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MG TD TF 1500 - Behavior of tachometer

I never have seen a British Jaeger tachometer in action.

When I'd bought the car, the generator didn't have an adapter for the gearbox. I was able to swap to a C40 and to repair the gearbox. Also I'd ordered a new drive cable.

Then I connected the drive cable to the instrument (at that time I wasn't aware that the tachometer is based on a chronometer). It did not seem to be correct. The hand jumped and after a while it stuck at 1000 1/min and didn't move anymore.

After that I gave the instrument to a workshop for instruments with a really good reputation. The boss shook the instrument and a rattle came out. It was a broken tooth.

Yesterday I'd installed the instrument. I was surprised because the instrument showed (for me) a strange behavior. It was nearly as before the repair.

The hand jumped in gaps between 1000 1/min and after stopping the engine the hand resided at nearly 1000 1/min.

This morning I'd reported to the mechanics. He told me this behavior is normal for an instrument with a chronometer inside.

Is this the truth? The speedometer is based on a chronometer too. But the speedometer doesn't jump with such gaps.

What is the behavior of yours chronometric tachometer?

Bela

Bela,

The increments of the chrono are small. An increment of 1000 seems way too much for me.

Jasper
JL Nederhoed

Could be the cable needs lubrication or the inner cable is kinked.

Tim
TD12524
TW Burchfield

Hi Tim,

the cable is a new one.
Bela

To prove where the problem exists, connect a variable speed battery drill to the back of the tacho and see if you have the same jerky respnse.


Graeme
G Evans

And run it in reverse!
Regards
Declan
Declan Burns

The problem is solved.

I've been dazzled and I've been too careful when I stopped the engine immediately while the hand jumps during dynamic throttle.

I went to the workshop and the chronometric instrument was connected to a test equipment. I could see, that everything is okay and the hand is stable during normal acceleration. It is also normal that the hand stops above zero if the engine stops fast.

Now installed back in the car I'm glad to see the revolution of the engine.
Bela

This thread was discussed between 18/04/2016 and 19/04/2016

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