Finally! The REAL fix for a bouncing tach
 

So after a couple years of dealing with my tach in the car bouncing around every now and then (some intermittent fault/short) I decided to pull the cluster and see what was going on. So I noticed there was a 1000uF electrolytic cap on the tach circuit board itself that looked like it had leaked (common problem on circuit boards).

http://lh4.ggpht.com/_OXFQfeHs-8Q/Sx...0/IMG_1373.JPG
http://lh5.ggpht.com/_OXFQfeHs-8Q/Sx...0/IMG_1374.JPG

So took the old/faulty cap to the local electronics store to get a replacement. The guy there says: "yeah, seen lots of these, apparently the company that made them stole 90% of the electrolyte formula from a competitor and made these sub-standard caps, and obviously these things were prone to failure because of that"

So the unfortunate part is that either some or all of our tachs may eventually have this issue because of this, depending if Nissan used the same supplier for all model years. Most likely it will just be a subset of the 3rd gen population.

Crazy eh? So soldered a new cap into the tach circuit board, and all is well... no more bouncing tach. This is not a particularly easy job, since it's hard to get a soldering iron access to the cap area on the board, but if you have some skill and some patience, I would say it's probably a 3 out of 5 difficulty rating.

I used a coffee mug to support the tach body so not to damage the needle.
http://lh5.ggpht.com/_OXFQfeHs-8Q/Sx...0/IMG_1376.JPG

I have heard of people having similar issues with their speedo as well, so this may be the same problem. The speedo board has several electrolytic caps on it also, although it didn't look like any were the same brand or as large as the one on the tach.

:doublethu

if anybody read the stickies anymore, i'd say sticky this!

awesome, im gonna check this out on both my VE's since both cars speedometer needles dance around

good to know, my RPM gauge is fked and its probably because of that. If it werent for me doing the digital gauge or 280z pod gauge swap i would fix it

Looks like I have to take a look onto that as well. I swapped the gauges on my 89 to the 94 GXE gauges and it occasionally has the jumping tach behavior.

Please update us in a week. Ive pulled my cluster many times and once did nothing but poke around and wiggle stuff then put it back in and no more bouncing speedo.......for a week, then it came back. But if this is the fix, I have 4 clusters to solder!

Nice work. I linked this thread in the general maintenance sticky. :)

I am experiencing the bouncing speedometer issue, so I may need to pull my speedometer unit out and take a look as well. I have never used a soldering iron before, but this may be a good reason to learn.

Wait? You busted a cap on your tach?

I read somewhere that electrolytic capacitors have less life than the ceramics. It's no help if reverse current happens, but don't quote me on that. But in time we should replace all of them.

How hard is it to pull your cluster out? I've been having problems with my temperature gauge and gas gauge acting with a mind of their own...

fairly easy from what I remember, but it has been years since I pulled out a cluster on a 3rd gen.

pulling the cluster is a 5 min job. need a small flathead screwdriver to pull trim pieces, and a couple different lengths of #2 phillips screwdrivers.

i'm wondering if temperature affects it? my RPM needle has bounced for over a year, and this summer it worked maybe 1/10th of the time but since its been freezing cold outside it's been constantly working fine?

and yeah, to take the cluster out, take out all of the trim screws with a phillips and pop off the AC vent cover with a flathead (goes from over the left of the steering wheel to the right), and theres some screws holding the speedo on. unscrew them and it comes right out. took me ~20 minutes to remove a digital cluster from a junkyard Brougham 3rd gen for my cluster swap and that was my first time removing one

I think temperature does affect it somehow... mine was similar, was way more wonky in the summer time, and since it's been colder it's worked pretty much all the time (before I fixed it).

Nice job, never knew tachs were a common problem on the 3rd gen... I've owned mine since 05 and never had a problem with it, lets hope it stays that way :hide:

Just an update for everyone... this definitely seems to have fixed it! Since I did this, I have not seen it bounce once, and it's cold out now so it should've been doing it all the time. :thumbsup:

In addition, I came across this site http://www.wrex-racing.com/docs/fd/Tach_Repair.pdf where a member with a '95 RX7 did the same fix, and incidentally, if you look at the pics in the PDF, the RX7 has an IDENTICAL tach to the 3rd gen (must have been the same manufacturer). He ended up soldering all connections, but likely just replacing the electrolytic cap (the big one) should be enough.

