Odometer not working 308 gt4

Need a little help please.
Odo is not working although the speedo does!
Can anyone advise on remedy/supply new one.
regards
char11ee

 

Not exactly local to you but you did ask.... http://www.paspeedo.com/

 

Did it work before? Did you do anything to it? At the very least, try to turn the knurled know to reset the trip meter and see if it works again.

 

Have owned my 308 gt4 09194 for 27 years, now on 20,700 miles, odo just stopped working while taking it out last sunday for its first run since june, the reset works.
Wondered if I can get involved in investigation or leave it to the specialists!
regards
char11ee

 

Hi
The circuit is quite simple, it is possible that the IC is shot or that the final drive transistor for the odometer is bad.
RJay posted the circuit sometime ago. Do a search for Rjay and speedometer, both he and I have posted about the lovely gadget.
The really good news is that replacement chips were available again (NOS) for a very reasonable price.

Calibration after repair can be done using the sound card of a PC along with free SW to make a frequency generator. If you want to go that route send me a PM and I will help.

New ones are available (for some models) from Ferrari of UK. Pricey and might not be the exact one for your car though.

Gerrit
http://dino308gt4.com

 

thanks for the info, there's a wealth of knowledge out there including your postings.
I read with humble interest, I admit this job is not for me, only the removal from car.
kind regards
char11ee

 

Guys,

I read with interest about the calibration software for the speedo using a sound card and ask if you could enlighten me further on that. I have a Mondial with both tacho and speedo out of calibration and wonder if this would work with mine. I have had the tacho apart as it was reading very low and found the adjustment pot and now it is in the ball par but not accurate. The speedo reads high by about 8mph at around 60 to 70.

Trevor.

 

Hi
here are some links to frequency generator sw for PC sound cards, some are free, some are inexpensive, all provide at least a trial period:
http://www.nch.com.au/tonegen/index.html
http://www.techmind.org/audio/
http://www.virtins.com/page3.html

Using the spreadsheet attached you can see exactly what frequency input corresponds to indicated speed. The coloured cells provide a place to input variables such as tire diameter. The 308 always generates 4 pulses per rev of the sender and the chip always divides by 32. (I made these parameters configurable for other uses). Somewhere along the line, the 3x8 speedometers and pulse generator design changed, probably with the 328 or QV. Those later ones do not have a calibration potentiometer. Similar approach should work for a tachometer although never having had one of those apart I can't tell you if there is a calibration potentiometer. At least your Mondial tach has an adjustment.

Gerrit
http://dino308gt4.com
View attachment SpeedoCalculator.xls