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MG Midget and Sprite Technical - Do Instruments Have Memories!?

I have a 1275 midget that was unused for c2 years. I serviced it and did what was necessary, new battery, hoses etc and it passed the MOT about a month go. When I first used it the petrol gauge read very low - it has always under read but previously a full tank read between 3/4 and full; since MOT until yesterday a full tank read just over half full. Similarly, the rev. counter would not go above 3000 RPM even when I am sure the engine was turning at 4000+. This has been the caee for the 400 miles since MOT. Oil pressure and water temperature gauges seem to be operating the way I remenber them as does the speedo. Yesterday evening I took advantage of good weather and went out for a run. I immediately noticed the fuel gauge was showing nearly full, i.e. back to how it was two tears ago. This made me take particular notice of the rev. counter which seemed to be much more accurate although I feel it is still reading slightly low especially towards the top end. I also noticed an occasional, almost instant, drop from 3000 to 2500 RPM. I am confused. Could the infamous voltage stabiliser cause this effect? Should I leave well alone and hope for more improvement with further use of the car?

Thanks, Ray
Ray Rowsell

Demon possession possibly....???? Haha

With my recent adventures into fuel, is say the fuel gauge sender is tarnished ..... With the new fuels over the past 2-3 Years they seem to have a life span of 6 - 8 weeks

This is just a guess as I've never dealt with the fuel sender before.....I don't think and not sure if the each utilizes the voltage stablizer or not....but they are not known for there digital accuracy....could be the wrong tach from a previous owner replacement

All in all, sounds like you have a great car ..... Keep enjoying the days of what's left of summer


Voltage stabiliser is only for electrical fuel and temperature guages, nothing to do with the tacho.
Cheers John

probably be electrical connections (including earths)

not using it for 2 years will have done it no favours, the more you use it the better it will get but you will need all electrical connections to be clean, secure and protected

including voltage stabiliser, coil ect.
Nigel At

Thanks for your thoughts.

John, I appreciate the info.
Nigel, I agree lack of use has not helped. I am now using it regularly and enjoying it enormously. I believe, as long as the basics are sorted; oil, water, grease etc. the best form of maintenance is use, so I intend to do plenty of "maintenance" before the Summer draws to a close. Hopefully, by then, my enthusiasm will have fully returned and I will return to being an all year round Midget driver. In the meantime I will watch for further improvement in the instrument's accuracy.

Regards, Ray
Ray Rowsell

Yeap I agree the cars are for driving, that's the only bit I enjoy

if the car's had full and proper servicing, maintenance and repairs then there'll be more driving of it as it'll run more and better

the more you drive it the quicker the niggles dissappear
Nigel At

Oil pressure and water temp are mechanical gauges; all the others are electric, which suggests problems with electrical contacts (external most likely, but also internal is a possibility).

Additionally, dont' forget the fuel gauge is driven by an arm (operating a variable resistor) that floats on the fuel courtesy of a ... float. The float is a small plastic barrel; they can become porous, have cracks and so on, and can give anomalous readings.

Instruments don't have a memory of any kind... AFAIAA...

Anthony Cutler

Speaking of, Every midget I have owned or worked on had a tachometer that wouldnt register apon start up unless I bliped the throttle or rev the engine. I always wondering if this was normal, or if this was due to bad grounding. I placed a higher-output alternator in one car, that tach seemed to activate quicker... maybe just my imagination, there probably was no connection between the two.

What is consensus on that?
Ron Koenig

I have to tap mine to get it working otherwise when I pull off it it bounces round to 5,000

it did work straight away for a short period then stopped again, I can't think what was different during that time

it wasn't fitting a higher output alternator though as I done that and it was still the same
Nigel At

I Never had a problem either with a dynamo, or when I swapped to an alternator.

The tacho should register straight away. If it doesn't then I reckon either there is a fault in the Tacho, or a poor connection to it.

If you tap it and it works, then clearly it's a weak connection somewhere. Could be either an earth or the live feed or even the lt ignition loop at the back of the Tacho.
Lawrence Slater

I've had to tap mine for years; it's part of the cars character... doesn't affect its accuracy...

Anthony Cutler

This thread was discussed between 21/08/2011 and 25/08/2011

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