View single post by Mark Rosenbaum
 Posted: 08-26-2005 03:59 pm
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Mark Rosenbaum



Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
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 Re the voltage stabilizer.  Sorry for the confusion, I didn't explain that at all well.  My thought was that the stabilizer used for the temp and fuel gauges was also providing power to the tach, or to the ignition current line that runs to the coil.  This could be due to a miswire by a PO, to some sneak current path involving a bad ground, or to some strange wiring fault where two unrelated circuits are somehow connected.

The blower switch is pretty independent of everything else.  It provides a ground for the blower motor either directly, or through the big printed-circuit resistor on the side of the heater box.

Your comment that things were working fine for a while suggests that a miswire is not the cause of the problem.  That being the case, I'd look first at the connectors for broken wires or pins, stray wire strands, etc., and if necessary check the wiring harness for signs of damage that might suggest damaged wires inside.

One other thought.  I failed earlier to reflect upon your comment that once things warm up, applying the brakes has only a small effect on the tach.  This could be related to the normal slight change in engine speed that occurs whenever it must pump air from (i.e. "apply vacuum to") the brake booster.  This can be proved or disproved by disconnecting and plugging the vacuum line to the booster, then applying the brakes.