Re: Speedo error

[Orin Eman <orin@WOLFENET.com>]

> From: "Smeins, Larry" <lsmeins@ball.com>

> >My 87 5kcst has had a very optimistic speedometer from day one.  The
> >odometer seems to be right on.  I thought I had a mechanical speedo and

So does my 86 5kCSQ.

> I also noticed that the speedometer wasn't very accurate.  30, 60 and 90mph 
> should correspond to 55.4, 110.7 and 166.1Hz.  My speedo was close at 30mph, 
> about 5mph out at 60mph and more than 10mph out at 120mph (not that I plan 
> on doing much of this speed).

Very similar to mine.  Are we seeing a trend here?

The speed displayed immediately after resetting the average speed
on the trip computer is however accurate.

> The chip that drives the speedometer and the odometer is an ITT UAF2115.  I 
> couldn't find any reference to this chip anywhere, so I e-mailed ITT.  They 
> sent me a PDF file with the data sheet for a UAF1025 which apparently is 
> identical.  This shows that there is a series resistor connected to the 
> speedo which is used to adjust the speedo sensitivity.  The resistor on the 
> circuit board was 51ohms.  I found that 54ohms gave a much better response 
> along with a realignment of the mechanical zero position.  The speedo is now 
> within 1mph between 30 mph and 60 mph and within 2mph over the rest of the 
> useful range.

Wonderful!  Just what I need.

Thanks for this one,
Orin.