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MG MGB Technical - Instrument Panel Fluctuation

Given my continuous search for answers to my many electrical questions, I realize I've never mentioned this little issue about my 72 B.

So in addition to my car's random hiccup while cruising along that jerks the car for a split second. And the 2-3 hiccups when I shift into overdrive. And the 1-2 backfire when driving away with a cold engine (clears up by pulling choke out just a hair), I have made the following observation:

When I start the car (cold) the gauges on the dash bounce or vibrate. This is most noticeable with the temp gauge but it also occurs with the tach, oil pressure, etc. It is the temp gauge that is most confusing for an explanation. Car fires right up and idles fine, but when looking at temp gauge especially the needle is bouncing or vibrating 1/4" or more - this continues until the car is warmed up, then all the gauge needles set still.

Why would the needles in the gauges be vibrating so much? Is this the sign of more negative ground or connection problems?

Thanks for your assistance.
R.W Anderson

RW - The condition you describe is probably nothing more than the gauge needles vibrating. The fuel gauge in our MGB does the same thing when it is first started and is running with the choke on. This is pretty much the nature of these gauges and once the choke is off and the is warmed up and running smoothly, the needles settle out. Cheers - Dave
David DuBois

The needles on your gauges move? Must be nice!!!!

-Frank
Frank

I have to tap on the glass of the tacho to get it working, or rev the knackers off the engine, which I dont do when the engines cold. I consider it an idiosyncracy of having a classic car and it doesnt really bother me. Maybe when Im on top of all the other jobs in my car Ill open it up and get it sorted out, but Im not nothered at the moment. Its the first car Ive ever had with a tacho anyway!
Ross Kelly

Remove the glass from the tach and put a spot of silicon grease on the little post that the needle rests against when off. The needle could be sticking to the post.
Sandy
conrad sanders

That might well be it. I'll give that a go some time. Ive got some silver tape as well to line the inside of the case with as well to increase the brightness so I might do that in the process.
Ross Kelly

Ross, the tach in my temporary little instrument panels does that. Have to tap the glass to get it moving. And it is actually the second one to do that! The first one I had did that also but then I sent that one away to someone who needed it for their car.

I have brand new instruments I will be using in my finished car so it doesn't bother me too much.

SImon

Simon
Simon Jansen

lol. Maybe its a feature of them. You might find the new one does that too! :)
Ross Kelly

The electric fuel and temp gauges at least are thermal types and as such are only capable of moving at a snail's pace under electrical changes. Any 'vibration' of the needle you can see can only be due to mechanical vibration from the engine, which will also affect the other gauges.
Paul Hunt

This thread was discussed between 24/06/2008 and 27/06/2008

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