318i Auto Speedo not working

[Hairyarse]

Well after waiting 3 weeks for a new speedo sensor to arrive from BMW (and being £75 lighter) it's not fixed my inop' speedo

When I picked the car up from London, it didn't work, then started bouncing up and down and gradually getting higher, then after about 30 mins the speedo worked perfectly, until about a mile from home it packed up again and hasn't worked since.

Before I start ripping the dash out - which I'd like to avoid! - has anyone got any ideas on where to look next?

Thanks in advance.

Andy

[maggspower]

Replace the wiring to the sensor at the diff end. Cut off the plug and about 18", solder a new piece in.

This length of wire is subject to much vibration, bends, road salt etc, and can break down over the years.

Clocks come out easy by the way, but it doesnt sound like those, if everything else is working on them (SI batt problems).

[Brianmoooore]

You'd be £75 better off if you'd tried the zone first! Sensors rarely fail.
The main cause of E30 speedo. failure is an internal fracture in the lead that goes to the diff. The copper becomes brittle, so the last 300mm of lead, including the plug, needs to be replaced, not repaired. An E30 headlamp plug and length of lead from a scrapper is ideal for the repair.
The other main cause of speedo. failure is cracked solder joints where the pins of the plug in speedo. module are soldered to its circuit board. This can usually be diagnosed by thumping the dash above the speedo. and noting if this affects the fault.

[Hairyarse]

Thanks for the reply (btw think you need to reduce your avatar pic size - it's filled my screen!! LOL)

I forgot to mention that the odometer is not working either it that makes any difference? I'll have a go with the wiring, see if that helps.

Cheers again
Andy

[Hairyarse]

(Avatar comment was at maggspower btw lol)

Thanks Brian. I think I did so much searching on the net before I had it in my head that I'd posted on here - I didn't - oops!!

I'll take a look at the wiring next, sensor can go on ebay I guess!

[Hairyarse]

Ok thanks Will for the info ;)

[Hairyarse]

Just a brief update. I've taken off a section of the end of the cable going to the diff sensor. I had continuity in it, so didn't seem the problem - it wasn't and I've re-attached it.

Not working is the speedo, odometer and fuel economy gauge. I'm pretty certain that when the speedo was working, the odometer was also.

So I'll now take out the instrument cluster and check/replace SI batteries

[Hairyarse]

Ok now I'm really baffled!! I've taken the cluster out and apart, having read the how to and expecting to find a circuit board with two SI batteries on, and I have nothing!



Were earlier models powered a different way?

The front of the circuit board looks generally ok;



There's a couple of areas that may be suspect? Firstly, a darker looking track than the rest;



...and another here, 2nd up from the bottom. In the pic it looks like dark spots but it's actually shiny copper coming through the top film by the looks of things;



If anyone can shed some light on this it would be gratefully appreciated, I'm at a loss what to do now, other than try my luck with second hand clocks or send these off for repair. I'd rather keep the originals given the low mileage of the car.

Thanks in advance.

Andy

[Hairyarse]

Ok, so just found the batteries in the front half of the clocks Must be different type to the how-to I read! lol

[Hairyarse]

No I've sussed that much, a more sensible couple of questions (hopefully! )

Firstly, these batteries don't want to seem to come out. Am I being too delicate, or missing the obvious here?



Secondly, that big orange sticker, does anyone know exactly what they mean by that??

Thanks again ;)

[Hairyarse]

It's amazing what you can work out by surfing the net just that little bit more! LOL

Found and ordered these - http://www.smallbattery.company.org.uk/ ... _VBR-T.htm

So the batteries are soldered to the board. I'll swap these over when they arrive, although not convinced it's going to sort all of my issues. We'll see

[Brianmoooore]

although not convinced it's going to sort all of my issues. We'll see

You are probably right here, I'm afraid. There are two versions of the SI board - one that uses non rechargeable lithium batteries and one that uses NiCd rechargeables.
The problems listed in the wiki are relevant to the NiCd version - these tend to go short circuit when they fail, pulling down the voltage supply to other instruments in the cluster and causing the problems listed.
The batteries on your board are solely to maintain the volatile memory circuit when the main car battery is disconnected, and don't do anything when it isn't.
The big orange sticker is pointing at a jumper link on the board that acts as a switch to connect the batteries, and indicates that your board was fitted as a replacement at some time in the car's life. Lithium boards fitted as original equipment at the factory didn't have the jumper link - they had a small wire link permanently soldered between two spare holes you can find on your board, near the jumper pins.

