Does anyone know where this connector should go on the wiring harness. It hangs near the turbo and intake manifolds. I thought maybe the BAC Valve. Any ideas?

 

Bypass Air Control Valve

 

Not. It goes to the coolant temp sender located behind the alternator in the waterpump housing. It's a good idea to have it connected since it tells the ECU when the engine is warmed-up.

 

it goes to the BAC.

 

looks like the water thermosensor connector.. behind water pump.. under alternator...

 

If it looks like a fuel injector plug but with the "key" off to one side then it is the BAC.
Of course you could tell us if you have a BAC and if its attatched.

 

Both the BAC and the Water Thermo Sensor have a green two pin plug like that.... I too am wondering if I have the two switched accidentally....

 

The water thermo sensor is already plugged in and I don't have the BAC on the car but I do have the BAC. Problem is that the BAC I have is from and S5 and the connectors are different. Is there anyway to make it work. How would you know if the two connectors were switched?

 

Water Thermosensor's two wires are Black and a Green/White. The BAC has a Black/White wire and a Blue/Green wire.

 

that fat rubber peice right on the back off the plug that has the wire coming out screams water thermo sensor.
plus the BAC or Injector plugs dont have that recess around the plug for a wire to hold them on (at least ive never seen one that hasd)

 

This is wrong.

That connector type is a typical Bosch style two pin connector with an offset tab. At least on the s4's, the water thermo sensor, the BAC and all 4 injectors share this same style connector; fat rubber piece, and wire recess w/ wire to clip them on to the sensor/injector. While the injectors are brown, the BAC and Water Thermo are nearly identical except for the wire color mentioned by satch above (Thank you by the way, will be checking to confirm I've got it right today.)

 

Gotcha. I will check to make sure that the wires are the correct color but I am almost 100% sure it is hooked up correctly.

 

Looks like the water thermo sensor based on color. My BAC is blueish not green. However you can make sure certain things are hooked up and the ecu is reading them from probing the ecu plugs also.

 

If it does turn out to be the BAC the connectors are different between s4 and s5 aren't they? If so is there anyway I could hook up the s5 BAC with the s4 harness or is it worth trying to put the BAC on?

 

Its got to be the BAC. You said you have the water temp plugged in. That leaves the BAC.
The connectors are oval on the S5. You could get a new connector and splice it into the wire harness. Don't know if that would work or not. Or just check out the classifieds. Can't be too much.

good luck

 

Gentlemen,

I have an 87 and an 88 turbo harness in my possession so I would like to clear a few things up.

1) the BAC valve uses a light blue fuel injector connector (Bosch EV1 style) with an offset tab. It might look green because it's so old, but its original color was blue.

2) the water thermosensor uses a green fuel injector connector (Bosch EV1 style) with an offset tab.

3) the 86 - 87 1/2 production harness, which has the resister box for low impedence injectors, uses a Bosch EV1 style connector for the injectors, with a centered tab. the injector connector is brown/tan for this harness

4) the 88 harness, which does not have a resistor box and uses high impedence injectors, uses a Bosch EV1 style connector for the injectors, with an offset tab just like the thermosensor and BAC valve. the connector is red

5) on the turbo harness at least (I haven't worked on a nonturbo in a long time) the water thermosensor connector is located near the fuel injectors and is not particularly close to the BAC valve connector. you can't mix them up too easily.

 

Thanks. I may try splicing it in. I would really like to hook the BAC up but the connector doesn't fit.


I noticed this also. When I took the old engine out I labeled everything clearly and the water thermo sensor is hooked back to where I took it out. The connector in question was never hooked to anything and the old motor hada blockoff for the BAC so it was never hooked up.

 

Wow, this sure got complicated. So your harness has two green EV1 connectors on it? Could happen if someone spliced it. If so then bostonspgs was right, my bad dude.

If your car idles fine without the BAC, then it's not really needed. Just crank the idle speed up to prevent stalling due to loading the alternator (lights, fan, etc).

 

Not a prob , but to the op get the bac do it right. 1k isnt an idle . The bac is helpful with quick stops , music and any other electric loads. As opposed to high idling it whether or not it needs it

 

sorry guys i stand corrected.

 

Alright thanks guys. Ill give splicing it in a shot. I would really like to have the BAC for idle reason such as electrical loads and all that.