Gearbox fault - gets stuck in 1st gear - Rain Sensor ?

[svk123]

Hi,
I have an intermittent fault with the gearbox on my 1998 XK8 convertible (which have owned for around 20 years!)
Sometimes it shows "Gearbox Fault" and will not change up from 1st gear. After several attempts, the fault will clear when I turn the engione off then restart.
I have taken the car to a reputable gearbox specialist, BK Transmissions in Overton, who succesfully cured a different fault some years ago. Bill has diagnosed the problem as a faulty "Rain Sensor" but he says that a reaplacement is not available from Jaguar or from ZF. I am reluctant to pay £200+ for a second-hand one on Ebay.
I have no idea what a 'rain sensor' is but does anyone know where I can get a new or reliable replacement.
Many thanks,
SVK

[mike020150]

Hmm, is it possible that the diagnosis has lost in translation? Could your mechanic have said something like, 'range sensor'? To have confidence in providing advice for this type of problem, it would be helpful to have the diagnostic trouble code(s) that will have been stored within the car. Do you have it/them or could you get them from the mechanic? Also, when was the gearbox oil level last changed and checked? The checking process is not straightforward. If not done within a precise temperature range, the level can easily be set incorrectly (too low) which can result in the gearbox misbehaving. Mike.

[svk123]

Hi Mike,
Thanks for your very helpful reply.
I think you may be correct so it could be Range Sensor (not Rain Sensor !!) - also known as a Rotary Switch ?
I will check with Bill at BK and try to get more accurate details.
Many thanks,
Stuart

[andypryce]

The rotary switch on the side of the gearbox is a fairly common failing, used ones are not too expensive.

[andypryce]

One further thought, normally with the 'gearbox fault' message the car sticks in 3rd gear, so if it is definitely stuck in 1st gear then perhaps it is something else?

quick search has brought up a rotary switch on ebay:

https://www.ebay.co.uk/itm/176596207715 ... ENEALw_wcB

[svk123]

Many thanks to Andy and Mike for your helpful replies.

I am pleased to report that the problem has been fixed so this story has a happy ending. I can now describe the problem and the solution as this may help others with a similar problem.

The problem was that, when starting from cold, my XK8 would stick in first gear and not change up. It was an intermittent fault and could eventually be fixed by stopping, turning the engine off and restarting. There was also sometimes a clunk when changing into reverse. The 'Gearbox Fault' light came on sometimes.

I took the car to Bill at BK transmissions in Overton. Bill is a real wizard and knows everything about transmissions. He identified the fault code as P0706 and said it was the Range Sensor (also known as a Rotary Switch). I mistakenly thought he said Rain Sensor !!
Bill found out that neither Jaguar, nor ZF, still manufacture these so I had to buy a secondhand one online. Rather than buy on Ebay, I found one at Auto Reserve Jaguar who do at least offer a limited guarantee - cost around £200. The part was delivered the next day, fitted by Bill and problem solved !

Bill found that the problem was not actually the Range Sensor itself but was a broken wire in the cable - see photos attached. If I can get the wire repaired, I will now have a spare.

MOT and service next week. I hope it passes !!

[Thixendale]

That's great news and thanks for posting the solution.

Might be useful to have a spare.

Enjoy the car.

Tony

[andypryce]

Good result, you could always sell the spare once repaired and at least get something back!

[svk123]

Hi Andy,
Yes, I thought about selling it but, as the replacement was second hand, I don't know how long it will last. If the replacement packs up, I would then need to spend another £200+ so I think I will keep my old one as a spare. Plus I know it fits !!
Thanks for your help,
Best,
Stuart