daily driver problem

[Jokester]

Maybe some of you folk in cold country have experienced this.  2005 Lesabre.  When outside temps get below 5 degrees, the speedometer gains speed.  This weekend it was about 1 degree and the needle went all the way around past 140mph and ended up pointing to R on the gear selector.  This happened once before when I was in Colorado, but is self corrected when I got out of the cold country and into Denver.

Any idea of a cause?  Anyone have a schematic?  I don't know if the VSS controls the speedometer directly, or if it feed the computer and the computer feeds the speedo.  Everything else seems OK.  Tach works normally, cruise control works normally.  Didn't experience any engine shutdown issues when it went over 120.

Thanks for any help you can offer.

.bjb

[58 Yeoman]

Sorry I can't help you with your problem, but it sounds like it may be a problem that Buick has had for many years.  Back when I was a teenager, my dad gave me a '57 Buick Century, and when I reached 60 mph, it zipped right up to top speed.  Funny, I didn't feel like I was going any faster.

[enjenjo]

I believe you have a VSSB, a buffer that is fed by the VSS. this takes the signal, sends it to the computer, cruise, and speedo. As I recall, it sends every pulse to the computer, every second pulse to the cruise control, and every 4th pulse to the speedo.  There is no mechanical connection.

It may just be a bad speedo head. A motor drives a magnet that moves a cup that the needleis fastened to. If it's dragging, it will make the speedo read too fast.

[Jokester]

I wonder why it seems to be temperature sensitive.  It has only happened when the temp was 5 or below, which usually isn't often in Kansas City.  This year has been an unusually cold one so far.  Maybe I'll wait til tomorrow when it goes up to 30.  It might self correct.  Ha.