Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Hub/Stub Axle mounted speed sensor replacement

Post PhotoBucket update from Flickr..........

The speed sensor on my 2005 Roadster is on the gearbox output flange, so is quite difficult to access. At some point before 2012, it was moved to the right hand/offside stub axle.

This leads on from my Kingpin thread, but is worthy of its own thread. I removed the speed sensor from the stub axle when I replaced the bushes, because its a fragile looking item, and may have been damaged during that process. What I hadn't realised was the real fragility of this component. The unit is an 8mm fine thread stud which has been drilled down the centre, and what results is a very thin walled stud with limited strength. Inside is the electronics in a resin base. What happened when I refitted the stud, and 'nipped' the nut (and not very tight I might add) - was that the thread split and in doing so, cracked the resin inside and broke the circuit..............

IMG_5529 by David Wellings, on Flickr

This is how it goes together - the plug has three waterproof plugs in the end, and the cable runs through the cable protector shown here.

IMG_5531 by David Wellings, on Flickr

Ignore the blue blob on the end here. I was thinking about using that to set the gap but didn't use it in the end.

IMG_5544 by David Wellings, on Flickr

The obvious route to locate a new sensor was a Morgan Dealer, BUT - given my recent experience when I tried to get some brake pad pins and springs, the likely reaction would be that it would need a factory order and that would take time. My experience of factory orders in the past have been that you should expect a "number of weeks". This is something that both MMC and the dealers need to do something about, because the delays are not acceptable.

So a quick look on the internet revealed that the sensor is Revotec, and is available from a number of suppliers from stock. I placed an order with Demon Tweeks and received the sensor in three days. I also had to source a new weatherproof plug, as the original was in less than good condition. The sensor comes with two nuts, the idea being that it can be fitted on a bracket. I wondered why MMC had only used a nut on the outside and threaded the stub axle.........

IMG_5541 by David Wellings, on Flickr

IMG_5542 by David Wellings, on Flickr

You'll note from the instructions that a gap of no more than 2mm is required, so in order to establish how far to screw the sensor in I first took a thinner bolt and used the nut as a stop, pushed it through the hole and adjusted it until it just contacted the bolt heads.
The required length from the back of the stub axle is 18mm.

IMG_5546 by David Wellings, on Flickr

In order to give a 1mm gap, I set the nut at 17mm - so...

IMG_5547 by David Wellings, on Flickr

BUT, on refitting, I found the reason that MMC don't use a nut at the rear - the nut fouls the stub axle..........

IMG_5550 by David Wellings, on Flickr

So I recalculated the gap from the outer edge of the stub axle, 9mm is required. I refitted the stud, and the outer nut was secured with Locktite.

Before doing that I had cut the cable to the right length and fitted the plug.

IMG_5543 by David Wellings, on Flickr

I also had to change the plug on the loom......

IMG_5548 by David Wellings, on Flickr

This is a waterproof plug with a tight sealing grommet in the end.

IMG_5549 by David Wellings, on Flickr

The loom colours are yellow; yellow/black trace; and green.
The sensor colours are brown; black; blue.

The matches are:
brown to green - 12v +ve fused switched supply
black to yellow - 12v -ve supply
blue to yellow/black - signal to instrument - white/black on speedo

The next job was to refit the hub, and by rotating the disc, that the sensor LED was flashing...........so generating a signal

IMG_5552 by David Wellings, on Flickr

I then put the wheel on temporarily, put a mirror & torch on the back of the seat, and checked the the speedo responded - it did! It was easiest to see with the garage lights off, and sidelamps on.

IMG_5553 by David Wellings, on Flickr

I could get enough momentum to be able to walk round and check that the speedo was working properly

IMG_5554 by David Wellings, on Flickr

All that was left to do was to shrink some wrap over the sensor end of the cable, and tie it up out of the way.

IMG_5551 by David Wellings, on Flickr

These are the bolt head sensors on the hub......

IMG_5368 by David Wellings, on Flickr

And that's two fingers to Photobucket.

Yeh..photobucket Nil ...DaveW 10!

And another fantastic post from the Guru!

Well done Dave. Glad to hear my 2006 car probably doesn't have this.

Thanks Dave, much appreciated!

Hi
I just found this thread and it's made me think.
The speedo sensor on my 4/4 Zetec MT75 has packed up and its a devil to get to it being tucked up the side of the gearbox inside the gearbox cover. Not impossible but I was looking for a better way when I found this thread.
My question is whether this Hub/Stub axle mounted sensor system is a regular way of doing it on newer Morgans or was it just a one off on Dave's car.
My stub axle does not have the drilling but it would be easy enough to modify and then mount the Revotec Hall Effect Sensor and wire direct to the VDO speedo.
If it was a one off, I'll probably stick with the standard system but if this is a newer way of driving the speedo I might give it a try.

Bob, the hub mounted speedo has been standard for several years.

Thanks Dave, I'll go down that route.
Is the hub mounted speedo standard on all models now? Trads at least.

All the Trads Bob. Don't know about the Aeros.

Mine is gearbox mounted, Dave. Certainly only a blank hole in the hub anyway..

I wasn't going to let you know until the re-print..

That is probably just the current Roadster then with the can bus wiring..........

This is exactly why trying to be definitive about Morgan history is impossible. If Morgan find a part at the back of a shelf, it will be used on the next car. That's how it works!!!!