'71 XKE S2 Tachometer

Hi All,

I am in the process of assembling my friends XKE S2.

I had all of the gauges rebuilt by Nissonger. I recently started up the engine, and the tach is acting in a very sporadic nature…

What do you guys think? What could be the issue?

When I start the engine, the tach seems to read a steady reading. As I reduce the choke, it becomes erratic?

Here is a link to a video of the tach when engine is warmed up. Please let me know if you cant open and/or see this.

Thanks! Bob

What ignition? Loads in the archives.

Yeah, ^this^. Non-stock ignitions (e.g. Pertronix) don’t always play well with the S2 tach.

Which side of the ballast resistor are you running your ignition red wire from dustributor?

My 69 with triple cards and pertronix required the tach to be rebuilt to accept the pertronix signal

My 69, with triple SU, and pertronix did not have to be reworked, but it needs to run with the full 12volts, not through the ballast resistor.

Hi Team,

I am not running on Pertronix. I am on a Mallory dual point distributor.
Thanks, Bob

If you are running a Pertronix (solid state ignition) it will never work properly and be accurate. Nisonger will rebuild it with all new internals to except the solid state ignition. They did mine after the same problem and it had worked great ever since

Sorry, just updated my earlier post… left the word “not”…

Not running Pertronix, running with a Mallory.

Thanks,
Bob

Hi Karl,

I have the ignition wire (distributor) plugged into the front of the ballast. See attached picture. I looked again, and do not see any markings on the ballast?

Should I switch the wires? Thanks Bob

Oddly, I am running a Hot Spark ignition (basically a Pertronix knock-off) and the tach works perfectly (69 S2).

https://www.ebay.com/itm/Electronic-Ignition-Conversion-6-cyl-Lucas-23D6-25D6-Distributor-Rover-Austin/323752612107?epid=1934071532&hash=item4b6128d10b:m:miUIKxb78HwBd2Ez0vG_aSg

I do not think switching the wires end-for-end on the ballast would make any difference as it is just a resistor.

Take your distributor wire direct to the coil, your “run” wire will still go through the ballast resistor. This worked for me, but I don’t want to state with certainty that this will work for your setup.

Karl, are you saying to remove the distributor wire from the ballast? Basically leaving one end of the ballast open?
Thanks Bob

Hello George,
After I installed the Pertronix in My E-Type at first the tach seemed to read fine. Then after a while (I don’t remember how long a while was) it started to really act up bouncing all over the place. I then read an article from Nisonger as to why the original wouldn’t ’ work with the Pertronix. There was nothing mentioned about any other distributor. Anyway I sent my Tach to Nisonger and made the wiring changes they recommended which was simple and it has been great for the past 4 years.

You should have a hot 12volt wire that powers your coil once your engine is running. That wire passes through your tachometer, then connect at one side of your ballast resistor and produce about 6-8 volts to your coil. Your distributor wire should connect to that 12volt wire before it passes through the ballast resistor and goes to the coil. I used a double spade clip at the 12 volt side of the resistor to join my hot wire and distributor wire. I then made a short jumper wire to go from ballast resistor 6volt side to coil
.

Hi Bob…no one has mentioned the sound…i hope its just the michrophone…it sounds like a tractor…Ballast cct may help you

Yup. Hard to get an accurate recording of a running engine without a good mic.

I had to have my tach converted when I installed the Pertronix dizzy. One of my tachs. I have a spare ‘68 E-type tach, which is unique for its 5500 redline. Both refused to work with the new distributor. I contacted Nissonger on researching the archives and they were pretty backlogged, like 6-7 weeks, but would fast track the job for extra $$, saying it would still be 3 weeks plus. So I contacted West Valley Instruments who promised a one week turnaround at considerably less cost. Worked great and delivered as promised, so I have no qualms recommending them. Morris Mintz is the man’s name.

X2, especially since my adventure with Nisonger (speedo rebuild and calibration) was…

…okay, I guess I cannot say what it was but yes, Morris is the man.

Hi All,

The tach issue turns out to be a wire issue. The wire that I ran from my tach to the coil is faulty. With a new wire, I get a perfect reading of 800 rpms.

Thanks, Bob

Hi All,

Well, while the tach works at idle, when I reach approx 20 mph, the tach needle becomes erratic and drops to zero.

I have the tach and ballast wired as per MGCJAG’s diagram above.

The negative side of the coil connects to the distributor (white/black wire). The positive side of the coil connects to “C1” on relay 33231 and also connects to one side of the ballast (blue/white wires). The other side of the ballast connects to the tach and also the ignition switch (white wires).

Any ideas on what the issue could be?

Thanks! Bob