Morris Minor Owners Club

To the good and noble people of the MMOC,
I appear to have an interesting problem with my voltage stabiliser. I have been having problems with my fuel guage for a while now and I believe I have traced it to the voltage stabiliser. When I send a current through the stabiliser without it being earthed to the car or connected to the speedo it shows a voltage reading of 12.47 or there abouts, which I'd expect. When I then connect the stabiliser to the speedo or any part of the dash the voltage is lost. Is this intentional or do I have a duff voltage stabiliser? Please see pics for my method and voltage readings.
Any advice is always greatfully received, many thanks,
Tom

As I recall, most were 10.5 Volts output. As such, you should not see battery voltage (which is what I suspect you are reading).

I have the same problem and have done for a few years now ever since I took the speedo out for a check on the cable and laid the clock on the edge of the orifice with the ignition still on. It blew a fuse so things like the indicators etc. didn't work so the fuse was changed, everything else came back to life and the gauge ever since only shows the tanks at 50% capacity. i.e. if I fill her up she shows half full. If she's 3/4 of a tanks she shows 1/4 etc. ! btw she's on an alternator so negative earth if this makes a difference .

I believe the case of the voltage stabiliser has to be earthed , and if you have a fancy electronic one you can't mix positive and negative earth ones.

John

Here is a link to change it to an electronic version if required.
http://www.britishv8.org/articles/mgb-v ... ilizer.htm

Does sound like a duff stabiliser but that type produces pulses between 12v and 0v which averages out to about 10v. This could confuse a modern LCD multimeter, best measured with an old moving coil meter. Seeing as you get next to no output from the stabiliser with your meter you could confirm this by removing the wire on the “I” terminal and connect a small 12v dash type bulb or test light between the ”I” terminal and earth and it should light slightly dimmer than with 12 v. If it doesn’t light then that confirms a duff stabiliser. As you say the stabiliser has to be earthed.
Regards John

Thank you everyone for your swift replies, I will try the method you suggest to test a duff stabiliser. I'm glad to hear I'm not the only one to experience a stabiliser issue. What would be the cause of a stabiliser malfunctioning?
Many thanks,
Tom

A stabiliser, like any electrical component, can fail at any time and for no reason, although accidental damage (a short whilst working behind the speedo, or a stray wire) certainly won't do it any good! The one on my dynamo-charged Marina failed some years ago over a period of about a month, with the temperature and fuel gauges gradually giving much lower readings at idle than when being driven, before finally failing completely with both gauge barely moving off their stop-pins.

Forgot to say but you may realise that it has to be the right way up, has Top marked on it.
This is because it uses heat to warm a bimetallic strip so needs to be above the element this also means when first powered up will give full battery voltage until the bimetal strip heats up. I’m not sure how long that takes.
As for cause as Palacebear says, but if it is faulty it does have a set of contacts which if you can successfully open the unit might be worth cleaning, you never know your luck!
If you replace it with the same type it doesn’t matter whether the car is pos or neg earth.
If you go the electronic route you need the correct one.
Regards John

Thank you all for the helpful advice. I'm always loath to acquire new parts when old ones have a chance of being salvaged. If the stabiliser does prove to be a duff is there a way to fix this device, I don't hold out too much hope as it seems like a single contained unit but you never know!
I may of just answered my own question after reading your supplied link. I will do a bit of tweaking and let you all know.
Cheers,
Tom

If you take it apart,there is a V. slight chance you can clean the contacts up but more likely they're burnt beyond repair.

John

As 'stillgotmy1stcar' and 'sleeper' have suggested, it may be repairable IF you can open it up. It's not designed to be maintainable so you may well have no luck. New 'pattern' replacements are about £15. I can't comment on the quality but maybe someone else who can, will be along shortly and contribute

After a lot of failed attempts I've finally caved in and found a second hand stabiliser online. Thank you all for your suggests, annoying that this part seems to have such a certain eventual failure. But hey, problem solved! All dials now... working
Cheers,
Tom