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MG MGB Technical - Tach restore

In anticipation of getting my tach to function, I am tidying up a few bits.
I want it to be visible at night so I am repainting all the white reflective surfaces inside it gloss white. Looking at the inside (see pic 1) you see only the bottom 3/4 is white, the top quadrant is light blue. Anyone know why? I was going to paint it all white.

The other thing I did was at the termination of the pickup coil windings to the board, the wires are extremely fine and there is a short length of unprotected wire which looked vulnerable to vibration. I reinforced this section with a dob of ABS cement which bridges from the board to the wire covering.

Also, I am missing the bottom lamp assembly which is the ignition warning lamp (and jewel missing). I wired up this function to hang on an insulated flange below the dash and would like to get it right. Does anyone have these parts, or know a source?

Art



Art Pearse

Art, I can't answer why there's a blue area but they're all like that.

Bob
R.A Davis

Just a guess, possibly it's to compensate for having only one bulb off-centre on a larger dial by having different reflective colours.

If there's rust over (or instead of) the paint it explains why some dials are so dimly lit as the bulb might be bright but it's light isn't being reflected, same for the car's exterior lights (plus dirty inside surface of lenses or on bulb).

I have an old speedo face in front of me now. The jewel has a tube part behind the front lens bit which is held very securely to the hole through the dial face by some sort of retaining washer (I forget the name of it). These are usually hidden by IIRC a white sealant ?to the tube that goes to the bulb? (I took it apart 13 years ago so forget). I've just take the retainer washer off using a very small flat blade screwdriver and long nose pliers and jewel out (unfortunately it's blue).

I suggest the easiest thing to do is get a non-working speedo and cannibalise it replacing the whole face complete with jewel and it's fixings. I can assure you that the thin wire needle rest stop is very robust.

I've also just taken apart a dual gauge (0-100 lbs/sq" / C-N-H) and in that the inside of the case is all white, not very well coated, the dial was made in week 37 of 2007.

Out of interest I tried the needle mechs to see how far they'd go from rest, the oil goes well passed the H and water to about 80 lbs. (Photos are of a former dial not the 2007 one).






Nigel Atkins

ETA: Forgot you'd want a non-working tach face not speedo face.
Nigel Atkins

It's pale blue so that with the 'yellow' light of an incandescent bulb you get a whiter light to he viewer.

I fitted bright-white LEDS to my instruments and the result is a noticeable blue tinge, which I wouldn't have done by choice. 'Warm white' LEDs give a whiter result.
paulh4

The blue paint and whiter light, in this case, is only to the top quarter which to fit my theory would have to be on the opposite side to the bulb.

On my speedo there are two holes that could be used for the bulb, neither gave light to the full gauge.

With the dual gauge I took apart last night the face is set back on a holder, like a recessed lid for a tin the side is clear (plastic? to allow the light to the face but has four strips that aren't clear (at 2, 5, 7 an 11 o'clock). Why it's has theses strips is beyond me. The bulb is at about 1-2 o'clock, with the case is all, sparingly sprayed, white, so the bulb lines up with one of the strips which must cause some shadow. The bulb position would give most light to the top end of the oil pressure and water temperature. The bulb holder tube is also, sparingly, sprayed white.

I suppose as with much of British manufacture it was though the dials light up and we get many more complaints about our other stuff so why bother trying to improve things, or match the higher quality from other foreign manufacturers.

The dual gauge is reasonable to see at night when lit up but the speedo has dark areas, as do the fuel and tacho IIRC as I've stopped noticing.
Nigel Atkins

The second holes for bulbs in the tach and speedo are for the ignition warning and main beam warning, on CB MGBs at least. They have a tube leading to the 'jewel' on the dial so no light escapes.

The fuel gauge gave the least improvement with LEDs, even though the 'bulb' projects into the case in that but is recessed into the tube on the dual gauges. The fuel light has to bounce around inside the case (white) before it gets out through a hole in the dial at the top to shine on the back of the top part (blue) before it can reach the needle and markings.



paulh4

On my speedo there are two holes plus the plastic insert tube for the high beam warning light, the extra hole I think comes with a blanking grommet. Both of the holes can take the gauge light fitting.

The brass(?) inserted tube for the bulb on my fuel gauge, bought new about 13 years ago, is quite long so sets the bulb back quite a way. I'm not sure if my newer gauge has the sophistication of the blue painted area or is like 2007 dual gauge and all, sparingly painted, white.

I've got older LED white, dome lights in all my dials and have toyed with the idea of replacing them with more modern brighter warm-white LEDS.

So what's the white stuff around the tube end of the jewel lens?

Nigel Atkins

I am wrong -
please disregard the two photos I put up of the dual gauge and how far the needles might go out of marked ranges.

I made a mistake -
with how far the needles might go out of marked ranges as I tried them out of the case and not before I took the gauge apart as I should have which means I haven't allowed for any if there's any possible calibration/restriction of needle movement. I only realised this when I put it back together and could get a variance with the oil only going to 100 or on the 'H' (but the temp I could still getup to 80lbs). I know Mike with the V8 has put his temp needle goes into the oil pressure markings.
Nigel Atkins

So you are saying yours have three bulb holes then not two? What car? My MGB CB has the two I mentioned, V8/RB just one for the illumination bulb. Not thinking of the trip reset cable hole on the latter?

My V8 oil pressure went well into the temp range when the steam pipe blocked.







paulh4

I suppose this is as good a thread as any to post this. The other day a couple of us (me in my MGA MkII and Dave in his midget) took an impromptu drive through the back roads of Tryon, up through Saluda, back down through the water shed, along a new (to me) route over to Hwy. 11 and back via Glassy Mountain and Tugaloo Roads. We had just settled down for a refreshing cold one in front of a cozy hard working A/C unit when my driveway alarm beeped. Not expecting any company I peeked out the door to find a pretty fancy big Ford F-something parked in the drive and a complete stranger extricating himself from its cab. Now Ive only lived up here for 45+ years so Ill admit that I dont know all of my neighbors. Turns out that the visitor was Reid Something (about half the roads up here are named Reid Something) who lives on the other side of Hwy. 14 and raises beef cattle on many acres of old family land.

That was no real surprise since most of the natives are either Reids, Smiths or Campbells. What was a bit of a surprise was that back in about 1969 Reid had started on a restoration of an mga twin cam Coupe. Sadly, I suppose, after spending only about four months on the project his friends and neighbors sent him a post card inviting him to enjoy the lovely scenery available in Viet Nam. The restoration was put on hold and, eventually, the abandoned project was sold to who knows whom.

It turns out, however, that when the new owner took possession he (could have been a she but Im old school and use the masculine third person pronouns generically) left behind one rather nice item: a pristine Jaeger tachometer. Old Reid held on to this priceless artifact for fifty years until today as he passed by my place and spotted a couple of British classics. Home he went to the barn where he dug the treasure out and the rest is history. He pulled in, introduced himself, appropriately oohed and aahed over the MGA and my TD and donated the tachometer to the cause. Im now its guardian and it is looking for a good home. It would prefer to go into a nice car rather than back into a dark and cluttered cabinet of spare parts waiting to leap back into action. If you would, or know anybody who would, like to adopt a good MGA tachometer and give it a nice home, just let me know. You just never know.



J K Chapin

Paul,
really? after all this time, what car you ask.

Click on my 'View vehicle profile'.
Nigel Atkins

This thread was discussed between 27/04/2021 and 29/04/2021

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