Quote:
Originally Posted by ag4ever
WileETundra,
So when the output capacitor went out, what did the NAV do?
When you were doing the initial investigation, I think you measured various voltages between 0 and 12v. Is that correct? If so, then there really should not be any problem with 12v going to the nav.
Another mod that I was thinking about was the potentiometer. Since this circuit only uses one "fixed" resistance across it, could it not also be replaced with a resistor? All we are looking for is a fixed voltage drop every 2 seconds, so an appropriate resistor should do the job. Correct?
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When the output capacitor went bad the NAV unit behaved as if nothing was connected at all. In this case the functions are enabled for 30-40 seconds when you first throw the switch to disconnect the factory speed pulse signal, then after the short delay is over the NAV realizes that no signal is present so it reverts to using GPS and locks the functions back up again. After removing the bad cap and twisting the leads together (to form a jumper) then the pulse was back and the device has been working fine ever since.
I did test numerous output voltages from the generator to the NAV however I did not test a negative pulse for any length of time other than the first few weeks of my original install. With the original device I only switched it on when I needed to enable the functions so the negative pulse was never on for an extended period. With the new single-capacitor device I have left it enabled all the time for at least several hundred miles over a full week now and it still works like a champ.
So I assume I had a bad capacitor to start with or the extended usage of the negative pulse and/or the continous return voltage from the NAV took a toll. In any case I think the single capacitor model is better since it is one less part to buy and a few less soldering points...
