Speedo mechanism

[Tinkley]

I seem to have a small problem with the speedo on the Auto. The complete cable run (both) is new and carefully fitted and lubed. No problem for about 150 miles then jumping - like flicking 70 130 mph etc much more than just a strand beginning to go... Now the base level is about 15mph static and in second I'm doing an indicated 40-50 yeah, and an Auto 1.6 tops over 150mph... so watch out - rice puddings rather than 16valvers, but I can say it has gone off the speedo literally... . One thing is the car was run for well over a year with a non working speedo and this could have allowed something to happen to the mechanism? spiders nests? or that kind of thing.
If this is a mechanical link it will have jumped a worm gear? Anyone reset one? This is not a mileage drum related issue more the basic mechanism. If it is a magnet rotation maybe I can clean any rubbish out. The only thing I could find in the library is stuff about a very fine air gap but no real description of how it works, or how it should be reset.
Having had cables go a bit 'wild' on several bikes and a couple of BXs' (en route to destruction) never seen this wild a fluctuation and yet it will settle solidly for ages and then suddenly play up. However as it now reads about 60-70 when I'm actually doing about 30 I'd quite like to sort it - or just disconnect it..

[Jaba]

I would try first of all spraying the interior mechanism with electrical cleaner to try and combat the stiction or whatever it is.

[Tinkley]

Thanks Jaba. The base level of the speedo is now over 80!... but the odometer works perfectly. Obviously the disc and magnet may need cleaning, the hairspring (could be broken) will need checking at minimum, and hopefully clean and lube? the bearing ends of the shaft jewel?. It may be there is corrosion on the aluminium plate, hard to say without seeing it. Then the fun bit if it seems OK trying to recalibrate it.... Fairly sure this unit is a Jaeger one so I'll try and find what info I can on the beast. I do have a very, very local clock repair guy who may be able to help.

[Defender110]

Not sure what model your car is but found this?

http://www.ebay.co.uk/itm/CITROEN-BX-1- ... SwvUlWqk81

[Tinkley]

Thanks Defender. I'm pretty sure its the 'pod' end that is the problem. The mileage is ticking up correctly just the needle mechanism gone a bit AWOL... I'll whip it off and see if anything can be done. Maybe put on 30k standing still if I swap it with another unit!
I note you can find repairers for older Jaeger Citroens and newer ones ie C5 C4 etc but not so much the 80's 90's vehicles. At least that's just googling, however there may well be some off web specialists around, got enough classic car stuff round here, if you go hunting.

I've also noted that the unit misbehaved with the previous owner intermittently, through some posts on this Forum. Personally I've done cables before just not had the mechanism go wrong. The principle is simple enough, it is just v delicate so I will be careful.

[Defender110]

I have a complete instrument pod off my old tgdturbo if you want it?

[Tinkley]

I'm very pleased to report that I now have a working speedo again!!!

Thanks for the offer Defender, hopefully I've cured it. The problem seems to have been the new cable which I very lightly wiped a tiny bit of lithium/moly (black) grease on pushed a gob of previously applied grease into the spinning disc and magnet. Maybe this new cable is a tiny bit longer than the non genuine broken thing that was in there before (with too long an attachment clip btw) and some monkey put some white lithium in there. They'd certainly been there before as one end of the white part of the instrument holder was broken off with the plastic missing. Either way on carefully dismantling the panel and extracting the instrument pod and speedo things became evident. There was the magnet covered in white/gold grease keeping contact with the spinning disc. To clean up the mess I used an artist paintbrush and acetone with the speedo held at an angle close to upside down to avoid acetone getting on the clear instrument plastic. After some considerable time and cleaning the brush many times and blowing with air the cup and magnet appeared clean.

Next bit of fun was how to reset the hair spring. The default stop position had become 80-85mph so I wound the speedo needle anticlockwise to force the hairspring gently round. By gently forcing it to a three o'clock position on the needle, this then allowed the default (unwound position) to be just above 0 mph so I left it there. After reassembling I took it for a test run through a few 30 mph warning sensor signs - the ones that flash reminding you that it is a 30 limit. At an indicated 30 it did not set them off. It does feel to be reading a bit under say 2-3mph compared to before but quite close. I'll try and calibrate it against the C4 soon, not that you can move it round the other way easily....

This may be helpful to anyone else who gets a wildly jumping speedo when you know it's not the cable. As long as the hairspring is OK you should be able to clean the working part of the magnet and cup, and maybe reset the hair spring.

[Way2go]

I took it for a test run through a few 30 mph warning sensor signs - the ones that flash reminding you that it is a 30 limit. At an indicated 30 it did not set them off. It does feel to be reading a bit under say 2-3mph compared to before but quite close. I'll try and calibrate it against the C4 soon

Much easier to check/calibrate it for accuracy against a SatNav surely? If you don't have one, borrow a friends for a quick run out.

[KevR]

They usually over-read slightly anyway (and always have). And different tyres will also have an effect. So long as it's not setting off 30 alarms when you're reading 25, that's ok.

[Tinkley]

She's got new Pirellis' on the front, and seems to be pretty similar speed feel to the other car with new Michelins', which seem a tad more compliant at least in this cool weather. Went through a couple more of those warning things and I seemed to be the same as other traffic at 30 so it can't be far out. On the test run last night there was no traffic really but this afternoon, I had to go to the optician (no not to read the speedo... ) and it was a lot busier, so gave a comparison to other vehicles.
Can't tell by the gears as the manual has 5 and the auto 4.... and apart from top they are a bit different. Much easier to get economy with the manual btw. It did seem a bit over optimistic before compared to the manual, now the feel of speed is much more similar, though I need to get the auto lowered as she is riding a tiny bit high.

Could always try the old standby, the timed mile at 60....

[KevR]

Drove all the way to East Germany once with no speedo, in my first BX. Used the long motorway miles to work out a series of gear/rev combinations for the various speed limits. My wife had to drive the whole way back due to me having knackered my left leg in a big crash at the Sachsenring (Support race for the MotoGP). I sat feeding her Haribo until she got dangerously erratic and we discovered just how many Haribo is too many Haribo!

[Tinkley]

Nice one KevR. I'm looking forward to this years MotoGP especially after last year - fantastic stuff. Maybe some more head butting of seagulls eh?, but some fantastic riding throughout.

I take it you recovered - eventually? and hopefully no serious injury. I still get occassional pains from a broken wrist many many years ago, when some idiot knocked me off my brothers CZ of all things, but fortunately no arthritis yet....

Naughty Haribo - not declaring the ABV.....

[KevR]

Yes, recovered ok - hadn't actually broken my leg just bashed it about, although I had aggravated an injury to one knuckle, originally caused the night before when pratting about in a mountain bike on the way to the paddock from the bar.... Got plenty of other old injuries to keep me groaning and staggering, unfortunately!

MotoGp should be interesting, especially with the switch to Michelin. Although I bet there are some worried faces around the paddock after Loris Baz's big crash yesterday when a soft tyre split at 290kph on the main straight...