Need help w/ a resistor

[gt40]

yep, looks the same to me.
what spadnos said :
the blue wire is use to monitor the MAF signal and when the voltage gets to a trigger point, the purple wire can draw some current away from the MAF (through the other resistor) to clamp the voltage to an acceptable level.

[Kooldino]

Ahh, i see.

And what about the resistor closest to the MAF? Isn't that dumbing down the signal a bit? Or is that automatically balanced out by the second resistor?

[spadnos]

Yeah - what he said I said

The resistor connected to the blue wire does nothing by itself. Since the MAF output is a current (not a voltage), the ECU will still get the same signal (I'm assuming that the blue wire goes to an input that effectively draws no current).

You only get extra / less current when you do something with the purple wire. The electrical principle here is that the current is the same at any point in a series circuit. If the resistance of the blue wire is very high (like 50k-100k), and the same is true of the purple wire, then you can ignore any effects they have on the current from the MAF to the ECU.

Clear as pond slime now?

- Steve

[Kooldino]

Not clear, but I guess I ain't gonna get it. :/

I guess I'm thinking about the resistor closest to the MAF as acting as if there is:

MAF -> inline resistor -> ECU

is that assumption wrong? If so, why?

[spadnos]

You're right. The resistor is in series between the MAF and the ECU.

The thing is, if the MAF is a constant current* device, then the series resistance doesn't matter - it will just increase its output voltage to make the current constant. So the voltage at the MAF is higher than it would have been without the resistor in line, but the current from the MAF, through the resistor, and into the ECU is the same as it would have been without the resistor there.

* constant current for a given sensor reading, not that it never changes

- Steve

[Kooldino]

I sure hope you're right.