Basically I have replaced the instrument cluster in my 2001 pre-plexed 2.0 HDI with secondhand one from a 1999 diesel - my speedo had completely failed (courtesy light test confirmed it was the speedo itself and not the sensor).
Anyway, the new cluster's rev counter doesn't work (not so bothered about that) but I think someone's fiddled with the speedo calibration itself to try and attempt to get it to show the true speed. My old speedo measured about 4mph under the true speed (measured using my sat-nav) whereas this new one measures 3/4mph over. At the moment we're having to remember to read the speedo about a segment under in order to know that we're safely within speed limits, and that's a bit of a pain .
How easy is it to re-calibrate this new cluster's speedo so that it measures like my old one? Is it as easy as just marking where the needle is at rest, removing the needle and re-fitting it so that it sits a bit lower than before?
#2: Re: Incorrect speedo - how to calibrate? Author: Danny., Location: PeterboroughPosted: Mon Apr 16, 2012 5:28 am ---- Take the plastic front off and make sure the needle is touching the little pin.
#3: Re: Incorrect speedo - how to calibrate? Author: c128, Location: EnglandPosted: Mon Apr 16, 2012 6:41 am ----
Danny. wrote:
Take the plastic front off and make sure the needle is touching the little pin.
You have a pin on your speedo? On both the old and new clusters I have the only dials with pins are the fuel gauge and the engine temp - rev counter and speedo both have needles that hang free when at rest...
#4: Re: Incorrect speedo - how to calibrate? Author: gazza82, Location: South BucksPosted: Mon Apr 16, 2012 6:51 am ---- As the speedo is electronic, could it be the gearbox senders are different on the two diesel boxes. So the speedo is OK but getting the wrong signal?
#5: Re: Incorrect speedo - how to calibrate? Author: Harry, Location: StaffordPosted: Mon Apr 16, 2012 7:34 am ---- Does it work correctly as a speedo, just out a little bit? I guarentee it's just needs re setting. The motor doesn't understand where the needle is, as in the needle can be anywhere and the motor will always move the same amount depending on the speed. The needle just needs putting back at the correct position.
Needle is pressured over the motor shaft but could have been put back incorrectly if messed around with. It doesn't haven't splines so is very easy to get it out.
You need to take the speedo apart until you can get to the needles then simply pull it off with a fork if you must then try as best as you can to position it it's around 3 /4 mph less.
Then just push it back on. Best to plug it in and take it for a drive to see, when you happy re assemble the whole unit.
#6: Re: Incorrect speedo - how to calibrate? Author: c128, Location: EnglandPosted: Mon Apr 16, 2012 7:50 am ---- Ah - thanks very much Harry. Yes, it does work fine as a speedo - it's consistently "out" by the same amount no matter what speed.
Will have a go at a little re-adjustment then!
Thanks.
#7: Re: Incorrect speedo - how to calibrate? Author: Harry, Location: StaffordPosted: Mon Apr 16, 2012 8:24 am ---- When you do it once you will get the hang out of it, may take some adjustment though. Last edited by Harry on Mon Apr 16, 2012 9:45 am; edited 3 times in total
#8: Re: Incorrect speedo - how to calibrate? Author: E5GDM, Location: EssexPosted: Mon Apr 16, 2012 9:35 am ---- I thought most speedos over read?
Better that than under read like your old car anyway.
#9: Re: Incorrect speedo - how to calibrate? Author: Big_Rich180, Posted: Mon Apr 16, 2012 9:36 am ----
E5GDM wrote:
I thought most speedos over read?Better that than under read like your old car anyway.
Pretty sure most if not all speedo's over read.
#10: Re: Incorrect speedo - how to calibrate? Author: Harry, Location: StaffordPosted: Mon Apr 16, 2012 9:43 am ---- Yes all speedos are a few mph over the actual speed, sorry if I said it wrong.
#11: Re: Incorrect speedo - how to calibrate? Author: E5GDM, Location: EssexPosted: Mon Apr 16, 2012 9:56 am ----
Harry wrote:
Btw they are suppose to be a few mph under the actual speed so you may want to set back a little more
These posts read like we're talking about indicated speed? In that case it should read a few mph over the actual speed your cars really doing. Other wise if it was a few mph under the actual speed you'd be going faster than indicated & that would be dangerous at the least.
I.e speedo says 30 but if reading under car would be really be doing 34,
Or speedo says 34 but if reading over car would be really doing 30.
I know what one I'd rather have.
I think we might be all be getting a bit confused with our over & unders, but the speedo needs to be showing more speed on the clock than the vehicle is actually doing.
#12: Re: Incorrect speedo - how to calibrate? Author: E5GDM, Location: EssexPosted: Mon Apr 16, 2012 9:58 am ---- Sorry Harry, I'm so slow posting youd corrected yourself before I got my last post up. I left it there anyway. Hope you don't mind as I thought it might answer the OP's question.
#13: Re: Incorrect speedo - how to calibrate? Author: kit325, Location: LondonPosted: Mon Apr 16, 2012 12:47 pm ---- Where's your needle poiting when your car is stationary?
If is pointing zero when your stationary then your fine. Is not the cluster need adjustment.
Otherwise u need to take out the needle carefully carefully with a folk. Still plug in your speedo without the needle, once u start up the car, re-insert the needle into the postion poiting zero (half insert). Then drive your car to 30mph then come to a stop, it should drop back to zero. If it working,fully insert the needle and reinstall all the component.
I hope u still keep your old speedo, cause the cluster is repairable. The main reason for preplex cluster motor failed mainly because of the small plastic pin ion the casing that holding the small gear failed. U can replace your rev cluster motor as well cause they r the same.
I repair mine by soldering in a metal pin into the plastic casing to replace the previous fragile plastic pin and it working fine now.
#14: Re: Incorrect speedo - how to calibrate? Author: c128, Location: EnglandPosted: Mon Apr 16, 2012 1:46 pm ----
kit325 wrote:
I hope u still keep your old speedo, cause the cluster is repairable. The main reason for preplex cluster motor failed mainly because of the small plastic pin ion the casing that holding the small gear failed. U can replace your rev cluster motor as well cause they r the same.
I repair mine by soldering in a metal pin into the plastic casing to replace the previous fragile plastic pin and it working fine now.
Ah, very useful, thanks for that. Yeah, I've still got the old cluster, and I will have a look at the failed motor.
What I hadn't realised in all of this is that the rev counter and the speedo have the same model of stepper motor. So, what I should have done originally was just swap the rev counter/speedo motors round in my old cluster before buying a new (secondhand) cluster. I've done that now anyway and I'll put the old cluster back in with motors switched - if the speedo works fine like that (with/without a bit of calibration) then I'll swap the speedo motor from the new cluster back into the old one as the rev counter motor and I'll be back in business (and with the correct mileage again ).
#15: Re: Incorrect speedo - how to calibrate? Author: c128, Location: EnglandPosted: Mon Apr 16, 2012 1:54 pm ----
E5GDM wrote:
I thought most speedos over read?
Better that than under read like your old car anyway.
Don't think I was very clear at all in my original post, so apologies for the confusion.
The problem is that the new speedo reads, say, 30mph when I am actually doing 33/34mph. The old speedo read 30 when I was actually doing 26/27mph. I'd expect the latter.
I think my plan, now that I know the rev counter and speedo share the same type of stepper motor, is to make a fully working cluster out of the two based on my original cluster (for correct mileage). Then use the advice here to calibrate the speedo.
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