Speedo is jerking all over the place *update*

[Wiscon_Mark]

I noticed it on a longish trip today. It happened mostly at high speeds (60-70mph) but the speedo was jerking around 2-3mph while I was moving at a constant speed. No other electrical devices nor the Tachometer or other gauges were fluctuating at all. Speed sensor going bad? Maybe the speed sensor is just loose? Ideas?

[Yokosilver]

Sounds like it is loose. I had a similar problem with an old pick up I had. All I had to do was tighten the cable on the back of the gauge and it stopped.

[Wiscon_Mark]

That's a good suggestion- the tab on that harness is broken and there's obviously more vibration at higher speeds. I'll check it out.

[legacyB4RSK]

Had that problem too on my 2001 Legacy, turns out the pin for the speed sensor had to be replaced.

[Wiscon_Mark]

I'm going to revive this as the problem hasn't gone away (I did reseat all of the connections on the back of the cluster). It only seems to happen on trips lasting longer than 10-15 minutes and usually only shows up at speeds of over 40mph.

Here's the interesting bit: using cruise sometimes fixes the issue. The speedometer needle will be jerking around all over the place (usually at 5-10MPH lower than the actual speed - I use the tach to calculate) and when I engaged cruise control it snapped right up to where it was supposed to be. Didn't cause a problem the rest of the trip. Today, it didn't fix itself until I "canceled" cruise and went away for about 5 minutes. It's really random and intermittent.

My question is: what would cause the cruise control to "fix" (albiet temporarily) this problem?

Note: Cruise control always holds at exactly the speed I set it at. It doesn't drop down to the speed the speedometer shows or jerk around when the speedo jerks around. So I don't think its speed sensor related unless cruise uses some other system.

[Wiscon_Mark]

Anyone? I can replace the electromagnet that controls the needle (I have a spare speedo sitting around for parts) without replacing the odometer portion of the speedo, but that would require removing the needle which isn't my favorite plan.