A Puzzling Car Problem

It could be the battery if it has been really hot.

"Even though battery capacity at high temperatures is higher, battery life is shortened. Battery capacity is reduced by 50% at -22 degrees F - but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures - for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever. This is actually not as bad as it seems, as the battery will tend to average out the good and bad times. Click on the small graph to see a full size chart of temperature vs capacity." source

 

aka, bad ground (corroded or loose) or main power relay.

 

Is this Discovery vehicle you speak of made by Volkswagen?

First thing to do: remove and re-tighten the battery connections. Also, clean off any corrosion on the terminals.

 

But on the VW, you would need to remove the battery, battery tray, and the ground connection underneath the battery tray -- because that's where it would corrode.

Of course it can happen on other vehicles also, or at one of a dozen other grounding points hidden around the vehicles -- causing all sorts of problems.

VW isn't alone, the more electronic crap you get with the vehicle, the more problems you seem to have.

Almost makes you beg for a car with manual seats, windows, locks, and an 8-track deck.

 

My point being, the battery is the easiest place to start. Corrosion occurs on the batt terminals as well.

And VWs have historically had many electrical problems. Consumer reports says so, and so do I, having had two Jettas and currently a New Beetle.

 

Is the remote for it working? Sometimes the remote to open it is also an immobiliser and if it's damaged the car won't start.

 

Not a feature I would like in my car.

A bad ground can cause some very weird symptoms, as will a very nearly dead battery.