The tach on my 91 RS 305 TBI is messed up. Just messing around with the throttle at about 1/4 to 1/2 throttle shows I'm redline. I was doing about 80 MPH on the highway in OD and the tach showed around 3200 RPM. Is that normal? The kid I bought it from said the VSS was replaced. Any suggestions?. Thanks

 

Search for "tach fix" with relevance selected...

Very common on our cars. Nothing to do with VSS. Its a bad resistor pack. That search will explain.

 

The kid you bought it from has probably no idea what he's talking about. VSS is for the speedometer, not the tach.

Nimrod is right, the calibration resistor pack is notorious for failing over time and making the tach read incorrectly. I've seen tachs that redline at idle.

If you're handy with a soldering iron and know a little about electronics, you can replace the bad resistor. And if you have a function generator handy (or can borrow one from a friend), you can even calibrate it to read correctly. Otherwise, feel free to send the tach to me, I can take care of that.

Lou

 

yeah, theres a thread somewhere on the tech articles that says about 90% of the camaros have messed up tachometers something to do with a resistor or a capacitor on back of the gauge cluster itself is burnt out, apparently gm didnt expect these cars to outlast the tachometer.still no matter what its all they want to outdo the imports then they come up with this.
----------
btw bigbabylou is there not a way that you can temporarly hook up a known good gauge like an autometer and calibrate it to that one then finish the install and remove the temp tach, just wondering(curious)

 

I would think so. I myself currently have an AutoMeter Monster Tach. Im sure both could be hooked up at the same time. You can install a variable resistor to fine tune it. I couldnt see how it coud be adjusted any other way.

To the OP, my post above will take you where you need to go. Or goto the articles section...

 

Yup, if you buy an extra tachometer and you trust it enough, you could use it to adjust the stock tach. It's not an easy job, howerver. You gotta adjust your tach while it's in the dash and while you're trying to hold 1000, 2000, 3000, 4000, 5000 rpm.
That's why I use a digital function generator and do it on my soldering bench. No noise, no smoke, no pressure, plenty of room.

Lou