So, our family picked up a 2003 S40 locally fairly recently. It was a salvage vehicle from hail damage in 2006, was repaired and has been used as a locally driven work car in my rather non densely populated city. Its mainly been sitting there as the kiddo isnt yet able to drive without an 18 yrd old with him yet. We did get the car a few months ahead of time, so its just been sitting there, rarely being driven. Anyways , its developed a problem that some googling doesnt seen to have helped with at all. The speedometer is reading about 9 mph low. The car was travelling at 30 mph as indicated by the speed limit sign equipped with a radar gun actual speed indicator and was reading just a hair over 20 on the speedo. When we bought it, i made it a point to drive by one of such signs to verify the speedo was accurate, and i recall it being accurate. The only thing i see online is replacing the speedometer control unit, and that sounds like a bundle of joy. Any thoughts on what could cause a newly formed incorrect speedo reading?

 

does the needle return to zero and start 9 mph off or is it proportional to the road speed? I assume the tires are close to the correct size (even so, that would only contribute a 2-3 mph ). I'd think its possible the needle could be off if its consistently wrong by the same mph's or the control unit is bad. Does the odometer seem correct - ie what Google Maps or Waze says for a given route of say 10 miles?

 

all very good questions and great toubleshooting ideas. i will take it for a drive myself this evening and find out. The speedo reports ive got are from the 2 kiddos and my fiancee. They all drove the car past the same speed limit sign with the radar gun in it on separate occasions and have all reported it being off. Ill do a distance/time check on the highway vs gps info and then drive by that speed limit sign myself several times to get the different readings. Thank you for the reply!

 

I wouldn't try the radar sign in front of your local schools :-) I would take the car out on the freeway, set the cruise control at 60 on level ground and see what Waze reports. its actually pretty accurate. Even better if if you can find a measured mile on the freeway and time a mile at 60 mph. should be 60 seconds...but most cars show 1-2 mph faster than actual.

 

right on, ill do that too. the radar sign i commonly see is on a street that doesnt have a school, nor a school zone. Not exactly sure why the radar sign is there tbh. Its a 30 mph zone and i cant remember a time that i wasnt passed by a car going at least 10 mph more than me when i was doing 35 according to the radar and the speedo in my Altima, which im sure is fairly accurate. Ill give waze and the mile markers a try to see what the needle does at highway speeds too

 

ok, so i installed waze and went to drive the car. I made it a few miles before i came to a stop where i noticed that the speedo needle sits a fair amount below zero when the car is stationary. I got on a 40 mph zone and cross referenced waze with the speedo, and waze showed 40 on the nose and the speedo was a hair over 30. Proceeding on to the interstate, still cross referencing waze, the speedo was still what i could best estimate 9 mph lower than what the app showed.

TL : DR
the speedo is showing roughly 9 mph lower at all speeds and reads around -9 when stationary.

Am i about to crack the gauge cluster open and mess with the needle?

 

Short answer. Yep. ;-)

It does sound for all the world like your speedo needle is just offset 10mph to the left. Wish I could tell you how to fix that...

 

what in the crap would cause it to do that? i cant imagine that its glued on and the glue came loose. Im envisioning it being more like a capital D shaped peg, like the posts for older climate control *****

 

I have to agree that it makes sense that the speedo pointer would be indexed to the shaft somehow. I suppose there may be some sort of adjustment in the mechanism itself that would allow zeroing the pointer, but I didn't find any info in a (quick) 'net search. But the fact that the needle sits below the zero point tells me that's what's happening. No way that should happen unless something broke / bent.

There are quite a few places that advertise the ability to fix instrument clusters. I believe (but am not sure) that you'd need the dealer to reprogram a "new" boneyard cluster (which is a shame, since you can pick one up for chump change on eBay).

 

are you serious??? this seems like such an easy fix for the dealer to need to get involved. Thank you for the term "indexed" as it was obviously eluding me LoL anyways, that sounds really goofy to need to do that. Its not like the old days when you could manually mess with the odometer

 

The dealer involvement is in reprogramming the ECU (I assume) so it'll play nice with the new cluster. The mechanical part is a piece of cake (in that relative sense that tearing your dash apart can be easy). ;-)

Yeah, old school speedos were easier to deal with (and old school odos were easy to "wind back", too!). ;-)

 

so the new cluster is only if im unable to correct the needle issue, correct? i hope that im not interpreting that i would need a new cluster to correct this issue with the goofy needle. sounds like a sledgehammer to push in a thumbtack

 

Maybe. If the speedo "needle unit" is bad, you're either going to have to replace the cluster (ouch) - or maybe if you're really lucky and/or brave (or like me, too dense to know when to stop), you might be able to buy a used cluster and swap out JUST the needle drive unit (I just made up that term). Might even be worth buying one on the cheap just to see how involved removing and replacing it would be.

 

i believe the electric motor used to turn the different needles into the correct position is called a "stepper motor". Totally not trying to split hairs or be pedantic. Im the same way, never know when to stop LoL If its consistently off by 9 mph even when its supposed to read 0, i should hopefully be able to get it to 0 and go from there. The stepper motor might require some soldering. No biggie there.

Anyone else suggest anything other than cracking the cluster apart and adjusting the needle?

 

Random thought here... I was looking at newer clusters (like the one in my '05 V50), but just saw one out of an '03 S40, and notice that it has a hard stop "peg" that should keep the needle from dropping below the (more or less) 5mph point.

I have to wonder if your speedo has this peg (sounds like it doesn't, if the needle is resting below zero). Maybe it's just a matter of cobbling together a replacement "peg" (I'm thinking "drill and glue") that stops the needle in the right resting position - and maybe the mechanism "calibrates" to the resting position?

 

I've never disassembled the cluster on an S40 but I did do an odometer repair on my 850 which required popping off the needles for the gauges (which is why the process states to mark where the needles are). With that said, seems quite possible somebody opened up the cluster and did a repair and didn't replace the needle quite right or the needle have shifted slightly over time. The 850s are just pressed on so seems reasonable to think the s40 is the same. If you decide to open up the cluster, what I'd do is secure the pin before popping off the needle, then reinstall the needle enough to move the indication the missing 10 mph. I suppose you could apply some glue (epoxy or other to lock the pin in place better if it seems loose. Good news is the gauges come out pretty easily - there are vids on Youtube (search for a topic like how to replace dashboard bulbs)

 

this is a very good thought man!! Thank you! The resting post hadnt even crossed my mind, but youre right, there should be one. Im gathering all this info in my mind to formulate a plan and this is the type of fuel for my mind i was hoping for. Much appreciated!

 

good stuff here too! you guys are why i love forums like these! Thank you VERY much!!

i cant find a "like" button for the helpful posts here, am i just missing it?

 

update:

i got the gauge cluster out and moved the needle. It was fine for about 7 miles of driving. Turned the car off and it went back to zero. Went to drive it again, and its back at -9 when at rest. when i had the cluster open, i tried tugging on the needle, and that little fu*ker is stuck on there good. Im afraid ill cause more damage than id fix if i pried it off