Also, it's probably worthwhile to add that you should clean up the main ground going to the engine from the battery, as well as the two ground connections on the manifold (for VE anyways) as those drive the camshaft position sensor, which is how the computer reads RPM. Also worthwhile cleaning the CPS connector. Any little bit of corrosion could lead to noise, which could affect the CPS as well as the tach (VERY sensitive to electrical noise). Use some dielectric grease once clean to help protect from the elements.

I haven't done any research as to whether this affects the VE more than the VG, since the VG has the CPS built into the distributor, but might be worthwhile investigating for those with VG's. In either case, tachs are extremely sensitive to electrical noise, and I recommend the cleaning of the grounds should be done first before tearing into the dash.

Hahaha, yeah, that is true... over time, the electrolyte can leak out, and then not only will it eat the circuit board (acidic), it will render the cap useless. They have a fairly long life, though sometimes they do die, especially when they were substandard to begin with. :)

Crappy camera phone pics (I miss my Samsung U-600 :() but I changed the cap on my tach today

http://img695.imageshack.us/img695/3950/dsc00114k.jpg

Unfortunately I wasn't paying attention and the soldering iron touched the outside of the gauge
http://img689.imageshack.us/img689/1011/dsc00113b.jpg

It's not that noticable when everything is installed, but I hope just knowing about it doesn't irritate me as the squeaking of a polyurethane bushing :mad:

So far so good. I will come back in a week report on status.

Heheh, at least it wasn't your skin or the iron's electrical cord:p

Board will not be eaten by leaked electrolyte, it's not the same as battery's. Much more often than anything else they 'dry out' so to speak - electrolyte changes its properties over time without leak. As a result capacitance decreases rendering it completely useless - as you said. This effect is also temperature dependent - the higher the temperature the faster process goes in general.

Didn't work for me :( In 6 days it started jumping on me again.

http://img69.imageshack.us/img69/8708/dsc00116d.jpg

I will take another look at it when I get the chance.

Thanks for reporting back, and good job on actually snapping a pic of it... from all my research so far, the cap is just ONE issue with these tach circuits. Jbbons25, definitely try and clean-up the ground circuit from the battery-to-chassis-to-engine. At least on the VE, this is a crucial circuit for the camshaft position sensor which the ECU uses to determine RPM. It's likely similar on the GXE, but it uses a sensor inside the distributor instead. However, in both cases, the ground connections are really important, since the tach signal is EXTREMELY sensitive to noise.

Check and clean (with 600 grit wet-dry sandpaper) and apply some dielectric grease to these terminals:

http://lh5.ggpht.com/_OXFQfeHs-8Q/S1...und%20wire.gif

Since I did the fix, my tach has been perfect, and I keep an eye on it all the time, and have never seen the bounciness return. But my connections were also clean and greased. Let us know how it goes.

Good work.

You did a great job.

damnit...wish i hadnt bought a tach before stumbling across this thread.

Thank you. I fixed my rpm gauge. :D
http://s18.postimg.org/4omoc7v7p/20140920_164040.jpg

Hey man, sorry to hijack the thread...but I have the same issue with my car. It's not a Maxima, but it is a Bluebird (same thing?).
It's a 1996 Nissan Bluebird SSS model (engine SR20DE).

I had a look at the tachometer circuit today, but couldn't find a capacitor like the one you mentioned. I did find one that had 1000 and 16 written on it, but not like the one pictured.

Would that be the culprit? I couldn't see anything that melted, or any clear issues - but I still have the bouncing tachometer. I sprayed it with electronic cleaner just in case.

I also broke the little plastic cover infront of the instrument panel - is that a universal fit, or would I need to get one suitable for my car?

Thanks in advance guys!

Getting the bloody thing out of the dash is the hard part for me. Soldering is cake.

Genius!