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Re: [T3] Wiring Voltmeter


On 17 Sep 2006 at 23:43, Constantino Tobio wrote:

> Hmm. You got me thinking there. I get 13.5v at idle at the battery, but
> when I was reinstalling my AAR this weekend I was getting around 11V at
> the AAR wire. I also was getting 10.5-11V at the coil when I was going
> through my ignition saga.

I would try to measure the voltage right at either side of the ignition switch, 
just to see if there is something going bad in there. I've never actually done 
this, but I wouldn't expect to see more than 0.1 V of drop across the switch 
itself. More than that is likely to mean that the switch will be getting hot 
and burning up soon.

To do this measurement, don't do measurements to ground, just measure directly 
between wires going into and out of the switch. You can use sewing pins pushed 
thru the wire insulation to make contact with the wire inside.

> The car has been starting great, but it seems to be a little erratic
> once warmed. What if the FI brain is getting this voltage- it would run
> like a car with a bad VR, right?

The brain gets its power from the FI main power relay, not thru the ignition 
switch. This was done for exactly the reason you are worried about. With the 
power coming thru the relay, the voltage is no longer dependent on the ignition 
switch and doesn't even have to run the extra wire length up to the dash and 
back. High resistance in the FI main power relay is always a possibility, but 
I've never actually seen it happen. As long as that relay has good connections 
to the battery, ignition switch, and ground, it always seems to be fine.

-- 
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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