Getting speedometer to work?

[gergstuff]

Hello,

I have been struggling through some issues with my recently aquired TR-6 with a Chevy 4.3 V-6 swap.

So far this forum has been very helpful.

The car has a T-5 5 speed and I believe it to be a World Class ediction based on what I have read elsewhere.  It would seem that one of the prior owners made an attempt to switch the speedometer to an electric unit while using the original gauge faces.

There is an electrical plug on the tail of the transmission and wires presumably leading to the speedometer.  When the ignition is switched on the gauge needle jumps up about half way then down to zero.

The problem is, when driving it is no where near accurate.  it doesn't seem to register a speed any higher than about 30 and I know I am going faster than that as "the lines on the road just look like dots" (Hot Rod Lincoln-Commander Cody and his Lost Planet Airmen circa 1972).

The question is how do I go about getting the speedo to give me an accurate readout?

Thanks in advance for the help.

Craig

[DiDueColpi]

Sounds like the speedo is working. Just needs to be calibrated. The needle sweep is just the speedo initializing and is normal.
What brand is the speedo?
Generally there is a button somewhere that you press and then drive a measured mile to calibrate it.
Once you find out the make of the unit the rest is easy.
Cheers
Fred

[gergstuff]

Hi Fred,

Not sure of the make of the speedo guts I will have to pull it out and find out.

I will keep my eye out for a button to press.

Craig

[rficalora]

I have a problem with mine too -- don't want to hijack your thread so won't share it here, but one of the suggestions I found while researching is that sometimes you can get interference that affects the "sender" or pulse wire.  The suggestion I read was to twist the power & sender wires all the way from the VSS to the gauge -- that apparently can help ensure you don't get electrical  interference.  Also, I've read that you should ground the speedometer & VSS each on their own -- not tied together, not on a common ground & not tied to other gauges.  Not sure why that is, but apparently it can affect how accurate the speedo is.  I haven't tried either of these suggestions yet so can't comment on whether/when they help; just thought I'd share them to see if they prompt others with more experience to chime in.

[gergstuff]

I got the speedo out but I will be darned if I can find a name on it anywhere.  There is a little black button too, I pressed it under a number of different situations with no discernable effect.

I managed to knock the needle off of the post so...now what am I going to do?

Anyone know a few names of companies that offer these electric speedo units?

I will try to do some searching too.

Thanks,

Craig

[gergstuff]

Okay I found a website for Autometer speedos with directions to calibrate.  I will give them a try, it can't hurt.  First I have to glue my needle back on.

Craig

[74ls1tr6]

Some electronic Speedo's have a dip switch on the back of the Speedo. On mine ( I have Autometer ) it was set up for a V8. It would show that I was going very slow. My ls1 engine VSS calls for a pulse of a 4 cylinder. So I set the dip switch for a 4 banger engine. Now my speedo was closer. Also for my application needed to use my HP tuners software and make sure I had the right tire size and rear end gear ratio programed in. Once I did this my speedo is accurate.

Autometer gauge calibration setup. You need to have a 2 mile distance marked out somewhere or have someone in another car drive you to 2 miles. First hold down the black button (mine was on the front of the gauge) for about 7 seconds, I think the needle went all the way to max speed then went half way. I let go of the button. Drive your 2 mile distance stop then push the black button again. At this point your gauge should be setup to read the right speed. As you drive the 2 miles the odometer numbers start going wild. What it is doing is clicking off the pulses for your 2 mile drive.

I hope this helps you out.

This is probably a little more accurate from Autometer site on how to calibrate a speedo, I went off memory!

http://www.autometer.com/tech_faq_answer.aspx?sid=2&qid=40