1991 Dodge Caravan - Tachometer

The vehicle mentioned in the title has 300,000 KM. Recently noticed
the tachometer rises smoothly with pressure on the accelerator, but
seems to over-register the engine rpm. The vehicle behave normally in
all other respects and the transmission fluid is bright pink. Could
the pickup or ECM, or TCM be at fault and where and what is the sensor
that generates the tach dashboard display.

Thanks

On Sun, 06 Mar 2011 16:07:13 -0800, redryderridesagain wrote:

> The vehicle mentioned in the title has 300,000 KM. Recently noticed the
> tachometer rises smoothly with pressure on the accelerator, but seems to
> over-register the engine rpm. The vehicle behave normally in all other
> respects and the transmission fluid is bright pink. Could the pickup or
> ECM, or TCM be at fault and where and what is the sensor that generates
> the tach dashboard display.

I believe that most tachometers from that era run off of the signal on
the points or whatever the timing pickup is on your car. So unless the
points are bouncing _really really bad_, or the timing pickup is somehow
misbehaving, then it's hard to see what may be wrong with the signal.

What leads you to believe that the engine isn't over-speeding?

There's a chance that something has gone haywire in the tachometer
itself. Is there anything that makes you think it's outside of the tach,
or are you just trying to figure out the system to isolate the problem?

--
http://www.wescottdesign.com

redryderridesagain wrote:
> The vehicle mentioned in the title has 300,000 KM. Recently noticed
> the tachometer rises smoothly with pressure on the accelerator, but
> seems to over-register the engine rpm. The vehicle behave normally in
> all other respects and the transmission fluid is bright pink. Could
> the pickup or ECM, or TCM be at fault and where and what is the sensor
> that generates the tach dashboard display.
>
> Thanks

Put a scan tool on it and see what it says for RPMs. Could be that the
stepper motor in the tach is failing.

--
Steve W.