ECU rheostat ???

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Hi all
Kicking round under my dash (88 Rolla gti) is a switchable rheostat, has 10 positions kinda like an old school heater.
Anyway it was hanging down and annoying the hell outa me, switching it didnt seem to change a thing so I thought I'd find out what it did by just cutting the wires. yeah, smart.
After this the car stalled lots, idle was super low. So I connected it up again, now its all good.

But can anyone tell me what the hell it does?? I'll try and get a pic up of the offending crappy plastic box

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this is it...[/img]

[NooDleS]

Check your ecu. It's not some dodgy variable resistor adjusting the fuel mixture is it? See where the wires run to.

Turn it down to 1 and blast down a long road as fast as you can, turn it up to 10 and do the same. Feel faster or rougher? Start the car with it set to 1, start with it set to 10, see where it idles.

Otherwise...

Turn your lights on at night, adjust it and see whether the dash illumination changes or whether the height of the beam moves.

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I had a play yesterday, doesnt alter the headlights or dash lights at all, and didnt seem to affect performance on either setting, even with a thrashing.
I haven't had a good look to see where the wires go yet tho..

Any other ideas guys?