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XA2 power off D-in impedance

6 years ago in Expansion modules / XA2, XS2 • updated by 6 years ago • 2

I have D-in G, pin #38 hooked up to the brake lights of a truck to detect when the brakes are on.

I recieved a report on one truck that the brake lights don't work when the IQAN system is powered off.

Does the impedance change radically when the system is powered down?

the book states 62 kohm pull-down in parallel with 470 pF. I can't imagine that would draw enough power to keep the brake lights from illuminating.

Is this a faulty module? or is this normal and I need to add a large in-line resistor on all trucks in the field wired this way? Are XS2 modules the same way if this is normal?

eta: when I use a multi-meter on another XA2, I get 62K ohms between pin #15 and pin #38, so I am leaning twoards this being a bad module.

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6 years ago

DIN-G on pin 38 is one of the VIN combined pins, this will always just have the 62 kOhm pull-down to ground resistor.

It is extremely unlikely that the resistor will be shorted, but on your module the capacitor might have failed short.

If that is the problem, it is a fault that should be possible to repair for less than the cost of a new module.