P.S. In your first pic. you can see a large 220 ohm resistor just beside the blue socket. Check the soldered connections for this resistor, which are near the temp. gauge on the print side of the board. If they've never been attended to, they will have deteriorated, and give rise to a fault with the brake pad warning light.

[Hairyarse]

Many thanks for the info Brian, much appreciated ;)

I spoke to BBA Reman today too - http://www.bba-reman.com/UK/

They can do a diagnostic check for £35 + carriage + VAT which doesn't sound bad, but once they confirm the cluster is faulty and can fix it the total rises to £150 + carriage + VAT. I guess it may come down to the toss-up between a warrantied fix and cheaper second hand clocks that could break any time through age

[Brianmoooore]

Clocks do not "break through age"! There are a few well documented points that need attending to (WillNZ's jellied odometer cogs are unheard of in the UK - it's a hot climate thing), and after that they will last for ever.
Find out why your speedo isn't working before you buy anything - you don't need BBA Reman to do that. The sensor in the diff is a simple reed switch worked by a magnet and notched steel disc.
Check the switch with a meter at the cluster plug. It should read zero/infinity/zero/ infitity/etc. several times for each turn of the rear wheels.

[Hairyarse]

I've replaced the diff switch with a new one, still doesn't work, as well as the length of cable that was in good condition. With the low mileage it really is quite tidy underneath. I may put it all back together on the off chance that I've nudged something and it works again!

[Brianmoooore]

Check the sensor at the white cluster plug, pin 8 (brown) and pin 12 (brown red). Push short lengths of bare wire into the plug to connect the meter probes - don't force the probes into the plug.

[Hairyarse]

Excellent, thanks Brian

[Hairyarse]

Ok I've tried the test I think I've done it right but not sure with the results I got?

I couldn't see where the wires went in to each terminal so tried all four permutations of what could be pins no 8 and 12. Below is the one that get me a result;



With the rear wheels turning and meter on resistance setting, it just constantly read infinity. However, when I put my foot on the brake I got a resistance reading. As soon as the brakes were off and the wheels turning again I got infinity.

With the other three permutations of what could be pins 8 and 12 I just got infinity reading for both spinning and braked rear wheels.

Does that help any??

Cheers
Andy

[Brianmoooore]

Pin numbers for the end of each row are marked on the sides of the black bit, just hidden by the white shell.
Pin 1 is bottom left as you have the plug shown in your pic, so it looks like you have 8 and 12 correctly identified.
There should be absolutely no connection whatsoever between these pins and the brake pedal, including any common earths!!
Try checking for continuity between the pins at the white plug and the plug at the diff. It should just be two wires from the front to the back of the car, going through one plug and socket on the RH side of the rear seat pan.

[Hairyarse]

Thanks Brian, I'll check that ;)

[Hairyarse]

Ok I've checked and I do have continuity from pins 8 and 12 behind the cluster, all the way back to the plug on the diff sensor.

Does that mean then that it is an issue with my clocks?

[Brianmoooore]

You need to look into why the brakes are affecting the readings from the sensor when measured at the cluster plug. Until you see pulses (open circuit/short circuit, etc.) from the diff. sensor, at the cluster plug, as the car rolls along, then the clocks remain innocent until proven guilty.

[Hairyarse]

Fair point, more digging required then. Thank you again ;)

[Hairyarse]

Ok I've run the test again and maybe I just had the wrong scale set on my multi meter (i.e. too low?)

Now when I test it, I measure a resistance across terminals 8 and 12 which varies with speed. When I hit the brakes and the wheels stop turning it measures zero. To me that sounds like it's all ok?

Given that the MPG meter is not working either which is on the other side I'm assuming it's a track on the board that's faulty but as always I'll listen to those much wiser than me on this subject! lol

Cheers
Andy

[Hairyarse]

Has anyone got opinion on this? It looks like clock replace/repair time but second opinions are welcome!

Thanks in advance.

Andy

[Hairyarse]

Is anybody there????

[Hairyarse]

That'll be a no then!