Where to get a replacement Tachometer for 84 911?

[eflight]

The tachometer in my 84 911 Targa isnt working properly.

I sent it to Nichols Speedometer & Instrument (NSI) for repair but they were not able to fix it.

So is there a reputable source for a replacement tachometer?

A good used one would be fine with me.

TIA

[esample]

I have one from an ‘86. Works perfectly but I don’t know if it will work on your car.

-e

[mikesarge]

I’ve got one for a 1980 sitting in a box I’d sell you, but like esample I don’t know if that’s the right one for your car.

Hookups are + - and TD (low voltage square wave signal)

[7783911]

Try JBELL on this forum

[GH85Carrera]

Send it to someone like Palo Alto and have them add a voltage meter to it, and repair the tach. Score!

I love having my voltage meter right in front of my face.

[PeteKz]

I had John Bell do mine. Put a voltmeter in the bottom of the tach, just like Glen's above. Love it.

[Rodsrsr]

Plus one for JBell. He does fantastic work.

[eflight]

I'm in the same postion as you guys, I dont know what other years would fit the 84.
I think the 86 since its a 3.2would, but not the 80.


Do you guys mean jbell959 ?

thanks

[mikesarge]

yeah, Jbell959 is right. he's gonna be your guy for this

[MrBonus]

Another vote for John Bell as he does amazing work and, as others have mentioned, can modify it nicely if desired.

[eflight]

thanks guys, its off to John on Monday

[eflight]

Just got my tach back from Jbell.

Tachometer looks great and looks like its working correctly now. Cant take it for a drive as I have the shifter all apart, but was able to start and rev the engine and its functioning correctly.

NSI had it for almost 2 months and was unable to repair it

Jbell had it for about 4 days and fixed it

Thanks to all here who referred me to Jbell

Now on to getting the sifter linkage all put back together.

[IU89]

Sent jbell959 a PM and hoping to hear back. same issue, was told these can have internals that get old and can stick.

Is the removal and re-install complex?

Appreciate any insight that can be provided.

Cost?? roughly?

thx

[pmax]

Originally Posted by eflight

Just got my tach back from Jbell.

Tachometer looks great and looks like its working correctly now. Cant take it for a drive as I have the shifter all apart, but was able to start and rev the engine and its functioning correctly.

NSI had it for almost 2 months and was unable to repair it

Jbell had it for about 4 days and fixed it

Thanks to all here who referred me to Jbell

Now on to getting the sifter linkage all put back together.

Don't mind my technical inquiry but ...

what was the failure mode and the fix if known ?

[darrin]

pmax -- around 20 years ago, the tach on my '86 failed due to my not recognizing voltage spikes caused by a failing voltage regulator. Palo Alto speedometer fixed whatever in it was fried by the over voltage and it's been fine ever since

[spuggy]

Originally Posted by darrin

pmax -- around 20 years ago, the tach on my '86 failed due to my not recognizing voltage spikes caused by a failing voltage regulator. Palo Alto speedometer fixed whatever in it was fried by the over voltage and it's been fine ever since

I understand (IIRC, old thread by Grady, RIP), that both the speedo and the tach were fitted with 15V electrolytic capacitors originally.

Not only do these not like being continuously supplied with voltage substantially above 15V, but these capacitors have a finite lifespan and can also simply fail from age (common reason old PCs and guitar amps stop working). Many repair places will replace these capacitors with one with a higher voltage rating, like 25V, instead...

The "classic" symptom of a voltage regulator dying is voltage spikes causing spiking tach readings. However, some VRs simply stop working altogether (and give 18V unregulated output) with no spikes. My tach never spiked - only clues were a measured steady 18V across the battery terminals at idle when I noticed a huge fuzz ball growing on the battery post....

Couple of years later when it failed entirely, turned out that the odd speedo behavior (needle jumping around and not reading constant speed) I'd noticed since was likely that being damaged from the VR going south - as a replacement gave rock-steady readings.

[spuggy]

Originally Posted by esample

Works perfectly but I don’t know if it will work on your car.

Older tachs (74? about there I think) require a higher-voltage signal than the later ones. You can adapt these with a tach adapter. Or wire the coil of a relay in-line with the TD pin - EMF generated as the pulse collapses gives a "fat" enough signal to drive the older instruments.

I believe John Bell fits a tach adapter board as standard.

Anything later (eg after ignition changed to CDI?) is pretty much interchangeable between any F/G body car, I think.

Another shout out for John Bell - tach and boost gauge both his work:

[jgurnari]

mine is a 1985 911
the issue is, when cold the tachometer does not move, sometimes stays lower than 500 RPM, just sits still. after driving for maybe 20 mins it starts working as it should. any ideas? thanks