temp and fuel gauge reading low

[abs]

I`m not good with electrics so hopefully someone can help me out as at idle the temp reads normal and the fuel reads OK but as soon as the revs pick up the fuel and temp read very low.
I have changed the regulator behind the speedo a couple of times with no change and checked the earths.
Its a 1967 still running with a dynamo, thanks.

[TECH396]

Have you confirmed that the voltage stabilizer is wired correctly as per markings on the back?
LG =I
G= B

Is the car Pos or Neg earth?

[iain1967s]

It's possible the control box is cutting out too early when the dynamo generated voltage rises from the increased revs.

You can re-calibrate the mechanical switching mechanism, but as you're not 'electrically inclined' an easy fix would be to change it to solid state version.

Mini uses the RB106 spade type: http://www.dynamoregulatorconversions.c ... lators.php

[abs]

Thanks for the suggestions, the car has been changed to negative earth to run an electronic ignition module as the problem existed before that but it`s only annoying me now.
I`ll check the connections as I just copied the existing locations when I changed the regulators and get a friend with a multi-meter to check the cut out power.

[iain1967s]

Test instructions
http://mgaguru.com/mgtech/books/pdf/Luc ... _Tests.pdf

[abs]

Hi all, I still have the gauges reading low when driving at 50 mph.
At idle the temp and fuel gauges will read ok.
So far the control box has been tested and is working fine and the stabilizer has been replaced by a solid state thing that reads a constant 10 volts output regardless of engine revs. The input voltage peaks at just under 16 volts.

I`m stumped

[timmy201]

Do they change if you open or close the windows? I know of some people who have noticed the movement of air past the back of the gauges can affect them

[bwaminispeed]

Having the same problem with an alternator car.........

[abs]

No change with air speed as it will go down whilst holding the revs with the car stationary, the voltage output is bang on 10 volts regardless of revs.

[Dearg1275]

There are two possibilities as to cause. Either there is an increasing resistance ( hard to see how) in the circuit affecting the fuel and temperature gauge or there is an opposing voltage on the earth side. At idle you will have a lower voltage in all the non stabilised circuits and a higher one once the dynamo starts charging. If you have an leak to earth with a high resistance at the lower voltage it will affect your instruments less than at higher one.

You can test if this is happening by disconnecting the dynamo (not an alternator) and run the engine at various revs. This way there is a fairly steady voltage in the circuits.If your instruments remain stable then a leak to earth may be your problem.

D

[abs]

Thanks D, great stuff
I`ll give it a go and if that`s the problem i`ll be asking what an earth leak is

[abs]

Unfortunately disconnecting the dynamo and going for a drive made no difference, as soon as the revs got up the gauges went down.
As for movement of air around the back of the gauges they are sealed in with sound deadening.

I think the bloody thing is possessed

[ChrisM]

Did you sort this?

I was having murders with mine - a '67 Positive earth with a dynamo. No temp reading and a phantom fuel gauge where, you were unsure if it was or was not reading. Did the naughty of 12V direct to gauge - yes they work. Checked voltage and connections - all OK. Bridged out the sensors. Still looked good up at the voltage regulator with >10V showing. I went round and round a few times. Then got in one day and found the wipers, heater fan and indicators had vanished. Fuse was still good, but touching it, I could just make out the faintest sparkle between the fuse end and the terminal in the box. Pulled the fuse, put it back in again. Wipers etc back to life, but still no gauges. So I know there was a problem in there. Using a bit of scotch brite and and screwdriver, I scrubbed up the fuse box connections, popped the fuse back in, and low and behold - I had fuel and temp readings.... High resistance in the circuit.

I am not saying it will cure it, but if you have the old standard fuse box, give it a try - it will take you 30 seconds.

[abs]

Thanks, i`ll give it a go