My fix for intermittent tacho, speedo etc..

[sparkgap]

I\'ve read lots of messages about crazy tachos, speedos that seem to remember they should be metric, odometers that go on the blink and stuck fuel gauges.
The easy but expensive fix is to replace the cluster.
 
I had all the above on my \'92 FD and managed to get everything working, the cause.. capacitor plague!
Look it up on http://en.wikipedia.org/wiki/Capacitor_plague
 
On my car the PCB behind the speedo had two radial electrolytic capacitors with the plague i.e. domed tops and signs of electrolyte leakage down their legs.
 
I decided to replace all the capacitors as most were from the same factory.
 
Total cost of repair, less than £3 thanks to a couple of evenings in the living room desoldering and replacing them. About 7 of if my Christmas memory serves me right!
 
On another forum I read that the tacho can develop dry joints on it\'s PCB so I stripped it out but could see none. While it was out I reflowed the solder joints just in case.
Note that to do this without losing calibration requires a special procedure which I could explain if anyone was interested as you have to remove the needle.
 
I occasionally got a random beeping from the EL unit when the car was cold so I checked that as well, lo and behold there was a plagued cap too!. Replacing the caps on that did not fix the beeping problem although I was unable to immediately replace the 2 non-polar ones.
 
I guess if any cars with the cap plague are found then the whole lot, including ECU might need replacing to prevent future failings. I just got an Apexi after a two year wait for a rebuild so I\'ll never know.
There may well be other modules in the engine bay.
 
If you want to try this fix then be aware that you\'ll need to be good with a solder sucker and soldering and have really hot (no.9) iron as the PCB behind the speedo is double sided and melting it all the way though to the other layer is difficult without the capacitor leg in there.
Even with a hot iron it\'s quite tricky to remove the solder with a sucker from the tiny copper tubes between the layers after you get a capacitor out. Ideally you should use two irons, one for each side and a third hand to operate the sucker.
 
Admittedly the fuel gauge may not have been fixed by this process but while it was accessable I noticed that the actuator shaft is damped more than any other, perhaps by a thick silicone grease. My gauge seemed \'overdamped\' and it might have got stuck, so I just moved it up and down repeatedly (but gently) about 100 times which made it move a bit easier now.
 
Martin

[Initial-D]

Well I have all my dash out so I\'ll go and have a look!

[sparkgap]

Nice skirts!

[sparkgap]

Bumping this, a few other threads have mentioned probs lately.
 
And just found this http://www.rx7club.com/showthread.php?t=599220&highlight=speedo
 
I am still looking for the component level circuit diagram of the
cluster.

[Joeh]

My two dashes I fitted doesn\'t work. Both don\'t show the coolant level, fuel level, oil level, RPM etc but the lights work?! O_O;

Something to do with the wiring I guess.. but the dashs both work on other cars .__.;

Any idea what that could be?

Had a APEXi PFC which got removed recently and put back with stock ECU... anything related?

[sparkgap]

Have you checked the fuse? (METER 15Amp)
 
Otherwise see that power is getting to the back of the cluster with the ignition on.
Pull out the cluster a bit and check that there\'s voltage across one or more of the gauge screws indicated in this pic while it\'s all connected (you might need a friend to look through the windscreen to guide you).
 
I think the ECU retrograde causing the fault is unlikely, why change back BTW?
Martin.

[Joeh]

Sorry, Yeah I checked the fuse... I don\'t think its a power issue as the red light for Water sensor comes on and oil pressure at auxilary... and for some strange reason, in auxilary (before starting) the RPM guage goes up to 1000rpm?! O_O; when I turn off ignition after 10 seconds the RPM guage slowly goes down again... strange?

With regard to the APEXi ECU.. it wasn\'t me who changed it back.. it was the previous owner Just a few days before I bought the car from him >__<;

Anyway just incase I\'ll try test that today I managed to get the oil pressure working, but fuel RPM and Water Temp/Water sensor isn\'t working still.. I\'ll have a go when I get down to the garage

Thanks

[shaggy]

My dash has started getting these problems, just rebuilt the engine and now they won\'t work. Not checked the speedo yet but Tacho flicks on aux ignition but registers zero when running, water temp is not working, boost is not working, and fuel seems a bit low but off the mark.

Any ideas?

[Prof]

Little tips on desoldering components:
 
1) use a small tipped iron - on a good heat - say 330-360C for desoldering.
 
2) Make sure the iron is clean (that ghey sponge that comes with a lot of soldering iron kits - you need to wet this and keep wiping the iron tip on it till it shines).
 
3) Hold the iron on the solder pad until the solder melts - you will see the surface change when it does.  You can do this from either side of a double sided board, but I find it easier to work the iron from the bottom side as there are fewer components in the way.
 
4) Once the solder melts, use a small pair of pliers or tweezers to extract the component.  Don\'t worry about leaving a perfect hole just yet...
 
5) Using fresh solder, reheat the pad again and allow the solder to form a nice looking mound (it should be concave not convex or ball shaped) and then whilst the solder is still molten, use the solder sucker to remove the solder from the hole.  This seems to work much better as there is more solder to suck on and it tends to want to stay stuck together so it comes off better.
 
6) On wide tracks or components with heatsinks attached, they will dissipate more heat, so you need to keep the iron on longer, or up the temperature - for really big solder joints use a bigger iron as it has more thermal inertia.
 
7) Delsoldering braid doesn\'t really work that well - Get the pump action sucker - but keep cleaning it out and also don\'t leave the tips in contact with the iron or a hot pad for any longer than is necessary - they get manky pretty quick and no longer form a good vacuum.
 
Practice on rubbish circuit boards first - it\'s less costly if you are just learning the techniques !  You can find plenty of old telly\'s, PC\'s and radio\'s on rubbish tips these days.