Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Speedometer reading SLOW on Plus 4 2013

Returning home on Monday by motorways and A roads I became aware that the speedo appeared to be reading significantly SLOW. I checked against my GPS satnav and confirmed the speedo was reading a constant 9mph slower than the GPS. Even noticed. This error was constant for various speed between 30mph and 70mph for a good 20 miles. I stopped and restarted the engine and the speedo corrected itself to around 2mph above the GPS reading which I guess is about right.
Has anybody else experienced this? Its easy to spot a 9mph error but if it was 5mph I may miss it but the ugly yellow box on the lamppost would not. It's never happened before although the rev counter sometimes sticks at idle revs when I turn off the ignition.
"But honest officer the speedo said 30......"

I have experienced this issue more than ones. Keep her some time to recalibrate herself. My car is fitted with a main battery switch because my garage provides no current. After reconnecting the battery everything is ok.

My 2013 4/4 has read 8kph slow at 100kph since day one.

On the delivery drive back from Melbourne I realised I was the fastest thing on the motorway and the gong on the satnav kept warning me I was speeding too.

The dealer gave the garage that performs warranty work a set of codes but this has made no difference.

Others tell me its normal. I'm getting used to hearing that!

I presume that you all have electronic programable speedos from VDO as i do .
When i first picked up my car the speedo was very erratic , sometimes fast by as much as 20 kph and sometimes slow . Totaly random and no amount of resetting with the ign switch or the battery master made any difference .
I checked wiring connections and made sure i had a full 12 v and a good ground then recalbrated as per VDO instructions i found on the web ,all to no avail . I also noticed that the speedo head had been replaced twice for the same issue before i bought the car .
I concluded that i was getting a "dirty" signal from the speed sensor so i added a capacitor to the signal connection on the back of the instrument and recalibrated .
Now its deadly accurate and hasnt missbehaved in any way for the last 15 months and probably 5000kms .
The capacitor i used was just an old condenser from an old distriburor i had lying around , but one should be avaliable for very little money from any parts source and they are all the same essentialy .
Worth a try i would think for a couple of pounds and 10 min work ?

Dave, I assume the capacitor is in line, it's an electrolytic cap. Any minimum value of Farad? or just try what is lying around to get HF filtered out?

Don't know if this helps but I saved it in my 'information' file......It relates to resetting the calibration for an 09 +4 and I don't know if much has changed before the build of your car?

The code for an 09 Plus 4 is 008386, assuming there is not more than 1 version of the milometer in use at the time. To operate, press in the ‘trip’ button under the dash while starting the car and using the button set each number in sequence as it flashes in the milometer. Allow it to revert back to the milometer reading and all should be well.

Thanks for your input so far guys it's really useful. I should have added my speedometer is a SMITHS clock which pretends to be an old mechanical chronometer by jumping up and down by a couple of mph at a time as you accelerate and decelerate.
I'm a bit nervous about using Spanner Juggler's calibration code in case it's incorrect for my device and throws the readings out completely. Can anyone confirm it's the correct code for a 2013 Plus 4?

Now you have given us that extra information I would say its definitely not to be tried, the recalibration process is for the VDO instrument. You can try the factory but good luck getting anyone to reply.

It's unlikely to be that straightforward (well, it is a Morgan...)

The code is the pulse calibration value that 'tells' the instrument ECU how many pulses equate to 1 unit of distance.

It certainly varies with wheel/tyre combinations (ie rolling circumference) so the Factory use different codes depending on the configuration of a particular car.

Also, it used to be the case that some models took the signal from a front hub and some from the final drive. From memory, a Plus 4 has a Hall Sender taking a signal off the back of the nearside front hub. Worth checking if it is out of alignment.

Lastly, if you do decide to input a different value, the display initially shows the current value - so write this down and you can always restore it if a new value doesn't solve your issue.

Can't remember the name but there is a clock specialist in S. Wales (someone will come up with the name shortly!) who have been recommended on this forum in the past.
Best discuss things with them...