Bizarre speedo behaviour

[fenderbender]

Just been out in a particularly spectacular example of this season's drought

I notice that every time the wipers move over the screen my speedo needle drops to 0 mph, returning to normal when the blades return to park. This is particularly noticeable on intermittent wipe where the needle leaps up and down in a diverting fashion.

When the wipers are on normal or fast wipe the needle gives up and stays at 0 mph.

I find this more amusing than annoying but does anyone have any ideas on what the cause and fix might be?

[Quietlybonkers]

Just a thought.......100 amp fuse gone? if it has, you may be running the car on its battery rather than the alternator. When mine had gone, the speedo said 55 at 4500 rpm in fifth.....! Eventually the car will stop working at all if I am right.

[2 sMoKiN bArReLs]

Mine has always done this on intermittent, and I've had the car 7 years.

I just ignore it & put it down to TVRness.

(same as bashing the dash top to get the blower to work)

[fenderbender]

Quietlybonkers said:

Just a thought.......100 amp fuse gone? if it has, you may be running the car on its battery rather than the alternator. When mine had gone, the speedo said 55 at 4500 rpm in fifth.....! Eventually the car will stop working at all if I am right.

Interesting idea but no, the charge circuit is fine.

[fenderbender]

2 sMoKiN bArReLs said:

Mine has always done this on intermittent, and I've had the car 7 years.

I just ignore it & put it down to TVRness.

(same as bashing the dash top to get the blower to work)

Agreed. The answer is not to go out in the rain...

[SpecB]

I am glad I am not alone. Mine does it very occasionally but only on the downstroke of the wiper. There is something in the mechanism chafing behind the scuttle as it can be heard with the engine off.

It isn't really a problem and I put it down to a TVR "feature"!