Morris Minor Owners Club

I have noticed that the petrol and temp gauges read over on my Traveller but that when the car returns to tick over, they read what I believe to be right. Before I condemn the voltage stabiliser, I thought I should check the control box.

It's years since I last did so (Though not that many miles have passed) and my memory is a tad rusty. The workshop manual tells me to remove the wires from terminals A and A1 and connect them all together. I can't remember whether that means ALL (I think it does) of them or just the two larger ones at the front. A1 is the one on the left of the attached and A, the next one to it. It then tells me to connect the negative of the voltmeter to D and the positive to E and it gives recommended readings of between 15.8 and 16.7 volts, depending on ambient temperature.

Surely you mean volts not amps and the connections of the meter will depend on negative or positive earth car.

Yes it was a typo but I was also reading an item, which mentioned checking the amperage between the battery terminals, with the lights turned on and the engine running at 3000 rpm. Doing some further searches for this revealed http://morrisminorowners.co.uk/viewtopic.php?t=5040. I said my memory was rusty . Will print that off now and put in the manual.

The instrument voltage stabiliser on the back of the speedo is designed to give an output of 10 volts to the fuel gauge (later cars). If it isn't working properly then the instruments will be subject to voltage variation in response to dynamo output which of course is engine rev dependent. This would appear to be exactly what is happening in your case. The original instrument voltage regulators are electromechanical devices and they do go wrong after a long service life. The modern replacements are solid-state electronic and they are polarity sensitive so get the correct one (positive OR negative earth). Note that the instrument voltage stabiliser can only supply 3 instruments of which the fuel gauge is 1 of those instruments.

It is generally not considered a good idea to fiddle with the calibration of the RB106 unless it is known to be faulty.

Stephen

Personally I find the details in the Workshop Manual far too complex.

All those temperatures and a note about doing things within 30 seconds.....

This 1963 Lucas Booklet is much easier to follow https://www.mg-cars.org.uk/imgytr/pdf/lucas.pdf

Note the info given on the inside page.... As has already been mentioned, the Minor manual is written for a Pos Earth vehicle.

This Lucas Booklet includes a useful detail

"When vehicle has a positive ground system, positive meter lead must be grounded."

It's a 28 page booklet, but that is to cover all the various Control Boxes. Only pages 3-9 are required to check the RB106.

[quote=svenedin post_id=719058 time=1779264855 user_id=21995]
The instrument voltage stabiliser on the back of the speedo is designed to give an output of 10 volts to the fuel gauge (later cars). If it isn't working properly then the instruments will be subject to voltage variation in response to dynamo output which of course is engine rev dependent. This would appear to be exactly what is happening in your case. The original instrument voltage regulators are electromechanical devices and they do go wrong after a long service life. The modern replacements are solid-state electronic and they are polarity sensitive so get the correct one (positive OR negative earth). Note that the instrument voltage stabiliser can only supply 3 instruments of which the fuel gauge is 1 of those instruments.

It is generally not considered a good idea to fiddle with the calibration of the RB106 unless it is known to be faulty.

Stephen
[/quote]

Oddly enough, it's the new ones that seem to be giving most trouble. I have only the fuel gauge and temperature gauge running from my voltage stabiliser. I prefer the capillary type temperature gauges (Which are sometimes combined with an oil pressure gauge) but my car came with a pair of extra gauges, of the type that I had had on Minis in the past and they never gave trouble

geoberni wrote: ↑Wed May 20, 2026 11:32 am Personally I find the details in the Workshop Manual far too complex.

All those temperatures and a note about doing things within 30 seconds.....

This 1963 Lucas Booklet is much easier to follow https://www.mg-cars.org.uk/imgytr/pdf/lucas.pdf

Note the info given on the inside page....
Lucas Booklet.JPG

As has already been mentioned, the Minor manual is written for a Pos Earth vehicle.

This Lucas Booklet includes a useful detail

"When vehicle has a positive ground system, positive meter lead must be grounded."

It's a 28 page booklet, but that is to cover all the various Control Boxes. Only pages 3-9 are required to check the RB106.

Downloaded

Could it be your fuel gauge is 10v and should be running off the stabiliser but your after market temp gauge is a 12v and should be running direct off battery voltage.
Just an idea?

The temperature and oil gauges were supplied used to the previous owner and were out of a Mini. In Minis they sat either side of a Minor type speedo. In my car, both the temp and fuel gauges are affected equally.

Blaketon wrote: ↑Sat May 23, 2026 12:06 am The temperature and oil gauges were supplied used to the previous owner and were out of a Mini. In Minis they sat either side of a Minor type speedo. In my car, both the temp and fuel gauges are affected equally.

If you disconnect the temp and see if you still have the issue with the fuel gauge which is original.

It's only since I've been using Caerbont stabilizers that there has been a problem. Until the OE unit packed up, both gauges were fine (Now both are equally affected). I have a spare, unused Caerbont stabiliser (So I gather, all the new ones sold are theirs; don't know if they make them or whether they are made in China) and may try that BUT I have found a place, who make replacement ones from better quality parts, so that may be a better bet.

Blaketon wrote: ↑Sun May 24, 2026 9:24 pm It's only since I've been using Caerbont stabilizers that there has been a problem. Until the OE unit packed up, both gauges were fine (Now both are equally affected). I have a spare, unused Caerbont stabiliser (So I gather, all the new ones sold are theirs; don't know if they make them or whether they are made in China) and may try that BUT I have found a place, who make replacement ones from better quality parts, so that may be a better bet.

Maybe get an original. They can be found new old stock.

Stephen