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MG MGB Technical - Dual oil pressure / water temperature gauge

Would really appreciate some advice;

Garage just removed the centre console of my 1969 mgc roadster to fit a 12v socket, and on return home found water temperature part of the dual water temp. / oil pressure gauge has frozen.

The fact that only part of this dual gauge appears to have failed could be a loose wire connection, or is it more likely that the dual gauge has failed and should be replaced?

If I must buy a replacement gauge, is it best to buy a Smiths gauge or are the aftermarket ones any good?

Thanks for any help
JP Mitchell

I'd have thought the temp part wasn't electrical but on a capillary(?) tube, looks like a thin copper tube with wire spiralled around the outside

so have look to see if they've damaged or squashed that pipe not knowing what is was
Nigel Atkins

I agree, a 1969 car would (should) have a capillary temp gauge, and a mechanical oil gauge too. The only electrical bit of the dual gauge would be the lamp inside.

If the capillary pipe has been damaged, the temp gauge is stuffed as they say, and cannot be repaired by you. Either send the gauge to Speedy Cables for repair, or buy a new one, which almost certainly will have been made by Speedy Cables who have the manufacturing rights for Smiths instruments. These gauges aren't cheap to buy or repair.
Mike Howlett

HOME REPAIRS can be done. Look in the archives and there are instructions to repair and recharge..
ss sanders

The best Princess i have found for These dual Mechanisator Ganges is

If your gauge is Toast, I am looking for a broken one to obtain a smiths face, either in Fahrenheit or Celsius. I have a good gauge with a jaeger face that does not match the rest of the dash! and want to switch the face over
Dominic Clancy

When you say 'frozen' do you mean it doesn't rise off the minimum or is stuck at some other value?

If the former it sounds like they have contrived to bugger the capillary tube, which should have been easy to avoid if only working on the centre console.

Is there an aftermarket dual gauge? I would have thought it best to stick to an original from one of the usual suspects. They used to be exchange, but don't seem to be now.
Paul Hunt

will your gauge fit my Twin Cam?
If yes, I have a brand new Smith gauge to change.


Many thanks for all your replies.

The gauge is stuck at the 6.30 position. It did rise just a little on the drive home from the garage but then returned to the 6.30 spot. The following morning on a cold engine, it was still there.
The garage advise it is broken and no choice but to change, being careful to check whether it was C or F.

Perhaps I will learn more when it is removed and will follow up here. Thanks again to all
JP Mitchell

"The garage advise it is broken"

Did they advise how it was broken?
Dave O'Neill2

Hi Siggi

Yes the face will fit. I only want the face because the gauge does work bit does not return back to 0 on the temp scale. It is easy enough to remove the face on any gauge. perhaps you can mail me offline

Dominic Clancy

Stuck at 6:30 i.e. over the N says to me the mechanism has become jammed somehow. Rising a little from there on the drive home tends to confirm it, i.e. if the temp got above N for any reason. If the fluid leaks out from a fractured pipe they won't rise off zero.

OTOH it could be a combination of the fluid mostly leaked out, and the gears having jumped teeth, but that seems unlikely.

Remove carefully - or disconnect the oil pipe and feed the loops of capillary through the bulkhead so you can ease the gauge forwards from the dash without removing the sender from the head - and open up, you may be able to fix it.

Typical internals can be seen here, this is a single gauge off another vehicle, the dual gauge is similar but has two lots of the mechanism of course. There is only a tiny amount of movement in the levers to cause the needle to swing from zero to max, so it follows that not much of an obstruction or misalignment will stop it returning to zero.

I'd also be interested to hear what the garage say about 'how'.
Paul Hunt

Does anyone have any experience of electrical vs capillary gauges? If not concerned about originality, and if having space for an extra gauge, it seems much more sensible to have electrical sensors as they are more robust, spares can be obtained and a they are lot cheaper to buy. I was planning to convert when mine fails as I am sure it will at some point from past experience. are there downsides to electrical temp/pressure gauges? hard to think of any.
Graham Moore

downsides of electrical are possible compatibility possible issues of sender to gauge, possibly poor modern build quality of senders - but I don't know that to be so for certain

capillary (oil pressure at least) I'm told are generally more accurate - but I don't know that for certain

if your present gauges go wrong you yourself may be able to repair or recalibrate them

save your money for what needs servicing on the car now and maintain and repairing in the near or medium future
Nigel Atkins

I presume you are talking about the dual oil/temp gauge. Are the electrical versions of those? If not - and the factory only used single gauges where electric versions were used, you would need an extra hole for the same number of instruments.

Compatibility of gauge to sender that Nigel mentions is a factor, there were at least two types used on the MGB for temperature and getting them mixed up causes incorrect readings, for example.

Electric oil gauges are best avoided, they were only used for a relatively short period on the MGB before they reverted to a pressure gauge.

Accuracy is as suspect with either type these days. The dual gauge is not really repairable at home, especially the temp section, but you are likely to pay about the same for a pair of separate oil and temp gauges as one dual gauge, plus about the same as the gauge for the electric oil sender.
Paul Hunt

This thread was discussed between 19/03/2014 and 13/04/2014

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