Re: Re: FSM Help - locating tach wire

From: Mike Schwall (mschwall@flash.net)
Date: Sun Feb 20 2000 - 18:39:41 EST


Thanks for the info. I went ahead and decided to run the engine without
the cluster hooked up this morning. I checked every wire and only one
gave me what looked like a tach signal. Weird thing is, it only registered
on the frequency scale on my meter, not AC voltage. It would read 0V AC
when idling. At idle it read about 150 Hz, and increased as the engine
speed increased. I'm hooking up a Viper 550 ESP car alarm, just to fill
everyone in. I tried the wire I found that carried a tach signal, but the
tolerance of the alarm is 1-6V AC . I believe the tach drive signal is
below 1V, or is a square wave that the meter can't read in AC mode, or the
alarm can't read, because it would fail to learn the tach signal when idling.

Next option is splicing into the coil primary feed or an injector wire. I
think an injector would be the easiest.

Everything works that the alarm controls. I don't have the motion sensor
hooked up yet, need some double sided tape. Hood and doors trigger the
alarm. I can't test the remote starter until I get the tach wire hooked
up. Think I make have to change the way I have my homemade neutral safety
switch hooked up, might have to splice into the clutch switch (alarm is not
intended for a manual tranny, so some riggin' is in order). Have to see if
it will bypass the clutch switch when the remote starter is engaged.

Back to work. Thanks for the help guys. Let me know if you find anything
on that tach wire. Sure would be a lot easier to splice into a wire inside
the cab.

Mike

> >From '97 on, the Dakota gauges were completely changed from the
>mechanical types to the led types, including the way they were
>wired.
>
>On the '97, the hookup went from sensors to pcm to Central
>Timer Module (CTM) via the data link bus to dash gauges via
>the data link bus. The CTM is located in the end dash by
>the glove box.
>
>You would need someone to trace it in the '99 FSM as it is
>more likely than not that Dodge has made wiring changes. Dodge
>typically makes a couple of functional changes in the PCM pinout
>each year.
>
>You can run an aftermarket tach by hooking it to the neg. (I
>believe) connector at the coil.
>
>Bob. Southern Ontario, Canada.
>'97 Dakota CC Sport, FR, 5.2L, 3.55 SG, auto.

__________________________
mschwall@flash.net



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