V8S (LT77) Speedo Sensor

[v8s4me]

I've repaired my spare speedo sensor (thanks Tim) but don't know how to test it. I don't want the hassle of fitting the unit without knowing if it's working first so I'm wondering if there is any way of bench testing it. I've got a silly-scope but don't know how to use it Any suggestions?

[phillpot]

Without seeing it I may be talking nonsense (it happens) but could you not wire it up and spin it up somehow with a drill?


Seeing the speedo whilst underneath might be the tricky bit

[v8s4me]

It getting to the unit and the wiring that's the problem. The wiring is tucked down the side of the 'box with the exhaust in the way. I could lift the centre console and see if the connector can be pulled up but I don't want to risk pulling it off completely until I've got a replacement. Because of the access I only want to do this once.

[The Big G]

If I remember correctly it's only two wires that connect the sender to the speedo. These could be extended with a couple of spade connectors so the speedo is directly linked to the sender. Then spin with a drill and see if there is a increase on the speedo. A silly question, but have you checked the continuity of the wiring as it chafes as it runs past the chassis and bodywork and can be the source of problems.

The sender itself pulses a set amount of times per rotation (if I remember correctly from my speedo issues five years ago) there are 4 and 8 pulse units for the LT77. Can't remember which is correct for sure but think it's the 8 pulse unit. A oscilloscope should be able to be set up to show these, it would be a good chance for a play

Sorry my post is a bit vague but hopefully it's of some help.

[tinks v8S]

Think it is 8 pulse. I fitted a new one and my speed was half what I was doing and was told I had fitted a 4 pulse one