My XJ8 battery goes completely flay if car isn't driven for 5 days or so. Anybody got any words of wisdom?

 

Check the ignition barrel flap is closing when you remove the key.
Turn of all auto functions when you lock the car up.
If that fails then disconnect the alarm chirp sounder (behind the right front wheel liner) this is a known problem for battery draining as the internal battery corrodes over time and shorts out.

Hope this helps.

Jim

 

These cars need to be kept on a battery maintainer when left to sit. I had the same problem until I purchased a NOCO Genius G1100, now it stays @ 100% regardless of how long it sits.

 

Cheers Jim. I've got my fingers crossed it is going to be the ignition barrel flap.

 

Both of mine can sit for weeks ...

 

Every one I've encountered 4-5 days was the magic # lol. My associate was just ranting Friday about having to call AAA for his. Mine's definitely not the ignition barrel flap as I've checked that.

 

Hi King Charles,
Solid advice but unfortunately I have no garage and have to park my car on the street.

 

My battery would go flat, maybe 5 days, maybe 8 or 9, the unpredictability made it even more maddening, turned out after many other checks (& balances?) to be my glove box door. If I was parked facing uphill, the weight of the door made it sag open just enough to trigger the light. Since my parking place was somewhat variable, so was the problem until I happened to reach in the glove box for something and felt the heat from the lens of the light when it should have been cold.

 

Mine can also sit for weeks and start without problem.

I went through the electrical system quite some time ago
to ensure that all power distribution contact points were
clean. Including the alternator bracket to engine block
interface.

 

Thanks I'll check the glove box aswell.

 

Well now it looks like a multi-meter & a proper whisky are in order to sort out this parasite. My neighbors love seeing me in a-shirt,boxers w/ a tactical light in my mouth sorting out my cars @ 2 am lol.

 

Double check all the lights that come on with a mercury-type switch (door to glove box; center box; trunk). Barring that run an ammeter across each of the main fuses to see which are drawing power while the ignition is off. Then check each individual circuit fed by the hot one.

Favorite story: years ago, I had a 1973 Bavaria in Yokohama Japan that was eating batteries ever third day. Was about to pull the wiring harness, when a young Navy Chief who worked in our office told how he found the problem while working for a BMW dealer in Germany: "its the button for the trunk light!" So, I stick my 4 year old son in the boot and tell him not to panic when the light goes out but to knock hard and I would let him out. Not hearing anything, I open up: "Why didn't you knock?" "The light didn't go out, Daddy." The spring loaded button had dug a hole in the plastic trunk liner: quick fix, a 25 yen piece, and duct tape to hold it over the indentation.