Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 M3W Speed Sensor E340022 Discontinued

I recently found out that MMC appear to have discontinued the speed sensor that is fitted to the M3W (5-Speeder) and +4 Duratec.



On the M3W, this sensor is fitted through the right hand front brake calliper bracket. As the hub rotates, five bolt heads pass closely by the head of the sensor, thus creating 5 pulses per rotation and this signal is subsequently converted into the speedo reading.

MMC have superseded the sensor with this type:



It’s MMC part number E221002 and as you can see it is quite different to the original one, having an integral socket. To compound the problem, the original loom connector needs replacing as it isn’t compatible with the new sensor.

I therefore set about making a replica of the original type. This has a 5 Inch (125mm) lead leading to an Econoseal plug, with a ‘pull-up’ resistor between the sensor output signal and +5V.



Once I had sourced the components and the special crimping tool needed for the connector pins, I assembled the assembly with a suitable amount of heat-shrink sleeving to make it as waterproof as possible. I have to say that it was a bit of a fiddle, especially having to incorporate the resistor into the plug.

I’ve often thought that having the sensor connector adjacent to the lower wishbone where it is guaranteed to be exposed to copious amount of water and muck from the road is not one of Morgan’s most inspired decisions (and doesn’t look particularly attractive either). Indeed, when I took my original connector apart, there was evidence of corrosion on the pins, even though the connectors are nominally waterproof.

Therefore, I am also making up a long-lead version of the speed sensor which has a 1 Metre lead. Once the existing loom has been unclipped from the lower wishbone, it can be fed back up to the area below / in front of the oil tank, adjacent to the red +12V post. The lead from the ‘long’ sensor is then run along the lower wishbone and fed up behind the chassis tubes to the new connector position. The plug, socket and ‘spare’ cable can then be tucked under the transverse chassis tube and held in place with a couple of tie-wraps. Obviously, this is a bit more involved to fit but does result in a much neater installation and a more appropriate position for the electrical connector.

When I removed the original sensor from my car, there were witness marks on the sensor head where it had come into contact with one or more of the hub bolts.



The sensor spec calls for a clearance of 0.3 – 2.3mm between the sensor and trigger so I sourced a 1mm thick shim washer which can be fitted between the sensor mounting flange and the brake calliper bracket to increase the clearance if necessary.

The original sensor retaining screw is a button-head type, needing a 5mm hex key to release. Mine was quite corroded so I replaced it with a stainless steel cap-head type requiring a 6mm hex key. This should make it easier to remove in the future if it ever needs to be replaced again.

This is the 'short-lead' kit:



The ‘long -lead’ kit is similar. However, in order to release the loom from the lower wishbone, three P-clips need to be removed. Therefore, this kit also includes 3 replacement black pop rivets for reattaching those clips as well as some tie-wraps to finish off the installation.

If anyone is interested in one or other of these sensors then please PM me as I’m going into limited production! These are listed in the ‘For Sale & Wanted’ forum HERE.

I have fitted the first "customer trial fit" version of the, "Bunny Wheel Speed Sensor" and it all works perfectly. I had not had a problem with the wheel speed sensor in my 11 years of ownership but on taking it apart to fit the new sensor I found the connecting Econoseal plug was not as waterproof as it should be and the pins were a bit corroded, I may have been on borrowed time! I also found that the clearance to the trigger bolt tails was nil and the sensor had some score marks, the spacer washer supplied with the new sensor fixed this.

Replacement was simple with the connecting plug now located near the battery post and clipped to the chassis tube, well out of the way of any water. This is a worthwhile modification and certainly worth doing if you have any speedo problems, they are usually related to the connecting plug. The wheel speed sensor does speedo indications but also has inputs to the indicators and engine idle speed mapping, so an important sensor that will cause issues if not working correctly.

Quite why MMC would market a replacement item that doesn't fit or work.......

Calling owners of later M3Ws! I would be very interested to know if your car is fitted with the original or later type speed sensor. I'm thinking the change was probably made after 2019 - but am not sure.

Thanks to some valuable feedback, I've now been made aware that there have been (at least) three different speed sensors fitted to the X-Wedge M3W!

I'm still interested to know what type of sensor is fitted to your car (referenced to your car's date of manufacture).

I'll do some testing to ascertain whether E340110 is a direct replacement for E340022, i.e. whether MMC decided that the pull-up resistor wasn't necessary...

Onwards and upwards!

Seeing as we’re pretty much house-bound at the moment and there’s nothing on the telly, I decided to let my mind wander a bit regarding why MMC might have deleted the pull-up resistor from the M3W speed sensor.
The speed sensor used (Honeywell 1GT101) is primarily designed as a gear tooth sensor.

In this application the triggering frequency will be much higher than in the M3W. Indeed, the sensor is specified to go up to 10kHz, i.e. 10,000 triggerings per second!
A back of the envelope calculation indicates that, even at 110 miles per hour, the speed sensor will only be working at 111Hz, i.e. 111 times per second. (It is linear, so at 80mph there are roughly 81 sensor pulses per second.)
The purpose of a pull-up resistor is to ‘reset’ the sensor output between pulses. This is probably desirable at 10kHz but not really necessary at 111Hz.
In addition, omitting the resistor will have simplified the production of the sensor assembly by MMC’s supplier which may have saved a few pennies.
All just my ramblings of course but I have verified that the speedo works fine on my car with or without the pull-up resistor. Therefore, I plan to omit the resistor from future ‘Bunny’ speed sensor assemblies I make.
Right, everyone can wake up now!

Andy - we have a v early (April 2012) M3W and we therefore presume it has the original the 12 pin TSM which takes an input from the speed sensor. Not sure whether your car tested without the pull up resistor has the 12 pin TSM or the later/more common 18 pin version.....

Is there any indication from your interactions with Alister W that the pull up resistor might have been needed for this early TSM but perhaps not required (but left in) for the later 18pin TSM???

If required, we are happy to be guinea pigs on this with the one we have ordered from you (if of course you have not already tried without the pull up resistor on both types of TSM....)

Yes, my M3W is only a little younger than yours (June 2012) so has the 12-pin TSM. It originally had the sensor with pull-up resistor but also seems to work fine with the later type that doesn't have the resistor. I'm not sure when MMC started to use the sensor sans resistor as standard, but it was certainly before late 2019 when the 18-pin TSM would have been fitted.
I did check with Alister and he confirmed that the 18-pin TSM does not include a pull-up resistor.
I'll send you a PM about what sensor I send you!

Thanks for clarifying this Andy

Hi Bunny - my March 2020 build M3W appears to have the E221002 variant. (It was one of the last cars built before the Covid shutdown)
Here's a picture:

Another complication! It seems that early 2012 cars have their sensors held in place by M8 bolts. My car is June 2012 and uses a M6 bolt, so it looks as if the M8 mounting was short lived. It's not a big deal to file out the mounting hole in a replacement sensor to 8mm but is something to be aware of. By the way, don't attempt to drill out the hole in the sensor to 8mm as you'll find the metal insert just spins in the plastic housing.

I'd be glad to hear if anyone has a car later than mid 2012 that also has the M8 mounting bolt even though it would prove my theory wrong!