Tachometer

[Robin260z]

Hi guys my tacho isn't working either.

I;ve read a lot of posts trying to figure out what the problem is.

I;ve already read that i have a 4 wire tacho that isn;t original because a 260z normally has a 3 wire.

But all the wiring is original so thats also weird.

tha tacho gets good ground and 12 volt.

The ignition signal is ok because when i disconnect the connector the car wont start because it is a circuit that has to be closed.

So could someone give me the right electrical scheme for a 4 wire tacho or tell me how i can repair/ rebuild my tacho.

Sometimes it starts to work for a few minutes but it can also dont work for a few weeks.

Could it also be the resistor? where can i find this in a 75 260z 2+2 ?

thx guys

[Travel'n Man]

I have been battling the tach question for the past several months - I have bought a couple tachs off ebay with no luck with none working correctly. Last year I completed an engine rebuild and upgrade to electronic ingition and fried my perfectly good tach. So after several bad ebay purchases I made up my mind to have my tach rebuilt here:

http://www.gaugeguys.com/repair.htm

I just got my tach back last week and yesterday re-wired per the new set up and instructions from the rebuild shop - three connections:

1 - 12volt

1 - ground

1- negative side of coil

I left the original set up all connected and ran alligator clips for the set up above - direct battery connections and direct coil connection -

No start -(I then plugged into the 4 pin connector one that I had that has in incorrect RPM reading and the car fired right up so I know the rebuilt tach is the problem) so I called the fine folks up at APT Instruments and an shipping the $215.00 tach back to them so they can address - somebody needs to figure out a rebuild for our tachs so we can plug and play and have a normal correct reading. Don't mind to pay the money, but I want the damn thing to work after dishing out the bucks..............

Anybody had any success out there??

[260 z]

my car was built may 74 and is a 260 coupe, it's tach go to 8000 when the key is turned on. I have a posting here and in member's only but still have not found a solution to my problem.

Here is what I have found out.

There is a company nhspeedometer.com (per another thread) that can repair the old tach or put new internals in the old case.

My tach is original and is a three wire plus the four wires to the lights so it has a seven pin connector

I get from the dash wiring harness, 12 volts from the green wire, 2 volts from the red with black strip wire, and a good ground from the black wire. I just don't know if that is correct?

An old thread I read ( on a 240 ) said their problem was a broken or bad or unconnected wire in the engine compartment. It was the black going to the coil. When I checked my harness at the coil, my black goes to the center terminal of the ballast resistor, the black with a white strip goes to the one side of the ballast resistor,and a black with a green strip and a white with a black strip goes to the other side and then up to the negative of the coil, the final wire at this point is blue and it goes to the positive side of the coil. Is this correct??

The resistor is located on the passengers side just behind and or below the glove box. It's about two and a half inches long in a clear plastic casing.

I think these old cars have a lot of these types of problems...that is why these forums are so helpful. I hope this helps you a little and someone reading this can shed some more lite on this whole tach issue. I don't know if I have a tach problem or a problem some where else in the wiring ??

Edited March 13, 2011 by 260 z
wrong colors on wires

[LeonV]

I have an early 260Z and my tach did the same thing, jumped to 8000rpm with ignition on. However, the PO made a short in the circuit when wiring in a start switch (to fix the solenoid click, no start issue). After I removed the switch and reconnected the old wiring the tach would work intermittently, sometimes I'd have to tap on the housing. Then it pretty much stopped working so I figured something got fried inside. I took it apart and looked at it, no multimeter involved, and noticed nothing that would indicate damage. Just got a 280Z tach off of ebay so I'm hoping that solves my problem.

[260 z]

:stupid: After I posted and read robin 260's posting, I went back to check my connections. It was as I posted but that is WRONG. I put in a XR 700 module and when I reconnected to the coil, I got it backwards. The Blue wire goes to the negative and the white wire with a black strip goes to the positive. I changed them and the car still starts and the tachometer still goes to 8000 when the key is turned on. Oh well, I'll keep plugging along.

[260 z]

I just spoke with nhspeedometer and they said special testing meters are needed to test the tach out of the car. I told them that with the key on, I was getting 12 volts from the green wire and the red with black strip had about 2 volts. After the motor was running, the red with a black strip would vary from 4.5 volts at about 800 RPM and 7.5 volts at about 3000 RPM. They said that my wiring harness seemed to be OK. I will be boxing up my tach a sending it to them. If it needs rebuilt, their estimate is $ 185.00 plus freight.

[Travel'n Man]

Refer to post #2

Packaged my tach up today to UPS'd back to the repair shop - scheduled to get there on Thursday - stay tuned - we will see what happens to this tach...............................there must be a better way!!

[260 z]

Travel'n-Man did you ever check the voltages coming from your harness??

Is your original tach a 3 or 4 wire??

I will be sending my off tomorrow so we can compare notes

[tlorber]

I had my '73 done by North Hollywood Speedometer. The original thread may have been a post I did a while back. As I stated, I took in my tach and they replaced the guts with new solid state that recognizes signals from different sources (wave forms). This means that you can use the original dizzy, a newer electronic one, pertronics-whatever. I asked them if they were SURE it would work when I brought it in and they assured me it would. They were right- the thing has been bulletproof for about a year now.

Rather than trying to find a replacement on ebay that may be just as bad as the one you have-or from a different year, I strongly recommend having the original rebuilt. The new electronics are also much more accurate than the originals ever were.

[Travel'n Man]

Todd - can you tell me how the re-builder had you wire your tach please.

[Travel'n Man]

Alright group - he is the close to this issue

1) Have your tach rebuilt - I used Chuck at www.gaugeguys.com

2) Dish out some bucks to have the work completed - $215.00 includes freight

3) Remove your pin wiring from the rear of the tach when you get it back

4) Plug in your removed 4 pin connection and zip tie out of the way behind the Tach housing (this way your loop in connected)

5) Make you 12v / ground / negative side of coil connection

6) Fire up your car and your tach is solid and good to go

7) Remount your light connections and turn signal connections

8) Check to make sure everything is working

9) Lay upside down and reconnect your wing nuts and then have anice glass of Balvenie Doublewood (light on the ice please) 12 years - Jack Daniels Oak cask and a Sherry Oak Cask for fantastic aging!

If you car does not fire make sure you have your 4 pin connector well seated to make your loop connections - make sure you connection is clean at your negative side of the coil.

[260 z]

Today I installed the rebuilt tach from nlspeedometer and it worked great. They used the plug from the original tach so you just plug it back into the harness