My km/h needle on the dash is fluctuating like crazy from 100 back to 80 then to 110 etc when crusing on 100/kmh .

I was wondering what controls this dial needle, and possible solutions to the problem? Thanks!

id guess the speedo sender unit on the rear side of the gearbox has a fault, maybe bad connection on the plug or worn gear

I'm assuming the cars in your sig block:

Put the inst cluster in diagnostic mode (see the tech docs), check if the digital speed is doing same.
Does cruise control hold it at the set speed??
Is the car auto or manual??

ef ghia v8 -auto

Now the auto is playing up- after a service 2 days ago and replacement of s5 solinoid....was shifting great for 2 days, apart from the little delay to get into D properly..

I noticed this morning the needle getting more crazy - I think the speedo stays at 0-60 now!, and cruise has not held properly for a week or so, pedal going up and down by itself!

Now auto is stuck in first! It went nuts from holding 2nd, then neutral to third now back in first and stays there - all on the freeway

I have been told the auto has adjustable bands- by the auto guy - so its an earlier tranny, I dont know why i did not go in LHM, Maybe i should take out the auto fuse to see if i can entice it to do so? SAVE MYSELF A TOW!

Can speed sensor contribute to playing around with auto? and cruise not holding set speed and dash needle flickering?

Can Inhibitor switch contribute to the above, or only symptom of this "inhibitor switch" is car not starting at all??

I will also note that before car decided to really play up, the revs used to sit on 1,800 at an indicated 100 km/h- where as this morning it was on 2,000 at 100!! like no overdrive drop.. Just like the ghia 6 with the 3.45 lsd....but u expect that to sit a little higher on 100.

I have no fuggin idea!!

Im hoping this speed sender is causing all of this - as he said auto was in very good nick, apart from stuffed S5???

I also forgot to add that the auto service guy i chose (seeing as though he advertises as C*%$@g Automatic Transmissions) I Thought you know, he may know his stuff......

He informs me when he serviced my car's auto and replaced S5, V8's use a combined ECU for engine and Auto- Im led to believe all Windsors eb-el at least have an independent ECU for auto- there goes my faith in him!!!!

Yeah, Info FAIL. V8's don't use combined ECU lol. Maybe the little gear the cog sits on is wonky, it's only held on by a clip onto the main shaft. (the cog inside the box) have you pulled the speedo sender off the box yet?

Now that there is more detail with the fault, I think you have enough replies with info to fix it.
Let us know how you get on.

instead of the tow, I went to see if I could take the car after work tonight-

still it would not go out of 1st gear, with no reading of km/h at all- for some reason it would not engage limp home?

I took out the auto fuse to engae LHM. This worked.

My question is can speed sensor effect car so much so that it wont change from 1st gear, and makes cruise jumpy -?

s**t yeah....as the auto is electronically controlled the auto computer relies on the speed sensor to determine when to shift gears...

Turns out the Speed Sensor was fine, the culprit was the little plastic gear set! The inner sprocket was worn down to nothing, the one on the sensor shaft had barely any teeth left to mate with the inner!

Sure enough, the snap on diagnoser picked it up also 'Speed sensor circuit"

Car now has smooth changes again, cruise control hold perfect and a needle that goes where it should.

I was lucky too, as Bayford's Tranny centre only had one 3.23 sensor gear left!?