Intermittent speedo

[monty quick]

My speedo (needle and digital) sometimes drops to zero and sometimes bounces around from zero to the correct speed and, most of the time, works normally. When it is having a crazy moment I am sure I can hear a buzzing which is not there when everything is OK?
I reported this fault when I bought the car 2years ago but Fernhurst couldn't find a problem. It is now getting worse.
Do any of you clever folk have any ideas?

[shep1001]

monty quick said:

My speedo (needle and digital) sometimes drops to zero and sometimes bounces around from zero to the correct speed and, most of the time, works normally. When it is having a crazy moment I am sure I can hear a buzzing which is not there when everything is OK?
I reported this fault when I bought the car 2years ago but Fernhurst couldn't find a problem. It is now getting worse.
Do any of you clever folk have any ideas?

If they both do it (analogue & digital) I would say the speedo transducer mounted on the diff is on the fritz or if you are lucky just needs a clean/adjustment.


Shep

[NCC]

shep1001 said:

If they both do it (analogue & digital) I would say the speedo transducer mounted on the diff is on the fritz or if you are lucky just needs a clean/adjustment.


Shep

+1

Had the same thing with the Tamora when I first got it and was suffering the 0-60 in 0.01 seconds thing in the T350 until recently. New transducer fixed the Tam 8 years ago and the T350 last week

[monty quick]

Thank you clever people. I will have a look this weekend.

[chris watton]

shep1001 said:

If they both do it (analogue & digital) I would say the speedo transducer mounted on the diff is on the fritz or if you are lucky just needs a clean/adjustment.


Shep

I told Adrian at Central TVR to look at this for me, and he said it is usually what you mention above - hoping that is the case. Mine worked flawlessly on the way to Stourbridge though!

[TVRobsessive]

My T350t had the same problem. Sometime the speedo worked faultlessly, sometimes intermittently, then it stopped working for a couple of days. I adjusted the sensor, but no difference, so ordered one of the new uprated sensors from RG. Fitted it with the new bracket, but unable to pull the connecting cable because my sensor loom disappears into a length of cottugated tubing which is heavily sealed & goes round a few corners before emerging over the top of the tank & into the n/s rear sill space. So I just spliced it into the existing wiring under the car. Guess what : speedo still not working. Started getting slightly frustrated by this point. Next day, with help from better half, I metered the loom cables out , her in the boot & me under the car & discovered the signal cable had a break in it somewhere. How? One of life's little mysteries. Anyway, I managed to get a single cable through from the boot to the sensor to replace the broken one, soldered & waterproofed all connections & speedo works perfectly once again. This is another of those 3 hour jobs that takes 2 days! Moral of the story : check the continuity of the sensor cables before you spend £ 100 on a new sensor. Incidentally, on the T350, you can get the sensor loom out by pushing your arm into the n/s wing space (after removing the trim) as far as you can. You'll feel a bunch of cables : find the narrow one, which consists of 3 cables bound together & gently pull into the boot. There should be a 3 pin connector on it. Hope this helps.