www.jec.org.uk

Hi.

I have the standard trip computer in my 89 XJS (5.3 HE), but it behaviour is quite erratic. some times the buttons work, others they do not. The screen sometimes goes blank or displays "88888" etc...

Is it likely the unit itself is at fault, or is it more likely some type of sensor issue?

I have had issues with the sensors before and what I noticed was that the basic functions still gave a reading (ie time, fuel used, consumption, distance etc) but the values given were rubbish.
It sounds to me like the actual computer has gone on the blink.
I can't see from your post where you are but I live near Salisbury. I have a spare computer and you're welcome to pop in here to try it out on your car if that would help.
Otherwise, there's usually some listed on eBay or try Graham at Grublogger. They can also usually be found at the Stoneleigh spares day but you've just missed that and the next one is in October!
I also know that Hollygrove in Ringwood have some (01425 477000)
Hope that helps!

Hi.

I have the standard trip computer in my 89 XJS (5.3 HE), but it behaviour is quite erratic. some times the buttons work, others they do not. The screen sometimes goes blank or displays "88888" etc...

Is it likely the unit itself is at fault, or is it more likely some type of sensor issue?

Given that it sometimes works, I'd guess at a dry joint inside or bad connection in one of the power/earth feeds. The old PC trick of unplugging and replugging everything in sight might fix it. For extra merit stars, spray the connections with Maplin contact cleaner and contact grease. A dry joint is much harder and might need a steady hand with a fine tipped soldering iron.