it works this summer!

 

Thanks for all the good info. I was hoping I could just let the ac work off the factory controls and the iac would keep the idle in check. Good news!

 

As long as you have a stock cam it really won`t matter if you let the PCM know when the A/C is on. If you move up to a big cam that has a poor idle to begin with you will need to keep the PCM in the loop.

 

One more reason I'm glad I made the choice to leave the cam alone.

 

I changed my original post to address a new problem

 

can you show your wiring diagram?

 

I based it off of this.

 

even in the diagram I don't see how the left fan would get power to it in high speed. There is nothing exciting that relay. Unless when the pcm sees 208*f it grounds both pins 33 and 42.

Pin 33 has power when i command relay #2 with tech2. But pin 42 does not. Is this just kind of a glitch when using tech2 to check cooling fan operation on a gto pcm. I've never had this happen when diagnosing customer cars (i.e. Suburbans, impalas....). But looking at a gto wiring diagram the fans are controlled through the bcm.

Me and frost talked about this and he provided me with a pin out. Again, only reason I am not asking him yet is I've had lots of questions already. And I'm waiting till I actually warm it up to temp and see if the fans function correctly.

 

How do the fans themselves enable low speed? Is there a high speed and low speed terminal on the fans?

 

Low speed is achieved by running the fans in series. The function of the relays switches the circuit from being in series to being in parallel. two fans in series means they turn slower than if they are in parallel, each fan has two wires going to it.

 

From what I have read on this topic, the 3 relay set up controlled by 2 PCM signals should work just the way 92 corvette explained. the middle relay switched the fans from series for low speed to parallel for high speed. At least I hope so, because I also hooked up mine that way. I don't know anything about a GTO PCM, but I was told that my f body LS1 ECM works that way. the high fan signal (33) should energize relay 2 and 3 and the low fan signal (42) should energize the left fan anytime the temps are above the programmed threshold.

 

Oh. I see / understand the circuitry now. Yes, I'd agree that in high speed, the PCM should command and energize relay #1 via the ground output to provide 12V+ to the left fan.

It sounds like a programming issue, given the tests you've collected.

Doug