Supercharging the climate with a XJR V8 - MOT Passed

[Hooli]

Another update, google is talking to me today.

Most answers I'm finding suggest the brake light switch, as it's linked to the cruise control it triggers an engine warning if it's not giving a clean signal. This rings a faint bell from the specialist mentioning a brake light code but it tested ok.

It seems a test for this is to drive around without the cruise control switch on, if the fault doesn't appear then it's very likely to be the brake light switch. I always leave the cruise turned on, so it makes sense it could be that.

Guess I should see if the brake lights work too?

[richardthestag]

Very short update.

No forums appear to have any idea of the fault, their so called technical knowledge sections mostly consist of 'this specialist in your area is best'.

I had this shit with the abs fault etc on the 4 litre sov that you bought from me.

Eventually got to the bottom of it being a battery that was operating at less than 12.8v standing.

It's progress donchano

[AutoshiteBoy]

Best of luck with this fault.

[Hooli]

Guess I should see if the brake lights work too?

They do, which annoyingly doesn't mean the switch works properly for cruise.

[Hooli]

Very short update.

No forums appear to have any idea of the fault, their so called technical knowledge sections mostly consist of 'this specialist in your area is best'.

I had this shit with the abs fault etc on the 4 litre sov that you bought from me.

Eventually got to the bottom of it being a battery that was operating at less than 12.8v standing.

It's progress donchano

Yeah I saw that occasionally on that car too. I'd swear it had a weak alternator as I could provoke that issue by using the heated window, fan etc etc plus lights on the trip to work a few times. Under the same conditions the XJR doesn't complain at all and I'd be using the heated seat too (which didn't work on the Sov if you remember).

[richardthestag]

Very short update.

No forums appear to have any idea of the fault, their so called technical knowledge sections mostly consist of 'this specialist in your area is best'.

I had this shit with the abs fault etc on the 4 litre sov that you bought from me.

Eventually got to the bottom of it being a battery that was operating at less than 12.8v standing.

It's progress donchano

Yeah I saw that occasionally on that car too. I'd swear it had a weak alternator as I could provoke that issue by using the heated window, fan etc etc plus lights on the trip to work a few times. Under the same conditions the XJR doesn't complain at all and I'd be using the heated seat too (which didn't work on the Sov if you remember).

farts helped to warm the leather

[xtriple]

Brake light switches failing is a 'thing' nowadays. Never used to be did it... in my day things were much bettererer. Mercs do it all the time and give a dash full of warning lights and the lights still work. So I vote to change the switch, if it's owt like a Merc it is the easiest thing in the world to do short of fall over.

[Hooli]

Free updatings, more updatings than previous updatings....

Leaving the cruise control turned off results in no warning messages, which pretty much proves it's the brake light switch. I'll have a look at the switch this weekend & if it looks like it'll come apart I'll get it out & try, if not I'll order one.

Just the damned wobbly seat back to fix after that before it'll drive right.

Talking of driving right, it got a spirited drive back from work this evening on nice empty roads. Damn it's rather pointy & quick on bends now the front end isn't made of several bits of metal not talking to each other. I thought it handled well for a small oil tanker before, but now it's quite indecent how it behaves. It lives up to the hype from 20 years ago when I first wanted one.

[Hooli]

Brakelight switches are £100! bloody crazy as it's just two microswitches in a plastic box. I've got a second hand one on the way for £45 instead.

Once the old one is off I'll see if I can source the same size microswitches to fix it & put it on the shelf as a spare.

I found a genuine Jag tech bulletin about it tonight too, how exciting!

[AutoshiteBoy]

I maybe telling you how to suck eggs, but is there not a website which cross references parts from Jags which may also appear in Fords or BL Ambassadors and the like? SAAB moaners had a similar set-up to good effect.