Erratic Speedo Reading

[martinlaw]

My Speedo keeps going all over the place even when not moving.

Possibly some sort of interference?

Anyone had similar problem or can throw some light on the possible causes?

Thanks,
Martin.

[crafty]

Erotic Speedo Reading??

Possible cause #1 - Canam boys admiring each other's swimwear.

Edited by crafty on Tuesday 20th January 15:48

[suntiger1965]

martinlaw said:

My Speedo keeps going all over the place even when not moving.

Possibly some sort of interference?

Anyone had similar problem or can throw some light on the possible causes?

Thanks,
Martin.

Martin
As you might know i havent got an ultima yet however as im not sure how yours speedo is wired up i can only help in the ovious suggestions...
Usually eratic readings in speedos are an earth problem... Just follow the earth off the speedo and check the bolt is tight(and ground is tight on speedo if it bolts onto the back)...

if not, where is the speedo sensor(gearbox? or hub?? have you tried unplugging sensor to see if it still moves at standstill?? If so one wire of the sensor wires might be grounding out in the loom or where it goes through the bulkhead or even at the speedo its self....

Springs in speedos do become weak with age but alot older than yours and not usually at standstill

Good luck, as i hate wiring... think yourself lucky its not multiplexed

Dom.

[shithotfast]

I would also suggest earthing. On my car (which may have an older type of wiring) - the wire to the speedo from the sender was a shielded wire - ie had an outer wire covering the signal wires if you see what I mean. I "earthed" this wire at both ends, onto the gbox at the sender, and to the chassis at the dial/speedo end. This fixed it for me.

[Steve_D]

sthotfast said:

I would also suggest earthing. On my car (which may have an older type of wiring) - the wire to the speedo from the sender was a shielded wire - ie had an outer wire covering the signal wires if you see what I mean. I "earthed" this wire at both ends, onto the gbox at the sender, and to the chassis at the dial/speedo end. This fixed it for me.

It may have fixed it but for other reasons.
It is my understanding that screening should only be terminated at one end.
I do agree that the problem is likely to be an earthing issue and possibly the earthing of the screen.

Steve

[martinlaw]

Thanks for the advise guys.

i will check the earthing and let you know if solves the problem.

Cheers,
Martin.