Ford speedo sensor suitability?

[Rob Walker]

Anyone had any experience of substituting the caterham/claerbont speedo sensor that runs from the 6 speed gearbox with the Ford type that Burtons sell and is also available on that popular auction site? The caterham sensor uses a two wire connection red and green wires and the Ford has three wire black brown and yellow, how did you connect it?  I am aware that the brass top hat fixing needs to be changed to one with a smaller thread.  Thanks Rob

[Jonathan Kay]

How to connect it.

Jonathan

[Rob Walker]

Thanks for that Jonathan,    Do you know if the sensor works satisfactorily  when correctly connected ?  My current Caterham sensor is dead and I have had loads of these fail over the past 20 years and as such would like to try a replacement.  The ford sensor gives 8 pulses per revolution so should in theory work. I bought one some years ago but never got around to trying it and then sold the car, now I find myself in the same predicament.

Cheerio Rob

[Jonathan Kay]

Sorry, I don't have any experience of these.

(Mine's mechanical and original!)

Jonathan

[Rob Walker]

I have looked at the wiring diagram for my car EU2 /2001 onwards and am still confused how to connect the ford sensor.  We have established that the for sensor has 3 wires Yellow/brown-pickup,  Brown -VE and Brown/black +VE .  The Caterham diagram does not indicate what the two wires are Red/blue and Light green, it just shows them going into a block drawn in the speedo.    I presume that the brown could be grounded as its -VE and if the circuit is energized there should be a +VE and that should be the Brown/Black leaving the brown yellow to be connected to the light green.  Can anyone please confirm this?  Thanks Rob

[Jonathan Kay]

Some more clues here.

Jonathan

[revilla]

Funnily enough I've just wired one of these up! You may have seen my post asking about the speedo connector to make a test harness, it was to test precisely this. I also wrote an email to somebody explaining exactly how to wire it up, depending on the wiring in the car which may be one of a couple of different variations. I can convert that into a post on here. Unfortunately, I'm in KFC with the kids so it will have to wait a bit! Get back to you later.

[revilla]

OK I'm back. This is adapted from the email I sent someone after I got my own speedo working with his new Burton sensor on the bench, using a test harness, plus info from my post on the other thread on the speedo connector and pinout:

 

Sensor Brown Wire - This is the sensor earth. A little bit confusing as brown is often used for +12V in the loom, but the brown wire from the sensor is earth. You can either join it into an earth wire in the loom, or you can maybe wire it to the chassis close to the gearbox. NB: NEITHER of the original sensor wires are proper earths, so you can't use one of the existing wires.

 

Sensor Black/Brown Wire - This is the sensor +12V supply. You need to wire this into one of the ignition-switched supply wires on the instrumentation fuse. The easiest thing to do would be to join a wire into the green wire at the back of the speedometer. This is a 12V supply on the correct fuse, so the sensor will be powered when the speedo is powered and off when the speedo is off.

 

Sensor  Yellow / Brown Wire - This is the sensor signal wire. It's a digital output from the electronics inside the sensor. The compatible input pin on the speedo is Pin 6. But this is where things get a bit strange ...

 

Caterham's wiring diagram show the two wires from the original sensor being wired to the speedo on pins 7 (Red/Blue) and 8 (Light Green). But on my car, they are wired to pins 6 (Red/Blue) and 8 (Light Green). I think this was changed with earlier cars being wired as per the diagram and later cars being wired as per my car, possibly with a change of speedo used.

 

If your car has the original Red/Blue wire on pin 7, as shown in the wiring diagram, you will need to add a new pin into the connector at pin 6 and wire the sensor to this, leaving the old Red/Blue wire unused.

 

If however your car has the original Red/Blue wire on pin 6, as on my car and most others I've seen, you can just join the sensor Yellow/Brown wire to the old Red/Blue wire at the gearbox and it should work. 

 

In either case, the old light green wire should be left unused.

 

So ...

 

If your car is wired with the Red/Blue wire on Pin 7 as the wiring diagram shows like this:

 

Then wire the new sensor like this:

 

But if your car is wired with the Red/Blue wire on Pin 6 like my car:

 

The wire the new sensor like this:

 

If you do need to add a pin to the speedo connector, it's a TE/AMP Multilock 040 connector and you need to buy Multilock 040 female terminals suitable for the wire size used. These are suitable for 0.5mm2 wire: https://uk.rs-online.com/web/p/crimp-contacts/7121909 They are rather too small to crimp with a standard uninsulated crimping tool. I use Molex Service Pliers and crimp the conductor at 2.0mm and the insulation at 2.8mm and even then you have to punch the terminal between flat nosed pliers after crimping before it will fit the housing. If you find you need to add a pin and want me to make up a length of wire with a terminal on the end that you can just push into the housing, just let me know. There are two little locking plates that you need to unclip and fold out on the back of the connector before inserting the terminal - I can show you the details if you need them.

If you wanted to avoid having to run an additional 12V supply wire down to the gearbox sensor location, you could cut the original (no longer used)  light green wire off at the speedo connector and join the cut end into the (dark) green supply wire to the speedo; you would then use the original light green wire at the gearbox sensor as the +12V feed. It just depends on how you feel about chopping the old wiring, whether you want to be able to go back to a standard sensor at some point etc.

Hope that helps.

Andrew

 

[Jonathan Kay]

Images not showing but still magnificent.

Jonathan

PS: Do the family make chip jokes in KFC?

[revilla]

Hopefully the images are fixed now. I'd copied and pasted from the email and ended up with image links to images in my gmail account; they worked for me as I was logged in to my email account but probably (hopefully!) wouldn't for other people.

I'm not sure what level of sophistication you expect from my little girls in the humour department - I'm afraid they're at the stage where they find "chicken balls" hilarious!

[Jonathan Kay]

Four images now showing inline.

Jonathan

[Rob Walker]

Thanks Jonathon and Andrew, for a very comprehensive reply, very helpful, I should have no problem with this information excellent.

Cheerio Rob