Hi All,

I need a little help tracking down a problem with my 1998 XK8.

I recently had the thermostat replaced by a local garage. The car ran fine for a day then the "gearbox failure" lit up and the gearbox stayed in one gear. I nursed the car home (2 miles) and restarted the car on my driveway. The messages had cleared but the engine was pulsing, rising and falling revs like a sine wave, quite fast perhaps twice per second. All the interior and dash lights were pulsing, if I reved higher the pulsing remained. Took the car out for a spin and after 5 mins I heard a light clunk and "gearbox failure", "ABS Failure" "traction control Failure" messages appeared. Nursed the car back again restarted the car and all was clear again (except for pulsing). Tried again, clunk, got the messages and the voltage dial went to max.

Attached a cheap OBDII reader and got P1793. A search on the web points to gearbox sensor or voltage out of range.
I checked the battery after it had been standing for a few days and got 12.35 volts and with the car running at idle 13.7 volts. It did shoot up to 16.5v and I switched the car of at that point.

I mentioned the thermostat replacement as it is in close proximity to alternator and maybe a wire was dislodged.
Am i right in thinking that the alternator regulator could be at fault and if so can I test for this and replace it without replacing the alternator?

 

You would probably get more help in the other XK forum...this area is for the X150 cars...

However you are correct in that you can get the alternator checked. I don't know what's available where you are but here in the US we have auto parts stores that will check your electrical system for free. They have portable machines which can test your alternator, battery, and other items within your electrical system.

Good luck!

 

Thanks for that. Didn't notice the other forum. I will repost over there and hope there is a way to delete this one.

 

Yeah, that jump up to 16vdc shows signs of the alternator regulator being kaput or if the regualator is inside the ECU.....uggggh! Too lazy here to see where the regulator is on this car.