Classic car GAUGE RESTORATION - Repairing the gauges of my 1974 MGB 

You tube just recommended this video so I suppose it's kind of too late to say anything but... Old school auto instrument repair guy here so I'll go point by point. Speedo, I'm glad you didn't take it apart because you need to know what you're doing. Firstly, the speedo needs lube, the proper way is to take it apart and clean and oil the main shaft and also the pawl drive cross gear that drives the odometer. But without taking the whole mechanism apart it can be lubed with a syringe and a fine needle. The lube point will be between the main frame and the main shaft worm drive gear, while the mechanism is turning so the oil works its way down the shaft. The pawl cross gear isn't hard to remove, so you should oil that too. Then just a tinch of grease on the gears. The black ring around the rim under glass is called a retainer and its there as a mask/light guide for the back lighting to light up the top of the dial and to hold the lens on. That nasty back stuff under the besel is actually the old rubber gasket turned to black goo. If you ever need to do it again drop the whole bezel into some paint thinners overnight to dissolve the black goo. The speedo needs far more work to it than you've done but still, I'm glad you didn't attempt to take it apart. Fuel, I was cringing when you applied 12 volts to the gauge, EGAD !! These gauges aren't 12 volts they're 5 volts. They are powered by a bi-metal thermal regulator which you will find either under the dash or attached to the back of the dashboard, it's that little silver metal box with three terminals on it. The regulator is switching 12 volts by a set of points on the thermal regulator which, when working properly, the points stay open 60% and closed 40% giving a pulsating 5 volts. Please, please NEVER connect 12 volts to thermal gauges. You can build a simple and cheap 5 volt regulator, plenty of circuit diagrams on line. In fact, you should chuck that thermal regulator as soon as possible because it WILL burn out the gauge eventually. According to my data sheets, the fuel gauge will be 240 ohms at empty and 19 ohms at full. Also, you should check the integrity of the fuel sender. Pressure/temp gauge. They are both in fact pressure gauges, both using a bourdon tube inside the gauge to drive the pointer with a small sector gear. The pressure gauge in this case is being driven by the pressure of the oil. While the temp gauge is being driven the pressure of the fluid in the capillary tube inside the bulb at the end of the capillary. It's not a thermocouple. Both mechanisms are pretty bullet proof but the fluid in the bulb, in this case ether, (that's why you smelled alcohol) often evaporates through porosity in the soldering holding the capillary in either at the gauge head or at the bulb end. Though I have had temp gauges form vintage cars much older than the MG which still retain the ether and work fine. The gauge itself is repairable but needs to be refilled and now that you've snipped the capillary off, that will be a harder job to do. But still repairable. The tacho... You're lucky you have what is called an "active" circuit board in there, positive-negative-pulse. The older MG's used a loop wire with inductive pick up which are almost impossible to repair. In this case, you're also lucky yours is still working. Yes, the chip is the most delicate component but when they fail it's because the capacitors in the circuit break down and short thus shorting the chip. If you know an electronics guy or have knowledge enough yourself, you will need to replace all those capacitors as soon as possible. If you blow that chip, good luck finding a replacement. Anyway, I'm 2 years too late with this post but maybe another reader might find it helpful. Good luck with your restoration.

Thanks fella for sharing your videos and experience..,brilliant as always.👏

Adhesive remover from the automotive paint supply store will soften that rubber butyl they use to seal glass to bezel. Not an instrument mechanic, sir. I'm a painter. Thanks for this priceless video!

I’ve just started restoring the gauges on my 1975 Puma GTE project and this video was priceless to figure out the process, which gauges work, etc. Thank you!

Another outstanding video and presentation.

Enjoyed this thank you.

Outstanding video and presentation.

I have just cleaned up the bezels of my 55 year old instruments by using your method; one I wouldn't have dared to try. So impressed that I went on to do the quarter lights. Stunning results!! Many thanks.

Great information. Thanks for posting!

Excellent, very useful and well explained, thanks.

