Speedo not working
Discussion
Ok, speedo has not worked properly for the last year. It would read anything from about 50%-75% of true speed, then after about 10-15miles would start reading correctly.
It now shows no movement at all, although it did manage to get to about 5mph when I was doing 50mph last month.
Only good thing is it keeps the mileage down
(I keep a record each time I fill up with fuel so should be able to work out approx how much the mileage is out).
The rev counter works fine and annoyingly I have a spare brand new rev counter but not a speedo.
So where could the problem be and how do I go about testing? It's on a 2.9 V6
Thanks in advance
Russ
It now shows no movement at all, although it did manage to get to about 5mph when I was doing 50mph last month.
Only good thing is it keeps the mileage down
(I keep a record each time I fill up with fuel so should be able to work out approx how much the mileage is out).The rev counter works fine and annoyingly I have a spare brand new rev counter but not a speedo.
So where could the problem be and how do I go about testing? It's on a 2.9 V6
Thanks in advance
Russ
Russ. I've had a number of problems with my speedo so may be able to offer some advice.
1. The speedo is electric, as you probably know. The speed pickup can be removed from the gearbox through the gearlever gaiter hole. On my S2 you can remove the 2 screws at the back of the centre console and jack it up enough to get through.
It's held in with a single M6 bolt, 10mm AF spanner. And it has a short length of wire out to a connector block.
Lifting the unit it will come out of the gearbox for you to test it out. The plastic drive gear may also come out with it so you can check for stripped gears, etc.
With a 12v feed in you should get a square wave output when you rotate the pickup spindle. The red wire out is the signal line so whatever the other wire colour (I think it's black, for live??) is should be the 12v feed in. You also need to supply an earth to the earth braid round the red wire.
I got an auto electrician mate to check mine out as you need either an AVO meter or an oscilloscope and a power supply.
This should quickly show if the pick up and gear drive are okay.
2. If you trace the wiring from the back of the speedo then it will get you to a red 3 pin connector behind the removable cover on the right hand side of the console. It's the only red connector there if that helps.
The Red signal wire to the speedo is very very thin with the usual insulation an earth braid covering and another covering insulation. On mine the flexing of the wire into the connector caused it to break giving an intermittent contact.
So check for breaks in the wiring on both sides of the connector.
There are 7 wires going into the 3 pins on the car side of the connector. This link is clearly shown on the readily available wiring diagram.
I fixed mine by replacing the 3 way connector with a single wire coming out of each pin. These were then soldered onto the 2 or 3 wires from the car and covered in heatshrink to protect the weak signal wire from any stress.
3. The speedo could be broken. If you remove it then put in 12 volts to what I think is the Black wire, give it an earth to both the signal earth braid and the small earth lug on the back of the speedo and put a square wave into the red wire (Oscilloscope required again) then you can see if that's working.
HTH, PM me if you want any more help.
Bob
1. The speedo is electric, as you probably know. The speed pickup can be removed from the gearbox through the gearlever gaiter hole. On my S2 you can remove the 2 screws at the back of the centre console and jack it up enough to get through.
It's held in with a single M6 bolt, 10mm AF spanner. And it has a short length of wire out to a connector block.
Lifting the unit it will come out of the gearbox for you to test it out. The plastic drive gear may also come out with it so you can check for stripped gears, etc.
With a 12v feed in you should get a square wave output when you rotate the pickup spindle. The red wire out is the signal line so whatever the other wire colour (I think it's black, for live??) is should be the 12v feed in. You also need to supply an earth to the earth braid round the red wire.
I got an auto electrician mate to check mine out as you need either an AVO meter or an oscilloscope and a power supply.
This should quickly show if the pick up and gear drive are okay.
2. If you trace the wiring from the back of the speedo then it will get you to a red 3 pin connector behind the removable cover on the right hand side of the console. It's the only red connector there if that helps.
The Red signal wire to the speedo is very very thin with the usual insulation an earth braid covering and another covering insulation. On mine the flexing of the wire into the connector caused it to break giving an intermittent contact.
So check for breaks in the wiring on both sides of the connector.
