JCurry

iTrader: (6)

I want to know what makes the idle go up when you turn the a/c on durning normal operating temps, isnt there something that goes up then.

RXciting

i'm pretty sure the BAC Valve keeps you at your set idle..
i could be wrong??

Edit: BAC Valve = Bypass Air Control Valve (just in case)

TwistedRotors

iTrader: (3)

Bac

Kenteth

thrice, bac

WAYNE88N/A

When the A/C button is pushed on, the ECU energizes the air bypass relay, which in turn energizes the air bypass solenoid valve. Since Mazda used a relay to do it, that bad boy must suck down some power. Also used when the steering is turned (steering switch makes contact) on power steering systems. May also be used for the 3k startup system, but I haven't been able to verify this yet

JCurry

iTrader: (6)

i thought it was the air control valve or something

i just cleaned the bac and did all the checks on it and it is fine but when i turn the a/c on it kills the car, and is this normal, at normal operating temp, i tap the gas up too about 2k and it goes to about 1100k and then drops to 800 and holds

WAYNE88N/A

There are several ways to check the ABS valve in the FSM- do you have the book, so I don't have to type it all (please, lol)?

Kenteth

meh

WAYNE88N/A

Don't "meh", lol...You guys are right too, I would imagine that if the ABS valve kicks in and the idle still threatens to drop below the 750 mark, the ECU will energize the BAC even further...That little guy can't handle the entire air intake load required to run that A/C compressor, though (and, you don't want it to- you'll probably burn the poor fellow out asking it to do a 100% duty cycle)...

Which reminds me...You can "see" how your BAC is doing from the ECU. I got mine to fall to about 8.5 volts (from a 14v being a 0% duty cycle) with the e-fan, headlights, and brake lights on, which translates into about a 40% duty cycle. She runs about 12v at idle, which means she's not being used much at idle with no loads, which is a good thing- it means your mechanical idle adjustments are pretty damn good...Anybody following this, or does it just sound like rambling, lol?

You can also check your air bypass relay from the ECU- you should get 12v at idle, and 0v when that A/C button is pushed (pin 1C on the S4's)

JCurry

iTrader: (6)

where is the ABS

JCurry

iTrader: (6)

so basiclly what else should i check, i just know that the idles pretty good with no loads when you turn some a/c on it tries to die, but then again sometimes it dosent do this, it actually idles the car up some, and then other times, you turn the a/c on and it idles up for a sec and then drops way up, what that mean???

JCurry

iTrader: (6)

bump

JCurry

iTrader: (6)

wayne you there

JCurry

iTrader: (6)

Bump wayne you there

WAYNE88N/A

Jeez, man, 4 bumps...On your S5, I dunno...On the S4's, it's on the left side of the dynamic chamber, with the two or three air hoses going to it. It routes air around the entire TB, from the 3/4" or so air pipe that starts at the intake elbow area, before the throttle plates...

If you don't want to get your numbers at the ECU, pull the electrical connector off of it out on the engine, and check for your 12v at the pins on the harness plug with/without the A/C on, see if there's a difference (there should be). The steps are on page 128 of the Haynes manual, although they want you to use a resistor to keep from frying something, I guess. I've never checked it the Hayne's way, I prefer to do everything at the ECU...And I gave you the numbers for that already. Since you have an S5, double check your ECU pinout for your BAC and ABSV inputs...This might help also-

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/troubleshooting-your-car-ecu-340578/

JCurry

iTrader: (6)

yeah i need to check some relays now thanx man

NZConvertible

Wayne, only the BAC valve responds to the A/C, not the ASV. The ASV only opens when the power steering relay triggers it or the hot-start assist is engaged.

WAYNE88N/A

Are you sure? I started thinking about this after I had posted (because I hate to give out bogus info), but then I remembered something way back when that convinced me that the ABSV was energized when the AC is on. I can't for the life of me find it in the book now. I think it was mainly the facts that A) the AC compressor definetly sucks down some serious engine power, therefore we needs LOTS of bypass air, B) the AC being on feeds a direct 12v input to the ECU, and what would the ECU want with this 12v input?, and C) the compressor has to need more engine power than the steering system would, I would guess, therefore it must use the ABSV also...

