Speedo not working, is now but it's out

[craigieeb]

Guys, just been out for a cheeky little drive, and noticed straight away the speedo is not working,
it all lights up, the rev counter works, but i have no idea what speed i am doing,

things i have tried

hitting the dash.

they are 325 clocks, but i have an M50 conversion and im also running Vems


any ideas?

[kam-325i]

Diff sensor plug ????

[craigieeb]

I thought that, but during the conversion, I chopped out a length of the wire and put some fresh wire on there, because it looked a bit "ropey"

but i'll have another look at that tomorrow

[Jesus325iTouring]

You must have been driving too slowly

[craigieeb]

I dunno like,
the brown stains tell a different story

[Jesus325iTouring]

Ah,all of those horse's were let out the stables then

[craigieeb]

There was no stopping them Rog, I just had to hold on and enjoy the ride



I'v checked the wiring and the plug on the diff, all seems fine and in order....

any other suggestions?

[Silverfang]

ACtual sensor in the diff might have failed, do a continuity test on the wiring though?

[magpie]

i've got a diff sensor here craig you can have but it's from an open small case so might be DIFFerent <<

[craigieeb]

Boom Boom lol

I think there all the same,
i'v got a spare one kicking about somewhere, i'll see if i can hunt it out and swap them over,

[jmc330i]

Does the trip meter etc still turn even when the speedo isn't moving?
This happens on mine, Brianmoooore made some suggestions about the possible problems on the clocks on a thread I started although I've not got round to actually looking into it yet.

[craigieeb]

Hmmm, i'v never noticed that tbh,

what were the suggestions Brian made?

[jmc330i]

what were the suggestions Brian made?

Have a look at the solder joints on the speedo circuit board that secure the pins that plug into the cluster main circuit board.
Undo the screws on the back of the cluster case that are directly behind the speedo, plus all the ones that hold the front and back halves of the whole cluster together, pull the two halves apart, then just pull out the speedo.

Tbh, I never got round to opening the cluster up, I just swapped the whole cluster with another I had and problem solved.

[gromgsxr]

My speedo would flicker about and be al over the shot, then it jut gve up one day, I tried dif plug wiring ect with no joy, pulled clocks apart and some of the soldered joints looked a bit ropey, so got the solder iron out and re flowed it with fresh solder been a good as gold ever since. I'd always try the sensor and that first though.

[craigieeb]

I'll just drag this one up again....



I changed the sensor on the diff and hey presto, job jobbed

But.........



its reading over, quite a lot actually, it starts at being 10 mph over and increases with speed,

(tested against gps)

is there anyway of re-calibrating these

[Grrrmachine]

Where did you get the replacement sensor? There's a chance that, if it came off a different size diff, that it'll be counting an incorrect number of pulses per revolution.

No calibration as far as I'm aware.

[daimlerman]

Where did you get the replacement sensor? There's a chance that, if it came off a different size diff, that it'll be counting an incorrect number of pulses per revolution.

No calibration as far as I'm aware.

Diff sensor counts the revolutions of a half shaft,so diff ratio will not matter.

Tyre size will affect speedo reading,though.

[TPS]

I always thought those Diff. Sensors were the same part no., across the range.

[Grrrmachine]

Where did you get the replacement sensor? There's a chance that, if it came off a different size diff, that it'll be counting an incorrect number of pulses per revolution.

No calibration as far as I'm aware.

Diff sensor counts the revolutions of a half shaft,so diff ratio will not matter.

I knew it was counting a petal wheel, but didn't know what that was attached to. Good to know that's not an issue.

No idea what else could such an inaccuracy other than dodgy sized wheels then.

[craigieeb]

The sensor I put in, was off an old medium case 3:64,
and the diff I have on now is a medium 2:65

the tyres are a 50 profile x 16"
I dont think the tyres I have on now could be the cause to throw the speedo out as much as it is....

could they?

[daimlerman]

Speedo will always be approximate but should read high.

I'm no expert on tyre sizing,but a 50 profile seems high on a 16'' wheel,'dezzy' is the zone tyre expert and will be more able to advise.

[Rav335uk]

if the tyres are 205/50/16 then the rolling radius is right.
225/45/16 is the next size up to keep the rolling radius the same.

[Grrrmachine]

50 profile of what width? Profile is a percentage.

Then again, even if you've got 215's on there you'd only be 5% out.

[Rav335uk]

Try this site Craig to work out your rolling radius.

www.willtheyfit.com

[craigieeb]

50 profile of what width? Profile is a percentage.

Then again, even if you've got 215's on there you'd only be 5% out.

the tyres are a 195 50 16 (yokohama A048's)

Try this site Craig to work out your rolling radius.

www.willtheyfit.com

Rav, what am i doing on that site mate? lol

[Rav335uk]

Done it for you

http://www.willtheyfit.com/index.php?wi ... mit=Submit

according to the site, the speedo error is 0.8% out.

[craigieeb]

So going by that (cheers Rav) there is defiantly something else messing up the reading,

at 60, its reading 70, then it just goes up and up,
when it was on a private road, it started reading 20 mph + over the top

so an indicated 150 on the speedo was only seeing just shy of 130 on GPS

[Rav335uk]

You got the right coding plug for the clocks?

[craigieeb]

Yeah, course, it started life as a 6 pot, and it still is now

[Rav335uk]

What engine management you running??
WOuld that be a factor ?

[Grrrmachine]

I've been digging around for my own speedo issues and found out:

Motometer dash clusters have a potentiometer that allows you to calibrate the speed signal. Pictured here:

http://www.e30tech.com/forum/attachment ... =123682733

For more info:

http://www.e30tech.com/forum/archive/in ... 73541.html

[craigieeb]

I'v got the speedo out, and mine doesnt have anything to adjust

[Grrrmachine]

Shame - that's a VDO unit then.

You could try buying another speedo that DOES have the potentiometer on it; they're interchangeable on the cluster.