Tacho Showing Over 9000?!

[Kinks]

My tacho one day decided to go crazy, when idling it was sitting around 4000RPM and as soon as I drove off it would bounce around between 7000 and 9000RPM. Tapping the dash behind the steering wheel made the needle fluctuate so it was clear something wasn't right in the instrument cluster. Plugs were all in firmly so the cluster itself was the next suspect. Since I managed to fix it here's what I did:

Start with cluster out (there are plenty of other guides to get to this point):

Around the edge of the cluster you need to unclip the plastic clips (arrows) - there are a bunch of them top and bottom of the cluster, work slowly and gradually unclip them all and the front will pop off. Careful about the reset needle for the trip meter, if you are agro with it you will damage it. Be gentle once you've got the clips undone!!

You should now have a naked instrument cluster (oooh baby!)

Flip it over and undo these 6 screws, careful as when you undo the last one the tacho will fall out.

You should now have a naked tacho module (I'm excited)

Here's a suspect capacitor, looks like it's had better days. It looked suspect, so I changed it. If you change it with the same value you shouldn't have to touch the adjustment pot (right next door). If you do need to recalibrate your tacho this trimpot will let you.

Replace the capacitor with the same value of 15nF (replacement is marked 2A153J - the 153 means 15 with 3 zeros, in picofarads. 15000pF = 15nF). Adjustment potentiometer highlighted in case your tacho is now off - mine wasn't so I didn't have to touch the trimpot (I did anyway, but that's because it was there and I wanted to play with it).

Put it all back in reverse order and your tacho will be less crazy*. I took a photo of 9000RPM for posterity, I hope my RB never actually hits this since it would not end terribly well

(*statement is true if you have made the necessary prior sacrifices to the skyline gods. I take no responsibility for cack-handed, ham-fisted or butter-finger moves. If you end up in the emergency ward with burns from your soldering iron please tell me which ward you are in so I can point and laugh)

[fib]

My tacho did that too. I replaced it

[matticus]

Finally got around to doing this one on the weekend and my tacho is still playign up

my next move will be to resolder all the contacts. Im guessing there is a possibility that a contact is not secured to the PCB anymore.

If i cant find anything ill probably bite the bullet and buy a new cluster.

or maybe a tacho from nissan if there are any left...

[Kinks]

the only other thing you can try is "exercising" the potentiometer next to the greencap. this pot is used for calibrating the tacho and normally will be near enough if you leave it alone. if the contact has gotten dirty then it will make poor contact and possibly cause the problem as well. using a screwdriver turn it back and forth a few times and then reset to the original position.

[matticus]

So I finally fixed my problem. Along with replacing the capacitor I also heated the solder on each component to remelt. This also included taking off the fact and melting the solder on the top 4 prongs that run the electromagnet.

Took the car out for a test drive and it was working well. Bonus is that i know it accurate as i compared it to my SAFC2 readout and was almost spot on (within 50rpm at 5000revs)

When you take the needle off, push it around to the limit (past 9000) and make a note of where it was sitting. When you put it back in put it in around 6000rpm make and then slide it around to the point where you took it out. This is what i did and its still accurate.

Hope everyone finds this useful.

[matticus]

So I finally fixed my problem. Along with replacing the capacitor I also heated the solder on each component to remelt. This also included taking off the fact and melting the solder on the top 4 prongs that run the electromagnet.

Took the car out for a test drive and it was working well. Bonus is that i know it accurate as i compared it to my SAFC2 readout and was almost spot on (within 50rpm at 5000revs)

When you take the needle off, push it around to the limit (past 9000) and make a note of where it was sitting. When you put it back in put it in around 6000rpm make and then slide it around to the point where you took it out. This is what i did and its still accurate.

Hope everyone finds this useful.

Well two days down the track and my tacho has lost it again (not as bad as usual) I think it may have to do with a screw which has been used, it is slightly corroded which would cause bad contact.

[S1LV3RTRACKS]

I had the same issue with my tacho a while back. I tried replacing suspect components much like how this thread suggests with no success. Ended up tracking down another cluster for sale and I simply swapped my old tacho module out and replaced it with the good one from the new cluster. Fixed the problem straight away. A tip for anyone who plans to open their cluster and remove parts - ensure your hands are free from dirt and oil or you will leave marks on the faces of the dials.