Working on my gauges... '73 B... Really happy to see the backside of these (since I'm working from the front of the dash) and that the take your time, gentle approach eventually pays off... Which it does. Three done, two left... Thanks.

You are a tremendous help. Thanks a ton.

Great video...👍

Nice bit of work there on the gauges they look great.

8:30 a tip to remove the residual black glue from the inside of the bezel: you mention in the video that the glue becomes softer under heat. Put the bezel in an ultrasonic cleaner filled with hot water (e.g. at 50 degrees Celsius) and some green dish-wash soap. Run it for about 30 minutes. The glue gets very soft and can easily be removed. The problem I faced was that the glass was not glued to the bezel but to the housing. I am struggling to get the glass loose without braking it.

I own a '72 GT and will be following your channel with much interest. I haven't seen a comment on the rust found on the fuel guage. I suspect it has something to do with condensation forming as the warmed air inside the unit contacts the cold housing in winter? Great video. Thanks for putting yourself out there.

They look great, I forget what they looked like before.

Smiths automotive gauges work on a 10volt supply - amazing you didn't burn out the fuel and temp gauges..!

Good job thanks

On my Triumph with Smiths speedo , the "mastic" is a rubber seal that just perished into a gloop which looked like mastic, Acetone removed it easily

Goodman Ross.. Ya need your old intro back with the engine starting.. Still waiting for too fix the back cable on me bicycle 😂😂👍

Educational video I have a number of gauges I need to test

I had a problem with my tacho on a 1969 mgb would display a much higher reading, replaced all the electrolytic capacitors working great now.

Great video thank you. What oil did you put in the centre of your Speedo?

recommend using brass wool instead. The brass wool is softer than steel and should not scratch the bezel.

I spent quite a while trying to find someone to repair my temperature gauge from my Midget. In the end it turned out cheaper to buy a complete new gauge at around £90 I seem to remember. You may fall lucky on EBay but I think by now most will have given up the ghost. Luckily the one on my 74 BGT is still going strong.

While you've got the dials off it might be worth trying different coloured LEDs to illuminate them, green always look very cool to me. Great work as always.

You CUT THE CAPILLARY TUBE!!! I'm dying. So easy to repair. That just cost you 200, Bub.

You and you fancy removable bezel gauges.. 😂 I've got some VDO 52mm and the bezel is bent round the frame, need to replace/clean some glass and it is a nightmare to even attempt! Very jealous

The test for the temperature gauges Bourdon tube is to place it in boiling water, however first thing is straighten it out carefully, then look for kinks and finally carefully roll it in loops around something like a spray paint can, then hold those in place with tape. So much more convenient to work with. The liquid in the tube is acetone for water temp, ether for oil temp and there are DIY repairs online you could try if the tube is damaged, otherwise there are many repair shops that can fix these. Speedy Cables in London would be a place to try. The fact you can smell some volatile liquid suggests the tube was filled and had you tested correctly the gauge would have worked. Think about it, when you start your car how long does it take for temperature to rise, did you apply heat long enough to raise the temperature of the metal, was it hot enough (ie100c) to burn your hand? If you do cut the tube do so at the sensor end so it can be more easily fixed. With your heavy hand why not smack the REV counter with a sledge hammer to get it working?

Always use #0000, steel wool, on all your chrome parts.

what if you tried using something like Goof-Off, Goo-Gone or a tar remover to soften and dissolve that old rubbery substance sealing the glass to the bezel? And, then instead of using rubbery glue to seal the glass in the bezel, use a large O-ring instead to seal it in?

I just mailed you a citation for exceedingly the speed limit 😅

Maybe try some acetone to losen the glue around the glass

Wet scrunched up tin foil works well on chrome

I'm hoping mine still work. Oil pressure gauge is fine but that's mechanical.

2:21:00 why I can’t do this, mine turn just a little

what about the clock

can you fix this for me? Gauges willys truck 1957

This is quite good too - ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-uxJL4b-jt9U.html, and this one - ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-VPT0028GAuI.html.

Temp gauge....acetone.... alcohol.