Is that normal ????

S5 N/A

 

Yup.

When engaged, the AC puts quite a bit of drag on an engine that's already a trifle anemic.

 

+1 thats why mine is not hooked up any more. i figure that 100 and the windows down is air conditioning enough for me!!!

 

Unless you live in Arizona, windows down no longer works for me, after 3 years i'm fixing the A/C myself

 

^^lol!!! i only live in NY so the heat thing is not that big of a problem

 

Actually, I the BAC is supposed to raise the idle when the a/c is engaged.

 

^ +1. I had problems with the BAC with a S4 n/a. Every time i turned on the a/c, the car wouldn't idle unless i gave it gas.

 

So my BAC valve is not doing the job ?
I checked the resistance and the "clink" with 12V, and it seems fine...

 

its normal, your car is slower than usual when it is on as well

 

Yup totally normal, check your BAC like everybody else said. My last RX-7 had an idle of 700-800 RPM without the A/C on, as soon as i turned it on it went down to around 450 RPM. It took a while to get used to turning off the air con at every stop/intersection, but i soon graduated to the art of stop and go traffic with my A/C....

haha, that too...

 

lol

My BAC valve is ok according to the FSM.

 

No. Your BAC valve might be good, but your car is honked up. When the A/C is turned on the rpms SHOULD increase to compensated for the A/C being on. If someone has a car that does not do that, then YOUR car is honked up also. Don't post if you don't know what the hell your talking about.

 

It was ok before I unpluged my automatic transmission CPU (auto to 5 speed swap). The idle was higher with the A/C on.

Could it be because the neutral switch of the 5 speed tranny is not wired. So the BAC valve does not compensate at the idle...

 

No. Nothing to do with the over the top/fifth gear signal.

You know the BAC isself is good. What MIGHT be bad is the signal from the ECU to the BAC. The ECU PULSES a gnd signal to the BAC to vary its opening. It's called a Duty Cycle and is measured in HZ. About 120hz give or take at idle.

Personally I thnk you should pull the BAC off the engine. It's just two nuts and a water hose. LEAVE the electrical plug on the BAC. Turn the key to ON, engine OFF. Listen and look at the BAC's diaphram and see/listen for it to vibrate. DO NOT force the diaphram open with anything at all. Ever.

Make sure the engine is hot when you do the above or at least warm. If you see the thing vibrating, then it most likely IS getting a signal from the ECU to operate. If it is not vibtrating...try moving the throttle open a bit. The BAC and see if it's now vibrating or not. It should be vibrating. And also try this. Have someone turn the key to START momentarily and see if the BAC move full open or not. It should anytime the key is to START. That shows the ECU is controling the BAC.

Here's an idea that might work although I have not done it myself. Fully warm up the engine. Then pull the SINGLE wire on the A/C compressor OFF/apart. Then while the engine is idling, turn the a/c ON. I know the compressor won't work with the wire/plug off it, BUT the ECU does not car a wit. The engine speed should go up when you turned the a/c ON. See what happens. Do this before any of the above. The BAC is fully connected up to the engine when this is to be done.

AND, what is your idle speed when the engine is fully warmed up and HOT?

 

Ok, here is my full story...

When I set my idle à 900 - 950 (very stable) and I put the AC on, it drops to 600 and then slowly comes back to 850-900.

If I put my idle around 750, it does not come back to 750... but stays lower around 650.
I know the bac valve compensate because I've unpluged it and put the A/C on... it was then below 500... and the same thing happened when I ground the green coupler near the battery.
But from what I read in this post, it does not compensate enough. (It's not dramatic, but I want my car to run perfectly)

Another thing, the BAC valve is suppose to compensate when we turn the idle adjust screw on top of the TB. When my auto tranny CPU was pluged, it did (had to ground the green coupler). Now (after the cleaning of my TB and the black plastic piece ), the BAC does not compensate for the Idle screw adjustment.

Another thing, when my car is warming up, my idle is always bouncing from 1500 to 1200 rpm. When it is warm and park(doesn't bounce anymore), I just slowely press on the gaz it stumbles when it reach the revs it supposed to go. Dropps for 400 rpm then come back. Back and forth. But the best is : when the A/C is on, it behaves ok !!!!

When I drive tough, it's flawless !


So, I'm going to verify my TPS (other post) the best I can first to see what happens (when I unplug it, my car runs better...)
Then, I'm going to try what you said with the BAC (last thing, because I don't have the gasket... so I'll have to wait to put everything back...). Gasket maker would be ok ?

Thanks for everything, and if you have any other ideas, don't hesitate !!!

Nic

 

About the BLACK PLASTIC PIECE you mention. It is possible you put it in backwards. If so then the air/vacuum ports won't go to the right places.

Try what I mentioned. PUll the single plug off the air compressor. With the car fully hot and idling at approx 750, turn the a/c to ON. The rpms should increase. It does on my car because I just did that.

 

Erased my post after I red yours.

 

I think you need to set your idle and work up from there. Engine hot. Set the tps to output one volt approx. Set the timing with a timing light. Install the initial set coupler (puts the BACs duty cycle at a fixed rate). Set the rpms to approx 750rpm. Pull the initial set coupler out and your done.

It's assumed all the vacuum hose are going where they should and there are no air leaks.

If you go to the series five FSM and its FUEL SECTION, you will find a page called RELATIONSHIP CHART. Look for BAC and the A/C switch and how they interact. Do this if for some reason you doubt the bac and a/c switch do not interact. You can also see what other items interact with the BAC.

 

The idle on my TII with the AC on is rock solid at about 800 rpm, doesn't budge at all. I only use it for days where its warm and rainy, though. Otherwise it's all about wind-blown.

 

Going to start a new post with an update.