Mr. Big Ram

tan yj... or anyone else for that matter. Could you post up a copy of those tach instructions? Should be recieving my tach in a day or two, want to make sure I get it mounted in the right spot!

tanyj

Did you get the factory metal plate that goes under the dash to reinforce the plastic? I'll be pulling the dash apart again in the very near future, so if you want, i can trace it so you can fab that up, too. & yes, I'll try to remember to scan it and post it up. Maybe it can be stickied.

apwatson50

Wow, didn't realize there was a metal reinforcement plate, that would be good to have!

Trebor

FWIW, here are a few pictures of the factory supplied tach wiring harness used in the 1989 Dodge that I have and there is not a PCM installed on the fender. Under the dash there is what looks like an intermediate adapter cable between the under hood tach cable and the cable that leads to the tach head. I believe it may be there to pick up voltage from the 1989 wiring harness to the tach head and probably not much more. Too wet outside to continue any further.

The tach wire comes through the grommet in the firewall (bottom right corner) and into the back side of the plug at the center right in the picture. EDIT: The opposite end of this plug which is facing you is the tach connection. I had assumed this was where the power switched leads were but instead they are attached to the same side where the sensor is connected. Those power switched leads are the red- orange- and black.


EDIT: The red orange & black power leads are fed from the connector plug shown in the center of this picture. The tach leads are just to the right coming out of what looks like a piece of plastic tubing and drop out of view in the lower right corner of the picture. RED-white-orange- gray:


There is no PCM in this truck:

Mr. Big Ram

Find out when I get it ! Buying a used unit from someone. Should not be too hard to fab one up if not included, just concerned about where the holes need to go... if thats an issue at all?

apwatson50

I got mine from another truck that had it installed on the steering column. But I then moved it to the dash and I just set it up there about where I wanted it and turned it so I could see it, then drilled a hole. I don't think its that important to have it perfect, just to where it looks decent and you can see it!

Mr. Big Ram

Thats what I wanted to hear! Going to try to get as close to my A pillar gauges as I can, will post pic when up and running. Have a tach in there now that is running off the alternator, but can not seem to get the DIP switches set correctly, reads right at lower RPM's, but is off at higher RPM's. It had a sensor in the bellhousing on my Getrag, but I did not want to drill a big gaping hole in the new bell when when I did my 4500 conversion last summer.

Trebor

I added a few pictures to post 34 showing the under dash wiring of a factory tach installed in a 1989 Dodge. I believe this was discussed before but there were no pictures available.

wannadiesel

That looks like a non-intercooled truck, it would be a '91 not a '91.5. '91.5's have an intercooler and a "baby" PCM that runs cruise and OD but not the charging system or A/C.

Crossy's son

Awesome! just what we need.

So the tach itself must be diff. also.

How many wires run into the harness that the tach plugs into? it should be, lighting,ground,power, and signal...

I only see 3 wires in that plug

Trebor

From memory the door tag says MFG 3-89 This is a parts truck that I am dismantling not the one listed in my signature. I actually have three of the nonintercooled pre 91.5 trucks and two of the intercooled post 91.5. Most are donor trucks for the three crew cab project trucks I want to do provided I live long enough!

Trebor

This is why we need somebody to post a copy of the wiring diagram that comes with the factory tach. In this case there are only 3 wires in the tach connector plug - red - orange - and black.

comptz

do you mean this? from looking at the pic it looks like you would be missing the grey wire which is the signal wire i believe.

https://www.dieseltruckresource.com/...d.php?t=185725

Richie O

This is from Isspro for there tach but may answer your questions.












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Trebor

The rain stopped today and I went out to take a better look at the tach wires and discovered I traced the power leads and not the tach leads. I did an EDIT on post 34 to correct where I veered off in the wrong direction. The tip was the missing gray lead to the tach head noticed by Crossy's Son (Good catch). So this combined with all the previously linked wiring info should allow anybody to install a factory tach into a non-PCM pre-91.5 truck.