Lazy tach in R/T

[mark]

is there a fix for having a Lazy tach in my r/t

there are times that it shows 0 at idle, and there are times it shows around 1k at idle. then there are times where i rev it a little and it goes to maybe 3k, then there are times when i rev it the same, and it shoots up to around 5k. when engine sound its no where near 5k, it just seems to act like a pendulum(sp?)

this is because there is no distributor and spark is by coil pack right?
will an aftermarket tach fix this, or would an aftermarket tap into the same signal as the stock one and I'm back to square 1?

much appreciated.

-Mark

[j4278h]

anyone got ideas my r/t is doing the same and i'm about ready to set it on fire

[TopDollar69]

There is a tach driver board on the back of the speedo assembly that is bad. I have the same problem with my 90 Spirit ES. I have been told that cold solder joints on the board can cause the problem, but i reflowed every oint on the board and it didnt help. You can get a new one from chrysler or go to the local yard till you find one that works.

[mark]

I went through and hit up all the joints with solder, as well as reseated the two boards that press onto the main board. my lazy tach is gone.

thanks!

-Mark

[Tony Hanna]

Bump for a good thread!
I'm having the same problem with mine. I'll check that out tomorrow.
Any tips on getting the instrument cluster out? This is the first time I've ever needed to get into the dash on a TM any farther than replacing the radio. I'd like to avoid breaking any plastic due to hidden fasteners, etc...
Thanks in Advance,
Tony

[mark]

the upper piece around the left vent, and around the traveler is all one piece, it just pops off, then there are screws that hold the instrument cluster in, and wiggle it out with the steering wheel down as low as you can get it (tilt steering)

[TopDollar69]

Its pretty easy, just carefully look for all the screws.

[Tony Hanna]

Thanks Mark!
No speedo cable obviously, so I'm assuming there's enough wire in the harness that you can get the cluster out far enough to unplug it?
I'm gonna give this a shot first thing tomorrow. Hopefully it'll do the trick.

[Tony Hanna]

Its pretty easy, just carefully look for all the screws.

Thanks, I'm usually pretty good with the obvious stuff. It's those hidden fasteners on alot of interior trim that I'll mistake for a clip and end up breaking something.

[TopDollar69]

It's been while, but I don't remember anything complicated or tricky. The wiring has plenty of length to see the connectors.

Good luck.

[Tony Hanna]

Awsome! Thanks.

[mark]

good luck, post if you need anything

[martin kolner]

the tach circuit board is 4375410 and fits various models from 1988-95

[Tony Hanna]

good luck, post if you need anything

Thanks!

the tach circuit board is 4375410 and fits various models from 1988-95

Nice! Hopefully resoldering the joints will get it sorted out but that's good information to have if it doesn't.

[JDAWG]

mine is starting to do it to, a new board is like $114. Take a look at your gears while you have it out also http://www.odometergears.com/subpages/chrydod.html

[Tony Hanna]

mine is starting to do it to, a new board is like $114. Take a look at your gears while you have it out also http://www.odometergears.com/subpages/chrydod.html

Are the odometer gears a common failure? I guess I've been pretty lucky with this stuff in the past. Until now the only instrument problems I've ever had have been external (sending units, VSS, and a broken speedo cable in the Sundance).
It's nice to know you can still get replacements.

[Tony Hanna]

I've got the instrument cluster out. Looking at it from the back there are 3 boards. One small one on the back, and 2 larger ones on the top. Is one of these three the board in question, or do I need to dig deeper?
Thanks

Edit: Nevermind, I got it. Reflowed the joints and "adjusted" the pins in the connector for a little tighter fit, and the tach works great! Thanks for all the help!

[mark]

glad it worked!

[Tony Hanna]

Thanks Mark. I just took it for a drive a few minutes ago, and the tach is working reliably now. It's still not quite right though. It seems like the needle will hang for a second and then jump all at once. It happens in roughly the same spot on both accel and decel. It kind of leads me to believe that it's mechanical in nature (something is dragging or dirty in the movement). I think I'm gonna pull it back out tomorrow, disassemble the cluster and give it a shot of tuner spray. Hopefully it's just some dust in there.

[mark]

mine does something similar too, ive learned to live with it