Testing Rallye Dash

[Chaos-N-Mayhem]

I watched Cody's gauge testing video again and wondered if there was a diy way of testing the other Rallye components, speedo, tac, and switches before install.

https://youtu.be/-pKbNSStjas

[7E-Bodies]

GYC has a good episode on this, but I'm sorry to say I don't have the episode number.

[6pack]

Working in the calibration lab most of my life for commercial and in the Navy the biggest issue is most folks do not have a resistive decade box and the inherent design of the Mopar instruments.  First, a resistive decade box allows the user to place the exact resistance and voltage combination the check the reaction of the various meters for accuracy and precision.  The small instrument voltage box in the instrument cluster that Mopar uses is a strange device putting an average voltage to the instruments.  Why they did not just use 12 meters is a mystery to me.  You can bench check the meters using say 8 volts but it is hard to replicate the little voltage box with it's constantly moving relay method of operation.  The Mopar gauges are very sensitive to voltage fluctuations.  I found it best to replace their voltage device with a solid state 5DC voltage supply and calibrate the gauges on the bench for the best results.  I tested the gauges and several set-ups to come to this conclusion.  The wat GYC Mark Worman's way is a more functional test.  The first time I seen that episode I said constantly said to myself why is he doing it that way?  Why build such an elaborate test structure and not do it correctly?  His is at a high school level set-up.  But is better than nothing.

[7E-Bodies]

@6pack is this what you mean? Sounds like we have some similar background. I'd love to hear some of your methods. Always open to grasping new ideas. And I've put together the beginnings of a decent station. Ideas would be great. (Heavy electrical and electronic background)

[6pack]

That particular one is not always reliable and can be problematic; if you measure the resistance before you use it may work out.  The precision decade type with the dials are better and what I use.  You got a good start on a workstation there.

[7E-Bodies]

Yeah I have a better one made by Blackbox. It's buried in my van right now. You've got me wanting to find it. I don't use them much on new stuff. (I'm a substation protective relay tech).

[Chaos-N-Mayhem]

I'd be interested in seeing that and how to test a tach with it as well as any info on bench testing switches before the go in the challenger

[Arctoad]

A 7805 Voltage Reg is the best solution.

[shawge]

Can you hook up the tach to a running engine?
Barring that, do you have access to a function generator?  Apply 12v and ground where you normally would and connect the input wire to a function generator (square wave, amplitude around 12v) 

Frequency will be (RPM * 4)/60 for a v8
RPM    Hz
750    50
1000  66.7
1500  100
3000  200
6000  400

If you are handy w/ coding, the function generator could be made with a micro controller (ex Teensy) and a few misc components.

Edit: or with a 555, no coding required
http://www.learningaboutelectronics.com/Articles/Adjustable-square-wave-generator-circuit-with-a-555-timer.php

[Chaos-N-Mayhem]

Not sure if I am that skilled, but still really good info. I've always wanted to get one of those adjustable power stations, but there is other test equipment that is interesting to me also, but I probably don't have the knowledge needed to use them.