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MG MGA - Applications for Jaeger tachometer RN 2312/01

I would really appreciate assistance with identifying details regarding this tachometer I have been given. I am confused regarding its applications/features. Photo of the back attached.

Moss Europe has this as a mechanical tach from the MGB 1962 to September 1964 – replaced by a Smiths electrical model RVI 2401/00 from October ’64. A web retail site claims it to be from an MG midget MK1 948 1961-62, but again a mechanical unit. Part numbers are (Moss) BHA 4212E, retail site BHA 4212. I can find no definitive reference in the archives.

The photo shows an electrical pulse loop and no input for a cable drive, so it would appear to be an electrical tach. I am presuming it to be for a positive earth car. There are no threaded posts for a securing clamp, nor for the securing nut shown on the Moss site for the mechanical version. There is, however, the ring of spring steel shown, something I’ve not seen before, which appears to constitute the securing mechanism for this particular instrument. The earth fitting can be seen as well as a post with screw/clamp fitting, which I presume to be the input power post.

The face is definitely that of a British Jaeger RN 2312/01. Orange zone 5500 to 6000, red from there to 7000. The needle is hovering mid the orange zone with a dampened movement, allowing a slow swing to the edges of the orange. Assuming it can be done, I will adjust that. Only marking on back is the manufacturer and a notice that it contains no jewels.

I’d prefer to know what I’m opening if there is a chance it might be a mechanical converted to electrical – assuming both that it could have been done and would have been worth the trouble to a PO.

I am thinking of fitting the Jaeger to my 69B. The original tach in my car (Smiths RVI 2430/00) no longer operates and the needed replacement board is apparently no longer available for it, at least not down here.

I will post this to the B and Midget boards.

I would appreciate any information on known applications or features of this Jaeger tach.

Regards
Roger



Roger T

It looks like the face has been placed in an electronic instrument. As you said, I think you will find that Jaegar code belongs to a 61 Midget with mechanical drive.

steve
Steve Gyles

I agree with Steve. If RN 2312/01 was used in '62-'63 three bearing MGB, perhaps someone replaced their engine with a later five bearing unit and swapped the tach for a matching electric unit but kept the face from the original mechanical tach.
Andy Bounsall

This would be valuable to someone with an earlier car who has done the swap for the later engine. You didn't post a pic of the face, but I am guessing it matches the MGA gauges?

JIM
AJ Mail

Lets see the face. I may be installing an 18V in a '61 and that would be the ticket!
Russ
Russ Carnes

Thank you gentlemen for the feedback. I'm inclined to agree it is a conversion, an RN 2312/01 face on an electrical unit. Researching further, all references to this # indicate only a mechanical version. Nobody has offered that they have seen it in electrical form.

I am attaching a photo of the face. This appears consistent with a photo in Clausager (p43) for a '64 MGB car - 500K steps with orange from 5500 and red 6000 to 7000. That was mechanical up to September '64.

Can anyone advise if this face is the same as an MGA?

I guess I will know more when I get it opened. I'm hoping the needle position is only a case of it having been put on at that angle at some time.

I may need to convert to negative earth and will recalibrate it if it shows a reaction to 12V input.

Jim, as I mentioned, if it does work I will probably swap my existing tach face to this unit and run it in my B. Of course, that would mean a spare RN 2312/00 tach face sitting on the shelf.

Regards
Roger


Roger T

Roger

The dial is the same as the MGA except for the version number we have discussed. On the instrument the needle should extend out to the edge of the scale and the centre boss is different. The 2 retaining screws are also wider apart than on the MGA instrument.

Steve
Steve Gyles

Roger

This is a typical MGA face.

Steve


Steve Gyles

Thank you Steve. Yes, there are differences. Another I see is the position of the face securing screws. Difficult to see on your photo (RN 2350/01?), but on my RN 2312/01 there is one clearly visible on (and disrupting) the white line at 5500K. The other is directly opposite. So a number of differences.

Opened it this pm. The clock-like copper appearance fine spring appears to be adrift of its solder point on one of the posts - I presume that explains the needle position. Otherwise quite clean and 'fresh' looking. The can is indifferently painted in white with a line of pale blue where others have an angular pattern of that colour.

I'm still bemused by the apparent securing system - the spring steel ring, and no securing nut post or bracket posts.

I think I have a real mongrel!

I appreciate your help.

Regards
Roger
Roger T

Roger, yes I mentioned the screws. You can just make out the right hand one on my photo at the 3-o-clock position of the boss, well inside the amber segment. The screws on these dials are very small and almost indiscernible. Yours would seem to have slightly larger and thicker heads, but that may just be an illusion.

Steve
Steve Gyles

This thread was discussed between 11/06/2012 and 13/06/2012

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