Well, I wired up that BAC and modified my MS board just as was said, and it doesn't do anythng to the BAC. the BAC just stays wide open full time. Thus my "idle" is over 2600. Frustrating. I can plug the BAC and get it to idle ~600 but that doesn't work until the engine is pretty warm. ANd I want it to work correctly anyways.

I put the diode from the s12c hole on the back of the board to the 3rd leg of the ztx688 transistor from the heatsink. I put in a 510ohm resistor on R19. I believe that's all the mods? My software is set up properly I believe. And I tried about 10 different combos on the software in the idle control screen and it didn't even change anything with the engine.

 

are you sure you didn't short anything?

Also, did you jumper R39?

Finally, did you make sure that you didn't overheat your ztx 688/689 when soldering?

 

Pretty sure I didn't overheat the transistor. I did not jumper R39 though. You said above that those extra instructions were unneccessary (q20, d8 removal)

 

did you read the whole post? here's the part of the post where I said to get rid of D8 etc...

 

I smoke mucho crack, sorry.

 

Ken I was looking at my MS 1 V 3.0 PCB. Pin 30 on the DB37 is the FIdle output. When I look at pin 30 where it solders onto the board (on the backside) there is a visible trace that can be followed to one leg of D8.
Now since I removed D8 I don`t see any part of the circuit I just modded attached to pin 30.
Do I need to jumper D8 since I removed the diode?
Would this explain why I get no response from the BAC when it is hooked up?

 

no, D8 goes from that pin to ground, and then there's another trace that goes over to the transistor(s).

If it's not responding, something else is wrong.

 

I think that before I start Looking for a bad transistor or some other component thats defective I would be better off making SURE all the settings in the software are correct. Since the thermowax is still in my car I don`t need the BAC for warmup idle. I`ve looked on msefi.com searching for settings that should be used in closed loop mode but have not found anything. I guess all the rotor heads are over here. Is there anyway to test the function of this circuit on the bench/with the stim/etc?

just to recap I modded the FIdle circuit as follows,

changed Q4 to the 689 transistor
removed R39 and put in jumper
removed Q20
removed D8
put a 1n4001 diode in the proto area with the banded side connected to 12vdc at s12c with jumper wire and connected the other side of the diode to the pin on Q4 farthest away from the heat sink.
installed a wire in my plug n play adapter between DB37 pin 30 and ECU plug Q2 pin.
Of the two wires connected to the BAC the blue with greenstripe goes to the FIdle output on MS and the black with white stripe have 12vdc to ground with the key on.

Have i missed anything???

 

that sounds right.

The easiest way to check on the bench is to set it to warmup only with similar settings to the FAQ...

At low temps the Fidle LED should be bright, and as you turn the coolant temp potentiometer, the Fidle LED should get dimmer.

 

I`ll give that a try and post back the results.
Thanks

 

Well Ken I tried what you suggested and I got no response. Only thing happening is the FIdle LED is on about 2-3 seconds then flashes off for a fraction of a second then right back on for 2-3 seconds.

ThenI ENABLED stim for wheel. Now I get the FIdle LED responding to the coolant temp rising and falling with no flashing. I`ll reinstall everything in the 7 and see how it does in warmup mode. Only thing is that since I have the thermowax still working how will I know if the BAC is helping anything or not. The car actually starts very well and warms up okay.

I`m thinking we just need to figure out the correct settings for the BAC in closed loop and I`ll get it worrking right.

 

don't use stim for wheel in the car! other than that, glad you figured it out.

 

No problem there, I already turned stim for wheel off and Ill double check it before reinstalling in the car.

I wish I understood more how the BAC works and also understood what the settings are for/doing etc.

There are also quite a few more settings in the current firmware than in the one in the FAQ. It sure would be nice to know what all the settings do!!!!!!!!!!!!!!!!

 

yeah, the help when you press F1 tells you what they do... I haven't had a chance to try it out or I'd just give you settings....

The BAC valve works like this:

The MS just pulses it really fast... the more on pulses in a certain amount of time, the further it opens... The stock ECU does basically the same thing as well.

 

So I finally got the board modded correctly, but still my bac would not respond, at least it wouldn't change the speed of my idle. It is full time wide open. I was wondering. I took it off and bench tested it, and it only travels about 1/16 of an inch and just opens more instead of closing. It moves the same direction no matter which way I apply the voltage. Is this a bad BAC? I got it at the junkyard after all, heh.

 

Use a DVM (digital volt meter) set to ohms and measure the resistance across the two terminals.
According to page 131 in the Haynes Manual it should be about 10.7 to 12.3 ohms. Mine was right at 12.2 - 12.3. Actually I have two of them and they both were the same. Because its a solenoid valve polarity does not matter, you can connect the wires to either teminal just don`t short them out.

BTW, sorry for hijacking your thread way back on page one, although, we both seem to have the exact same issue

 

If it's only opening and not closing, the spring inside might be worn out...

 

I got a new BAC. It looks to me like my other BAC had been taken apart and put back together wrong. There was a spring in my old BAC in between it's "closed" position and the plunger, so it couldn't close. Then to top it off, whoever took it apart loctited it back together so with the soft material it was made of, it was impossible to fix.

The new one, when I blow into the intake side of the BAC, does not allow air through when it's closed. The old one was no different between open and closed.