Tachometer quite working

[Swank911]

Looking for a little diagnostics help. Over the last few days my tach needle has been floating around, would drop to zero rpm, then bounce back up to around the correct rpm for a but never stay there, it would float and bounce around. Yesterday the needle dropped to zero and did not return.

The engine sounds fine, runs fine and I have not other issues.

The tach is original to the car, 73, 2.4L MFI, but was modified by Palo Alto when we swapped the engine for a 3.0 CIS to get signal from the CDI.

I am wondering how to make sure it is getting signal and determine if it is CDI output, wiring or an issue with the tach itself.

[Flat6pac]

I dont know what the tach repair company would have done to get the count working because setting up the tach drive is part of the install.
Removing the 14 prong connector from the engine side, open it up, pull out the black/purple and jump it over to the chassis harness will give you tach drive.
Bruce

[unclebilly]

Turn on your head lights - does the tach illuminate? If not, your ground wire going to the tach is loose. There are 2 wires that connect to a common spade connector on the bottom side of the back of the tach - these are the ground leads.

[deathpunk dan]

that is some awesome advice uncle billy, seeing as how I'm in the same boat as the gentleman who started this topic (I will be running out to the garage in a moment). I never even thought to check the ground wire!!!

[unclebilly]

Same thing happened to me last night and I fixed it at a gas station...

[Swank911]

Thanks Guys, I will check this tonight when I get home.

This could explain why the needle was floating.

The conversion I had done was to pick up signal from teh CDI with the CIS, the MFI set up sent the signal from the crank/rotor.

-Jon

[Swank911]

I took the advise and turned on my head lights, Tachometer lit with no problems. Turn Signal indicators and hi-beam indicator work as well.

Can I use a multi-meter and jumper between the tach input (purple wire) and the ground crimp to see a signal is being sent to the tach? If so, what would I see on the multi-meter?

Thanks

[scarceller]

You really need a scope to check for tach signal. But maybe a LED test light might also work. Do not use a normal test light only a LED test light should be attempted as it requires very little current to turn the LED on. You should see the LED flicker if you have signal.

You can get a $3.00 LED test light at Walmart in the Auto section. I have one of these from Walmart and have seen them in many Walmart stores.

Best of luck.

[Swank911]

Thanks Scarceller,

I will give it a try. If I do get signal, does anybody have recommendations for someone to repair the tach? I would also like to send out my clock and fuel/oel gauge as I have condensation inside the glass.

Thanks again

[scarceller]

try these guys http://www.nhspeedometer.com/

[PCA7GGR]

+1 on North Hollywood.

My tach began to function oddly (random or no readings). After insuring that the voltage regulator, alternator and wiring were in good working order, I sent the tach down to North Hollywood last Thursday. I got a call Monday from them advising me that the tach had a old, bad circuit board. They will have it fixed and on its way back to me before the end of the week.

I had similar service on an early cable driven speedometer.

[Swank911]

Thanks Guys, I will give them a ring this afternoon.

[Swank911]

I am testing for signal from the CDI, could I use a mutilmeter to test amperage from the CDI?

What should I see? Amps or Mili-Amps?

Could someone also confirm what I have seen in the wiring diagrams? Black purple is connected to the first spade and the browns are connected the spade with "C".

Thanks

Jon

[2Utes]

With your engine swap, I am not sure if this will help you or not. My stock 82SC developed a floating tach last week. My searches on this site indicated looking for ground issues. I found mine at the ground connection under the passenger seat and the CDI(?) box. I cleaned the ground connections, and the round multi-pin connector on the little box attached to the CDI box and everything is back to normal.
Good luck chasing your issue down.