I have started to take a look at this problem today.

Tried another speedo. Not working. Problem here is I dont know if its a good unit or not??

Looked at speed sensor on car and according to Jeffs pictures its all OK.

However I just want to check if thats the case.

according to the thread Jeff says it produces a pulsing signal of around 1 to 5 volts AC.

Can I measure that with a Fluke multmeter with the rear wheels being driven up on axle stands

If so is it the V with the little wave above on the Fluke unit that I need to set it to?? Dont laugh!!!

I dont normally do diagnostics and meters!!!:clown:

 

Since the speedo never worked from day one of building the car Im starting to wonder if I created the problem during the build. Wiring loom was all TT auto with Hicas connections etc.

But I built the car as a non hicas NA manual. ?? Without the solenoids etc on the inner wing.

I have also deleted the power steering ECU???Power steering works fine without it. So maybe all the wires arent connected??

V~ is ac v- is dc bud

V~ is ac v- is dc bud

 

This is what jeff said..............................

The unit is a small pulse generator, as the cog is turned by the gearbox the stator is turned within the field windings which produces a small ac voltage of around 1 to 5 volts and as the unit is very unstressed there is very little that can go wrong with it.

So what do I need to set the Fluke meter to in order to measure the pulse generated???

You will most likely have 2 ac voltage choices upto 200 or upto 600 select 200 I Spose. I don't know if its poled so you will have to experiment. It may be faster and easier to pop in a known good one.

You will most likely have 2 ac voltage choices upto 200 or upto 600 select 200 I Spose. I don't know if its poled so you will have to experiment. It may be faster and easier to pop in a known good one.

 

I dont think it comes out without dropping the back of the box a bit. That isnt fast or easy on the deck at my age Plus my spare is just as unknown.Although it looks good as per Jeffs picture. Remember I built this car from a bare repaired shell and added bits from several breakers I bought over the years. There were always going to be some little issues doing it like that. This is one of them.:blink:

 

240Zs are much easier

hrm annoying. although I seem to remember there being a pressed dent in the tranny tunnel to be able to remove it. I was concerned myself over the reverse switch, but it slid straight out. Worth a look if its removable in situee it wont take two ticks. Good luck with the tests though mate.

I've been told the box needs dropping to change it. I've taken my car in today to have the speed sensor changed along with a few other things. I'll let you know how it goes.

Well a happy end to my speed sensor issue.

The culprit was the signal wire behind the speeedo head. In the past this wire had been cut by someone and subsequently re joined by a badly crimped bullet connector which didnt...connect.

 

Here is some info for reference......................

As Jeff TT already said the most common fault with the sensor in the end coming loose. His fix is simple.

To test for a faulty sensor you need to connect an oscilloscope across the two wires coming from the sensor. Turning the speed sensor then produces the variable pulse which shows up on the scope in wave form . Altering the speed of turning alters the frequency and height of the wave. You can do this test on the speed sensor plug itself under the car and easier .. in the engine bay and also directly behind the speedo on the circuit board.

All the time the car has the rear wheels off the ground so you can "drive" it in gear for the test.

A process of elimination soon showed where the fault was, backed up by a normal "continuity test".

The offending connector was replaced and now I have a working speedo.

My thanks to the helpful suggestions on here including Jeffs original thread.:flowers:

And massive thanks to my clever mate Steve who came with the scope today and did the stuff!!:bow:

Tomorrow I just have to put it all back together..........................................:blink:

And drive it!!!!:nana2::nana2:

 

Hopefully my experience will come in as useful for someone else