Dead Speedo.....

[Paul1566]

Whizzing along tonight and all of a sudden speedo stops working....bugger
then OD light starts flashing...... double bugger

Kept going and just guestimated speed....... funny cus i got tugged last week for whizzing too much but as it was 1am and roads empty nice man let me go....
Not going to whizz as much till its fixed...

Found sensor check by mr bushwacker :

Look at the plug end of the sensor and you'll see tiny numbers, 3 2 1.
Apply 12v to pin 1.
Earth pin 2. plus the negative probe of multimeter.
Positive probe of multimeter to pin 3.
Set meter to 20v DC, switch on power supply and turn the plastic cog on the sensor. The voltage reading should fluctuate between 0 and 9 volts, if it doesn't then the sensor is stuffed.

Guess what i am doing tomorrow night in the dark.....

[Paul1566]

Spent ages reading so many confusing threads and have concluded that:

If the speedo itself was duff the OD light would not flash as the signal to the ECU would still be there, the speedo is just incapable of displaying the result.

If the OD light flashes and the speedo does not work, its the sensor not sending info to the ECU which in turn senses a fault and triggers the flashing OD light, obviously the speedo does bugger all as the sensor is fubar.

So question..... if i undo the bolt securing the sensor will half a gallon of gearbox oil deposit itself on the nice company underground garage floor,
or do i wait till i'm at home and bung a bucket under it..????

[BUSHWHACKER]

Only a dribble comes out when you pull the sensor from the hole. Just don't drive the truck with it out or you'll leave a trail of gear oil down the road.

[Doc B]

Hi Paul

I have a spare sensor in my garage if you want to do a replacement test. If that's definitely the issue then we could come to an arrangement.

I replaced mine but it turned out to be the speedo in the end....

email me at: david.bryant@fife.gov.uk if I can help

[Paul1566]

Cheers Doc B will keep that in mind if mine is duff and ping you an email

[Paul1566]

removed sensor and could not see numbers so switched ignition on and probed connector on truck to determine which pin was the 12v supply.
Went back to bench and connected sensor as bushwackers test and span the gear with rubber wheel in cordless drill.
got a constatnt 6.4 volts what ever speed the wheel span at.
Should the output vairy with speed ? or is it a pulse thing ?
It has got mph converter as the speedo has the k blacked out and seems to run nearly right as the policeman told me last week when i was slightly speeding home at 1am, he let me off with a warning. He told me roughly what i was doing and thats what my speedo said just before the blue lights came on in the rear view mirror.....
If the converter was fubar surely the ecu would not sense a fault as the fault would be on the input to the speedo not the input to the ecu ????
Don't want to take dash out to bypass converter if i don't have to. wouldn't know what it looks like anyway......

[BUSHWHACKER]

Only turn the cog by hand!!!!!

It's a MRE type speed sensor........
http://www.autoshop101.com/forms/h36.pdf

[Paul1566]

Sorry for double posting mr bushy sir will only post on the darkside....