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?

 

Hi Crumble,
If I were you I would get the alternator checked/reconditioned or replaced before something expensive gets fried.

I would also check all the ground points around the car but from what you have described points to the alternator/voltage stabilisor breaking down.

Hope this helps.

 

Thanks jimbov8,
Just wanted to make sure before I take the car to the garage, hate the thought of the process where parts are replaced before the cause is found.

Saw an new alternator on Ebay for £100 ($150), is this risky?

 

Just to close this off, it did turn out to be the alternator.
I replaced it with a refurb unit and the car is running perfectly.

Thanks all.

 

Digging up an old thread,but...
I had exactly the same symptoms: pulsing lights, trac fail, stab fail, gearbox fault and code 1793 thrown when I started the old girl this morning. Today is going to be interesting!

It 'smelt' a bit alternatorish (is that a word?), but to find this post describing exactly the same issues made the diagnosis dead easy. Thanks, crumble



Not sure if it's coincidence, but the OP said his problems arose after a thermostat replacement. I accidentally left the bonnet open overnight - no rain, but there was a heavy dew this morning.

This forum is just amazing!

Thanks,
Mike