There are 7 wires going into the 3 pins on the car side of the connector. This link is clearly shown on the readily available wiring diagram.
I fixed mine by replacing the 3 way connector with a single wire coming out of each pin. These were then soldered onto the 2 or 3 wires from the car and covered in heatshrink to protect the weak signal wire from any stress.
3. The speedo could be broken. If you remove it then put in 12 volts to what I think is the Black wire, give it an earth to both the signal earth braid and the small earth lug on the back of the speedo and put a square wave into the red wire (Oscilloscope required again) then you can see if that's working.
HTH, PM me if you want any more help.
Bob
Russ
Got a speedo off the S£ breaker, havent checked it as yet will do so first nice day. If its OK it might solve your problem, let me know if you are intersted.
BTW the rev counter has an identical three connector plug and its not far away from the speedo lead so double check before disonnecting
Got a speedo off the S£ breaker, havent checked it as yet will do so first nice day. If its OK it might solve your problem, let me know if you are intersted.
BTW the rev counter has an identical three connector plug and its not far away from the speedo lead so double check before disonnecting
Thanks for that info Bob.
I'll have a go at getting to the speedo pickup tomorrow, assuming the weather is nice (I wish I had a garage). Having to use an oscilloscope is getting way out of my league, not used one of them since college about 20yrs ago, and I didn't know what I was doing with them then!
Norman, I'll get back to you if needed. I want to get this sorted ASAP, before serious driving time starts again.
I'll have a go at getting to the speedo pickup tomorrow, assuming the weather is nice (I wish I had a garage). Having to use an oscilloscope is getting way out of my league, not used one of them since college about 20yrs ago, and I didn't know what I was doing with them then!
Norman, I'll get back to you if needed. I want to get this sorted ASAP, before serious driving time starts again.
Mike,
The previous owner put the proper ford expansion bottle on instead of the small one TVR fitted. I never liked that as there didn't appear to be any pressure release capability. So I refitted the normal bottle. When I took that photo which I think is S Slub last year I hadn't managed to remove that bottle due to seized bolts. I've since managed to remove it.
The previous owner put the proper ford expansion bottle on instead of the small one TVR fitted. I never liked that as there didn't appear to be any pressure release capability. So I refitted the normal bottle. When I took that photo which I think is S Slub last year I hadn't managed to remove that bottle due to seized bolts. I've since managed to remove it.
phillpot said:
Hi Russ, bit off subject but what is the plastic "bottle" in your profile photo next to the screenwash ??
I ain't got one of them
First one I've seen too! looks lke another coolant expansion tank... could lead to another huge debate on the location of the pressure cap...I ain't got one of them
Graham
I broke off one of the trimmer resistors on my speedo head whilst trying to calibrate the problem I had away, so had to strip it down to solder in a new one.
The only difficult bit seemed to be getting the black rim off the speedo to get it apart. A large screwdriver and the application of sufficient force
did the trick but wasn't very neat.
Does anyone do Aluminium rims to replace the black ones?
Bob
The only difficult bit seemed to be getting the black rim off the speedo to get it apart. A large screwdriver and the application of sufficient force
did the trick but wasn't very neat.Does anyone do Aluminium rims to replace the black ones?
Bob
Hi Bob,
I've managed to get to the sender by removing the centre console as suggested. Also managed to remove the securing bolt so the sender appears to be free to rotate. As its a bit tight in there (I wish a had smaller hands) does the sender now just pull out or is it screwed in?
Russ
I've managed to get to the sender by removing the centre console as suggested. Also managed to remove the securing bolt so the sender appears to be free to rotate. As its a bit tight in there (I wish a had smaller hands) does the sender now just pull out or is it screwed in?
Russ
Jed-S said:
It does pull out but it is a snug fit.
Yes and it may help to gently rotate it as you pull it up. There's an O ring which can tend to stick it together, but once you get it moving then it comes out okay.Have a cloth handy as it's covered in oil when it comes out and you don't want it getting on your trim.
HTH
Bob
Gassing Station | S Series | Top of Page | What's New | My Stuff