Speedometer fault, advice please, :scratchchin:

[peter miller]

My speedo on my 99 chimaera has after a recent spell in a damp garage started to give a few problems.
I noticed yesterday when driving, it is giving a very erratic reading below 30 mph, Above this speed it was ok, but gradually it was starting to get worse,until it finally died, unless above 40 mph. I should also note that when the speedo is playing up so is the odometer.
I jacked the car up this morning disconnected the first block connection and gave it a good clean along with the pick up area on the sensor.
Using feeler guages I measured the gap between the sensor and drive shaft wheel which was approx .o15" or just over 1/4 mm.
I then ran it in 2nd gear on raised idle, but problem was the same. so tried to reduce the gap further, but to no avail. Unfortunately I think I may have run it with the sensor touching the wheel as it now refuses to work at all. I have now removed the unit and before I start ordering parts would appreciate some advice.

1. could this problem be damp that might have affected the fuse box ?

2. Is it likely that I have blown a fuse or finished off the sensor when it came into contact ? and can it be bench tested ?

3. Is there any other possible cause for this fault ?

4. If it needs to be replaced, is this part TVR specific, or can it be sourced elsewhere, and how much can I expect to pay ?

Thanks for your help

>>> Edited by peter miller on Friday 7th May 18:41

[shpub]

Covered in the bible. Unless you have got a scope to look at the pulsetrain, very difficult to diagnose what/where the problem is. If it has been cleaned and the gap checked, then there is something badly wrong. Could be duff sensor but this rarely blows the fuse. If it didi it would take out other things a it is part of the ignition/instruments circuit.

TVR part and a sensor can cost between £65 to 150 depending on which one it is.

Steve
www.tvrbooks.co.uk

[peter miller]

Thanks Steve,
I checked all the fuses as well, and as you expected they were all ok, and nothing else has been effected, which would run off the same fuse, also it has had no effect on the running of the engine.
There is a number stamped onto the sensor at the hexagon end where the wire enters, ref - (180087) hopefully it can be identified by this.
I bought the 2nd edition bible when it first came out and its still next to my bed, I read it if I am having trouble getting to sleep, and it works every time...
Although I want to service and look after it myself, electrics are certainly my weak point so before I do any damage I think it best leave this to a professional

>> Edited by peter miller on Friday 7th May 18:41