Is there any harm in leaving the cruise control switch on all the time? I've had cars in the past with a vacuum fed system which always seemed a bit precarious. But the switch on the Jag is easy to forget to turn off and if it's popped up it's always ready.. is that a bad thing?

 

I'd like to know this too, I've kept the habit since the 2000's on any car around this age to do the following after stopping/before parking: set park brake, put gear in park (or 2nd on manuals) turn off A/C, turn off cruise control, turn off radio, turn off any other electronics running (like sport mode) before shutdown. Why you might ask (because my wife sure thinks it's excessive)? In aviation, airplanes/helicopters require a similar shut down process to avoid burning up or "glitching" the sensitive electronics that are based on the most advanced technology available around the 1980's, technology that made its way into the auto industry over time regarding these chips and "computers" that run our cars. Makes sense to me to shut everything down so when you start the engine again, nothing is affected by the unsteady power delivered while turning the starter to power the car.

That being said.. Does my wife do this with her 2015 VW passat? Never and everything still works fine at 120k miles. Do I do this to the 2020 company car that takes a daily beating where I'm in and out of it multiple times a day? I could care less. But something about the older cars I own urge me to take more caution. I once worked at an Audi dealership and have seen more than one 2005-10 year range Audi for sale on the lot have a complete failure of the infotainment/climate cluster in the dash and always wondered if it could have been related to sales never turning anything off after test drives. But newer Land Rovers and other cars also now have glass gauge clusters that can not be turned off at shutdown. And interestingly, I have known several Land Rover gauge displays to stop working as well, could be heat/cold related but who knows?

 

Guys, its an ignition switched circuit, so no drain with key off. There's no reason you can't leave switch "on" 7 x 24. You're ok.

Funny thing I remember though. A sentence in the owner manual as constructed sounded like acceleration is maximized with Trac Off and cruise control Off. True with Trac off since software intentionally reduces engine's power output with any sign of wheel slippage. The
cruise control part, I'm sure, is just one of my hyper analytical interpretation of a simple sentence.

Though, true be told (laughing at myself), after reading that I jumped in the car to "test" it out. Oh yes, that damm placebo effect got in the way (again) :-) she felt faster.

John

 

My 06 cruise control is always on. Pushing the button puts it in speed limiting mode, otherwise I just have to touch the steering wheel buttons to set it. The AJ26 has the vacuum switch on the throttle body, but I don't see where that would make a difference.

 

D, regarding RJ'S comment, file this one away:

Like he said our cc is vacuum regulated. I have a 98 too. Once I was driving cc on, all of a sudden I lost cc, even the button's light went off. The scary part was the message on the display, I forget the exact wording but it was something like critical failure failsafe mode!

Good news was, a simple ignition on / off cycle and all was ok - until i put cc on and the road went uphill - same problem! Turned out that the vacuum hose came off the throttle body. When the car went uphill, of course it slowed so cc sent vacuum to throttle body to increase throttle. With the hose disconnected, it was an open loop vacuum leak, no speed change = car thinks something is VERY wrong!

Just a matter of reconnecting the hose, all ok. Why did hose fall off for me? Turned out the engine mount was gone on 1 side. Throttle resulted in lots of engine movements, pulled the hose off. BTW hindsight: the fact that the silencer attachment to the air filter housing kept "wiggling off was an early indicator.

We see this disconnected vacuum hose once or twice a year, but you're new and the last thing you need is that message on a trip 100 miles away from home :-).

John

 

May be a reference to the cc 'resume' feature that doesn't use maximum acceleration, to avoid any nasty surprises and to save fuel.

/Simon