tachometer not working

[planes49]

My tacho has never worked, and I havn't really been bothered by it. However would now like to have a go at fixing it. I see there are 3 wires (plus lighting) fixed to top back of instrument. The black central is I believe the earth, the black/white goes to the coil, and I'm not sure about the green. Does it go to the ignition?
I did aquire a spare tacho and tried fitting that, with no luck, so it appears not to be the instument.

[Penelope Stopit]

Yes that's it, green is fused ignition

[fieryfred]

My problem was at the coil. Check the connections & move the king lead out of the way.
That played havoc with the signal.

[Penelope Stopit]

fieryfred said:

My problem was at the coil. Check the connections & move the king lead out of the way.
That played havoc with the signal.

Interesting

[Belle427]

The wiring at the coil does get a hard life, it’s pretty easy to carry out a continuity test on the cable in question.

[Steve_D]

Yes continuity check the wire. Don't be fooled by the fact it is white/blue at the coil and white/black at the tacho.

Steve

[planes49]

Thanks all. Have been out playing with the car this afternoon. The coil has a white wire either side at bottom, a black wire on top nearside, and black/white on top offside. The wires then disappear into a very complicated looking connector, before going into loom. Am thinking of running direct wire from the top offside connector on coil to back of tachometer?

[planes49]

I have finally got back to playing with my wiring/tachometer. R-tried my spare tacho, and hey presto, I now have a working tacho. Can't have wired it up properly when I checked it about 3 years ago. Now to investigate my recently misbehaving water temp gauge.
Incidentally, if anybody wants a white tacho with black figures for a rebuild etc, very happy to post it out if it can be of use.

[QBee]

What's the issue with your water temp gauge?
There have been many threads on this and we may have a good solution for you

[planes49]

Basically, it has stopped working. It used to run a bit hot and I did the paper clip thing with the otter switch. Have now put it back to normal. Took it for a run this afternoon, hot air from the heater, and the water pressure tank hot, so thermostat is working. I havn't had a look at the bible yet, but I suppose the water temp sensor may be faulty.

[QBee]

If you are going to change it, then consider getting a different sender from either Caerbont or Caterham, and fitting it where the redundant Range Rover sender is on top of the engine, just in front of number 1 injector. Once fitted you just need the wire off the TVR one that is down the front of the engine. Same fitting.
The advantage is that it actually tells the truth. They cost about £15-20.

Go to this thread - ignore the first page and a half talking about variable resistors. Middle of page 2 is where you want to start.
The part number is TT 6811-03

https://www.pistonheads.com/gassing/topic.asp?h=0&...

Edited by QBee on Friday 7th May 09:55

Edited by QBee on Friday 24th June 11:11

[planes49]

Many thanks with that. I am having great trouble locating the lower one. I think there is a green wire running from the loom on the top one down into the bowels, but am nor quite double jointed enought to get in the bay and find it. This is despite all the helpful photos on the site! repacing it on top one looks more straightforward. I guess if I can establish that the green wire is the feed, I could just cut that and use it.

[Belle427]

Are you confusing the otter switch and the temp sender for the gauge?
The sender for the gauge is in the inlet manifold and should have 1 wire to it which is green/blue in colour.

Edited by Belle427 on Sunday 9th May 17:30

[planes49]

No problem identifying the otter switch. Shall try harder to find the temp sensor.

[Steve_D]

planes49 said:

No problem identifying the otter switch. Shall try harder to find the temp sensor.

If you stand at the left of the car and lean right over and look down the far side of the dizzy you should find it sticking out from the front of the inlet manifold in the engine valley. you will probably need some rather long needle nose pliers to remove the spade terminal.

Steve

[planes49]

Got it!! It is of course where it should be! In broad daylight and with a torch to help. It is underneath a wiring loom. Even managed to get the terminal off with a screwdriver. I suspect that if I could get down in there with some sandpaper that all would be well, but have just ordered a sensor up from Redline as recommended. Very helpful guy. I shall fit as recommmended in unused Rover port. Incidentally the green wire which runs down past the top sensor was the correct one. Many thanks for all the inputs everyone.

[QBee]

Top hole!
That's where the new sensor needs to go if you have bought the alternative one I suggested.
The TVR spot is in an aquatic cul-de-sac, which is why it doesn't read correctly.
Next to the ECU sender is the best place.