Anyone ever have to trouble-shoot Smith's electronic speedo?

Anyone ever have to trouble-shoot Smith\'s electronic speedo?

Hi guy's...

Just wonedering if anyone has ever had any luck in fixing this goofy problem. I have Smith's instruments and when the parts arrived, a VDO electronic pick-up was shipped. That did not work and I have since received a correct Smith's pick-up. I installed it with no issues, and the speedo seems to behave more like a tach than a speedometer! When sitting still, when I rev the motor to 2,000 to 3,000 the speedo goes to 30-50 MPH! Go figure. Any thoughts? Could the speedo head have been damaged by the VDO pick-up? Anything obvious I am missing? Any other CAV owners out there have the same issue?

Here's the Smith's parent site with some good info!
http://www.caigauge.com/Gauge_Fitting_Instructions.htm

I do appreciate it...

Sorting through all the issues...

Tom "Can't tell how fast I'm really going" Hughes
 

Pat

Supporter
Re: Anyone ever have to trouble-shoot Smith\'s electronic speedo?

Tom,
It may not be relevant but I had a similar issue with the tach because of the CAV wiring so much amperage through the ignition switch. It was greatly reduced when I installed the relay kit mod.

Hope that helps,
Veek
 
Re: Anyone ever have to trouble-shoot Smith\'s electronic speedo?

My CAV tach (VDO) had the same problem. Intermittent, and I never got time to track it down. No speedo problems, though.
 
Re: Anyone ever have to trouble-shoot Smith\'s electronic spe

This could be a problem from ignition interference...most of the electronically managed vehicles made use an electronic speedo, and it is really a magnetic sensor that pulses the speedo head at a designated amount of pulses per mile, (or kilometer), most of these units have a filter to knock out spurious signals such as ignition or other sensors in the vehicle. I would check for the availability of that filter, and also the cable should be shielded and grounded at both ends.
Good Luck
Phil
 
Re: Anyone ever have to trouble-shoot Smith\'s electronic spe

Thanks Phil,

I appreciate the advice. I did a lot of searching today & jacking with the unit. So far, it still acts like a tach!

http://www.classicinstruments.net/index.phtml?catid=54

These folks have some trouble-shooting instructions...

I'll try to test it by getting up to 60-70 MPH then switch off the ignition. If interference is the case, then this should bear it out. I will try to put a supression capacitor in the system - just can't remember how at the moment. It's been 25 years since I last did it! If anyone remembers how, lemme know! I will try the stereo shop in the AM. I also tried a new cap & rotor, and a new coil wire. I can shield some of the cable, but it won't be real easy. I have also sent a note off to the manugactuer.

http://www.caigauge.com/

I appreciate the help... Keep it coming!
 

Lynn Larsen

Lynn Larsen
Re: Anyone ever have to trouble-shoot Smith\'s electronic spe

Have you rerouted the wiring to your speedo so that it isn't with or near any other wiring? I took mine in a completely different path than any other wiring. I also used Cat 5 ethernet cable as it is twisted which helps self shield from bleed over. I used a 6 pair cable and grounded ONE (and only one) end of two pairs to also provide extra shielding. If you ground both ends, you can get a ground loop current that could make the problem worse. There is no doubt that you are getting some induced current in the speed signal wiring from somewhere if it is acting like a tach and following engine rpm. Speaking of which does your tack have a filter on it?

Lynn
 
Re: Anyone ever have to trouble-shoot Smith\'s electronic spe

Ok, almost have this one solved.. If you disconnect the wire from the coil to the tach, the speedo works just fine. Apparently, there is some bleed-over from the wire coming to the tach from the coil, and the speedo sensor wire. Just do not know where,,,, Hope to have it finished soon.
Thanks folks,

Tom 'Almost about to have this thing fully sorted & safe' Hughes
 
Digging this old post up....
I had a Speedhut speedo fitted and working in my GT40 and have just swapped to the Smiths GT40 speedo. Im having trouble setting up the speedo to read the Audi 01E Speed sensor. The speed sensor is an inductive low voltage unit. I have the Smiths White/black wire and Red/Blue connected to the sensor. Any help aprreciated
 
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