[JPCR33]

i did this today to my car as i was having the issue with my taco

put it all bak in and test drove it, and still having the issue

what else could possibly cause the issue

any ideas would be great thanks

[HugeSkylineFan]

i did this today to my car as i was having the issue with my taco

I was having problems with my taco too, might I suggest upgrading to the new and intresting Burito

(This is a Burito)

Thank me later-

[Kinks]

it could be a dodgy spot on the trimpot next to the cap.

mark the position with a permanent marker so you can put it back to where it was and try turning the pot a few times back and forth to "exercise" the contact inside. then set it to a different position (maybe 30 degrees off where it was, more towards the middle of the dial). put it back in the car and test.

if the needle has stopped jumping around then it's just a dirty pot. the RPM value will be way off, go back and adjust the pot again until it is back to where you were and hopefully the contact will have come good.

if not then i'm not too sure - mine has been spot on since i replaced the cap so there may be multiple causes of the problem.

[JPCR33]

thanks mate

ill try that, but i have found a taco for sale so its on its way if all else fails

[Binofski]

the only other thing you can try is "exercising" the potentiometer next to the greencap. this pot is used for calibrating the tacho and normally will be near enough if you leave it alone. if the contact has gotten dirty then it will make poor contact and possibly cause the problem as well. using a screwdriver turn it back and forth a few times and then reset to the original position.

Working for me so far!!!

[Tony de Wonderful]

This has happened to me after I put some white dial faces in.

Thing is the mental needle calms down after about 60 secs (after a cold start) and is then fine?

Any ideas?

Edited March 19, 2011 by Tony de Wonderful

[SL33K]

Me i thinks that the problem is just a simple one. we are just missing it.

There is something we are doing when when taking off the cluster that temporerly fixes it, as most people say it works after removing cluster to fix the tacho and then the problem comes back.

mine even behaves properly if gently push the glass thingy inwards slowly. Why would it do this if its a problem with a capacitor or IC or something on the tacho IC board thing.

I think i am gonna take mine out tomorrow and look on the outside. BTW is it safe to start the car with the dash cluster out?

[Tony de Wonderful]

Finally got around to doing this one on the weekend and my tacho is still playign up

my next move will be to resolder all the contacts. Im guessing there is a possibility that a contact is not secured to the PCB anymore.

If i cant find anything ill probably bite the bullet and buy a new cluster.

or maybe a tacho from nissan if there are any left...

You need to de-solder the main chip on the Tacho PCB. Once it's off you remove a bit of the green 'solder resist' from the PCB where the chip's legs are soldered. You then solder the chip back on.

This gives the chip better contact, and it fixed my problem anyway.

There is a tutorial on www.Skylineowners.com but I can't be arsed finding it.

[FrankoR33]

Heys guys, i was also racking my brain over this as mine has been doing it for quite some time that now it doesnt even flicker just stays over 9000 dead so i pulled my dash off and pulled the cluster half out and all i did was unscrew the screw just above the right hand black loom (looking at the tacho face on) be careful not to drop the washer and lose it, i was tempted to go get some contact cleaner but for now thought id just wipe it with a clean rag, put it back together and now it was flicking around 4000 so i knew i was on the right track, i found that some of the other screws were a little loose so i tried to do them all up at an even tightness because i found if one was too tight it would flicker even worse, so get them nice and even then i put my cluster back in GENTLY so hopefully i dont bump anything and make it go crazy again, it idled fine so i took it for a drive so far so good, revved to 8k and back still good.

I know this sounds ridiculously simple but thats what has fixed mine im sure everyone might have a more complex problem im just throwing out one solution for now, will update if it plays up again in future.

Bryce.

[FrankoR33]

Well unfortunately mine has started playing up again, so its obviously a bit more complicated than i first mentioned, oh well might be time to upgrade my cluster anyway

[Kinks]

the problem's a failing cap, a scratchy pot or a dry joint on the board, if you unscrew it and screw it back in again it *may* make slightly better contact but as soon as you leave your driveway it's going to work itself back to intermittent contact again. by pulling it all apart and putting it back together again you've jiggled the board around a bit but not really done anything meaningful towards fixing it.

after I fixed my tacho it has been 100% perfect ever since.

[MatthewT85]

huge thread bump but....

went to jaycar today and the closest one they said they had has 153k100 on the top, it doest look like the ones posted above, will it work or should i just buy a pack of 50 from ebay of the correct one?

EDIT

or is this the one i need?

http://www.jaycar.com.au/Passive-Components/Capacitors/Greencaps/0-015uF-15nF-Greencap-Metallised-Polyester-Capacitor/p/RG5075

does it matter that it says 100v?

Edited September 29, 2015 by MatthewT85

[Kinks]

153K100 means 15nF +/- 10% 100V.. so it'll work fine (so will the one you linked).

probably the other common types for 15nF would be ceramic disc (orange) or MKT (a white square shape). MKT is closest to a greencap, a ceramic capacitor will change capacitance with temperature so may produce weird results. I must admit I didn't look too closely at how that capacitor was used in the circuit, I just changed it with the same type. Maybe the exact value of capacitance does matter, maybe it doesn't.