Classic car GAUGE RESTORATION - Repairing the gauges of my 1974 MGB
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- čas přidán 5. 08. 2024
- I restore the gauges for my 1974 MGB, which includes cleaning and testing each gauge and polishing the chrome and glass.
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Thanks! - Auta a dopravní prostředky
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.
Wow! What a detailed post! Thank you so much. I will pin it to the top of the comments. Have you ever thought of making a video on this subject yourself? The one gauge I have that isn't working now is the time clock. Any hints on what to look at there? It's as though the motor doesn't have enough power to drive the mechanism in it cause you can see it barely trying to tick at the drive gear.
@@Endfloat Actually I have thought about it. Though usually when I get an instrument to repair I usually just get straight into it and then regret not filming it. It's not the sort of thing that many people seem to be interested in so it wouldn't get a lot of views, though perhaps it would still be worthwhile if only for the sake of helping some one on their project. As for the clock, most importantly it needs cleaning and re-oiling as a minimum. On the Smiths clocks I worked on years ago they have a pin attached to the balance wheel (where the balance spring is attached-damn it's been a while) each time the balance wheel turns back and forth the little pin makes contact with a little sprung contact and delivers a small pulse to an electromagnet which keeps the whole thing running. The problem I found with those is that either or both contacts were either worn or burned out. I had some success in realigning the sprung contact to a point on the pin that wasn't burned or worn. The biggest problem with all car clocks is that they aren't high quality precision timepieces and they have 0 jewels, so once they're worn, they're worn and no amount of cleaning and oiling will get them going. But by all means, try cleaning and re-oiling. Here in Australia I use Shellite as a degreaser and cleaning solution for all my intrument work. Getting clock oil may be difficult so use the lightest oil you can find and use only minuscule amounts. Hobby shops usually have very light oil that may work.
@@Endfloat Actually I forgot to add, regarding the fuel gauge resistances. My data sheet shows 240 ohms empty and 19 ohms full but that doesn't sound right for a 5 volt gauge. I know they are 5 volt gauges but I suspect my data sheet may be wrong. For a 5 volt system, the gauge resistance will be in the realm of 70 to 80 ish ohms at empty and around 10 to 15 ohms at full. Most 5 volt thermals run on 73 E and 10 F.
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!
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.
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!
Thanks fella for sharing your videos and experience..,brilliant as always.👏
You're welcome! And thank you for watching!
Another outstanding video and presentation.
Thanks very much! 👍😁
Excellent, very useful and well explained, thanks.
You're very welcome! Glad I could help!
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.
That's great! I'm glad it worked for you. I had a spare gauge I was able to try the technique on before tearing into the gauges from the car.
Outstanding video and presentation.
Thank you very much!
Great information. Thanks for posting!
You're very welcome!
Enjoyed this thank you.
You are a tremendous help. Thanks a ton.
You're welcome!
Great video...👍
Thank you 👍
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.
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.
Nice bit of work there on the gauges they look great.
Thanks!
Goodman Ross.. Ya need your old intro back with the engine starting.. Still waiting for too fix the back cable on me bicycle 😂😂👍
Oh yeah I forgot about that! Grab me next time you see me and I'll do it for you! 😁👍 And I only use the intro sometimes, depending on the video.
Smiths automotive gauges work on a 10volt supply - amazing you didn't burn out the fuel and temp gauges..!
Hmm! You live and learn! Anyway, I think for the short time I was testing them, they'd survive ok.
They look great, I forget what they looked like before.
The chrome was all pitted and grubby, and the glass was dirty on both sides.
Good job thanks
You're welcome!
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
I kinda wondered if that's what it was. Anyway the sealant I used did the trick in the end.
Educational video I have a number of gauges I need to test
Thanks! I hope it's of some help!
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.
Thanks. There's something about the dimly lit incandescent glow of the gauges in an MG that I like though. I tend to feel that most modern car dashboards are too bright actually, so I think I'll be sticking to the original bulbs. They sort of remind me of the glow of the tubes inside an old valve radio.
@@Endfloat the other thing I was going to suggest was ditching the clock and fitting something more useful perhaps a voltmeter ?
If the clock doesn't work, I might consider that.
@@Endfloat I put green LED's into my Triumph Stag dials...makes all the difference. It's not overly bright, the the green colour is a lot stronger and makes the dials so much easier to read, without changing the character and feel of the original dials in my opinion. If I could attached a picture here, I would show you!
@@Rassilon72 +1 for the green dials in the Stag, I did the same with mine.
recommend using brass wool instead. The brass wool is softer than steel and should not scratch the bezel.
Great video thank you. What oil did you put in the centre of your Speedo?
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.
Yeah I didn't have any intention of trying to have mine fixed. They're not rare enough to warrant that sort of hassle, and there's enough to be doing on the rest of the car. I'll find a serviceable one at some stage.
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 job! If mine hadn't worked, that would have been the first thing I'd have done myself actually.
You CUT THE CAPILLARY TUBE!!! I'm dying. So easy to repair. That just cost you 200, Bub.
It was split further down the line anyway.
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?
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?
Lots of useful information there. Thank you. And thank you especially for the insult at the end. It's my car at the end of the day. I chose to share my experiences. We can't all be professionals. And the gauge was well hot enough and didn't work, nor did it work in the car. If you feel the need to insult me again, I suggest you go and watch someone else's videos.
Endfloat honestly the point is not to insult but make a point that if you don’t know how something works before you try to repair it that is your first problem. People watch these DIY videos and take them as expert opinion and could end up with an expensive fix. Yes it’s your car this time but how many naive viewers will follow along also cutting off the tube. You are lucky that it’s a common gauge and probably not expensive to replace not so much with other vehicles, besides you’ve lost the chance for a very educating episode on actually repairing the tube and refilling the liquid and sealing the system.
@@harpersisland Talking of education, Rev isn't spelt with 3 capital letters.
Keith Adams that is absurd, maybe you should Google revolution abbreviation
@@harpersisland Maybe you should google how to abbreviate, you don't spell the abbreviated word with all capital letters. Again. you don't seem to be in a position to pontificate about education.
I just mailed you a citation for exceedingly the speed limit 😅
Oh no! Anyway... 😉
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
It can be done. Just take your time and put some tape over the visible part of the bezel to prevent damage. Pry it back gently and do it bit by bit working your way around several times to get it fully bent back.
Always use #0000, steel wool, on all your chrome parts.
Maybe try some acetone to losen the glue around the glass
2:21:00 why I can’t do this, mine turn just a little
Wet scrunched up tin foil works well on chrome
Yeah I've heard that too.
I'm hoping mine still work. Oil pressure gauge is fine but that's mechanical.
what about the clock
I didn't get the chance to go and pick it up. If it makes for interesting viewing, I'll make a separate video about it. Otherwise, if it works, I'll just be cleaning it up.
can you fix this for me?
Gauges willys truck 1957
It's not a service I provide for others. Sorry.
This is quite good too - czcams.com/video/uxJL4b-jt9U/video.html, and this one - czcams.com/video/VPT0028GAuI/video.html.
Temp gauge....acetone.... alcohol.
Yes, I made a mistake there for sure. Never mind, I'll get another one.