Tacho problem

Tacho problem

Author
Discussion

bills1

Original Poster:

305 posts

277 months

Sunday 3rd March 2002
quotequote all
On my S1 the tacho revs up to 3000 rpm then drops back to 0. The engine keeps going ok. If I lift off the tacho leaps back to life when the revs have dropped back. Sometimes its at 3000 and other times it will work up to 4500.
I have tried replacing the ignition fuse and cleaning the contacts and this means the tacho will get to 4000 plus before dropping back. But after a few runs it will only go up to 3000.
The engine runs ok with no misfire and it starts ok.

Anyone else had this problem and any suggestions gratefully received.

Thanks in advance

Bill Marshall

Paceracing

729 posts

273 months

Sunday 3rd March 2002
quotequote all
My tacho is also a pain in the arse, for some strange reason the revs displayed increase by 200 - 300 rpm when I turn on the sidelights. The same sometimes occours when I turn on the heater! It's probably a TVR thing with poor earthing.
Other than that no suggestions since the tacho runs off the coil.

Dave_H

996 posts

290 months

Sunday 3rd March 2002
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This has to be electrical, as Paceracing said, the tacho does get it's feed from the coil, I've had a simular fault with my MG years ago that ended up being a break in the loom from the feed from the coil.

I've not yet tried to get to this yet on my S, so not sure how easy, but if it were me I'd want to look at the state of the connection at the back of the tacho, and use a multimeter to check the connectivity back to the coil - might be a good idea to refer to the S Bibles wiring diagram to aid you with this.

Maybe someone else on here has removed the dash/got to the tacho, and can give clues/tips on how to do so?

Cheers,

Dave.

Dave_H

996 posts

290 months

Sunday 3rd March 2002
quotequote all
quote:

My tacho is also a pain in the arse, for some strange reason the revs displayed increase by 200 - 300 rpm when I turn on the sidelights. The same sometimes occours when I turn on the heater! It's probably a TVR thing with poor earthing.
Other than that no suggestions since the tacho runs off the coil.



Mine does the same. I think the official TVR answer is "They all do that Sir"

bills1

Original Poster:

305 posts

277 months

Wednesday 20th March 2002
quotequote all
Success.
After reading the bible again it pointed out how the dreaded rain gets in AND especially when you wash it and give it a glorious rinse with hose especially down the windscreen.

When I fecthed it out the garage and went for a blast no problem. I then washed an cleaned it and back came the trouble which a good spray with WD40 has cleared.
I have since sprayed it with sealant after finding no obvious weaknesses in the wiring above the fuse box and near the coil.
From now on when rinsing off I will never hose down the windscreen because as the bible informs the water is run straight over the coil.
(Dont tell me you all knew this and it was obvious, I am not feeling very clever)

I have yet to be out in heavy rain, if the fault reoccurs the some rewiring is no doubt needed

tvradict

3,829 posts

281 months

Wednesday 20th March 2002
quotequote all
quote:

...as the bible informs the water is run straight over the coil.




sounds a bit dodgy to me?!?!?! A bit TVR'ish!

mhibbins

14,055 posts

286 months

Wednesday 20th March 2002
quotequote all
quote:

quote:

...as the bible informs the water is run straight over the coil.




sounds a bit dodgy to me?!?!?! A bit TVR'ish!

Keeps it clean

tvradict

3,829 posts

281 months

Wednesday 20th March 2002
quotequote all
quote:

Keeps it clean