I can't check it out on my car (no AC for a while now), but if you say so, NZ, then it must be true

Sorry for the bad info guys...

NZConvertible

I'm completely sure.

I know this because my BAC valve is currently inoperative, and with the A/C on she's very unhappy idling...

HAILERS

****I know this because my BAC valve is currently inoperative, and with the A/C on she's very unhappy idling**** Off your duff and go out and fix it.

Wayne, when you, also, get off your duff and fix your a/c, put your meter on Duty Cycle and attach it to the bac's input wire. The duty cycle WILL pickup when the a/c is turned on, and even though not mentioned in the series four fsm, it's duty cycle will also pick up when the headlights are turned on. Air bypass solenoid is only for cold start on series four. Air supply valve is only for power steering on series four. Heavy imphasis on SERIES FOUR, not talking about any series five at all. They are a touch different.

And in response to one of your other posts...yes I was the one talking about the afm and the spring tension. Jacob did things a little different than I have in the past. Like I suggest marking the gear teeth to a non movable part before releasing the spring tension, so you can always go back to where you started in the first place.

WAYNE88N/A

Hailers, sorry to disappoint, but I doubt I'll ever "get off my duff" and reinstall the A/C system on the car. I grew up in this Houston heat, and as long as I'm moving through the air, don't need the A/C (Besides, I work in a freezing-*** room most of the time, lol)

OK guys- I got the ABSV straight now, thanks for the corrections...

I've driven with the BAC input on the meter before, Hailers, and was surprised to learn than in addition to the items you mentioned above having an affect, low speed cruising (below, say 65 mph, depending on gearing) shows it still doing a fairly low duty cycle...After a bit (minute, maybe) of steady 75 cruising, she goes dead until the next throttle transient (namely decel)...

Yes, it's always a good idea to mark things before you mess with them. But you gotta admit, he did a good job with it

What is the "air supply valve"? Is that what I'm calling the air bypass solenoid valve, or have you discovered another animal entirely?

NZConvertible

Yeah, yeah, I know. Actually fixing it is not an option, it needs to be replaced. The rubber end of the valve inside is split so it leaks air even when closed, resulting in a 1500rpm idle. It's blocked off with a bit of gasket paper with no hole in it. The search is on...

And hot start assist also.

Yep, different beast altogether. It doesn't appear to be fitted to NA's, only Turbos. So my earlier posts were probably confusing since I was thinking Turbos. The BAC definitely reacts to the A/C, but I don't know what NA's use to cope with power steering loads. There's no input from the power steering shown on the NA ECU schematic like there is for the Turbo ECU. Some NA's did have power steering right?

HAILERS

****What is the "air supply valve"? Is that what I'm calling the air bypass solenoid valve, or have you discovered another animal entirely?****

WAYNE, you need to install a turbo so you'll be on the same page as I am. (humor, ref air supply valve).

The 88fsm, unlike the 87fsm, has a page called OUTPUT DEVICES and it shows what each device does at different times. Funny thing. I always knew the air bypass valve and the bac gave large quatities of air on startup of a cold/cool engine, but never notice that the air supply valve does the same on cold/cool start ups. This should give someone that has removed these items some afterthoght if he ever has problem starting. It seems the RX likes lots of air during starting.

But then again, everyone who ever removes any of these items swears by Gott that his car idles just as solid as a rock and starts just peachy keen, never has a problem with electrical loads etc.

WAYNE88N/A

Like the A/C, Hailers, no turbos will be going on the car anytime soon, lol...

It already goes fast enough to kill me, and I'm way to old to do something ignorant and slam into something at 100 mph and leave behind a wife and three kids

It goes fast enough to thrill me, and handles like I want it to, that's all that counts

So today I learned what an air supply valve is, and that I don't need one...

JCurry

iTrader: (6)

Ok back to my prob what do i need to check now, i mean it idles fine with no loads, i mean i have no prob, its right at about 800rmps, buy as soon as i turn the a/c on it tries to die it stays at like 100 rpms(no joke),...i mean i dont think its the bac because since i cleaned it, its fine with no loads, alot better idle since clean, what do i look at next. HELP, its hot down here...