Novak Conversions Jeep Wrangler TJ radiator

Dead battery or water got in somewhere?

Succentor

TJ Enthusiast
Original poster
Joined
Mar 27, 2021
Messages
433
Location
England
TJ doesn’t get driven a lot, so I keep the battery on a float charger. Battery is 9 years old, though.

Last week I took it out - no problems starting, all ran fine. Got it quite wet and muddy on farm tracks with standing puddles - at times I had to go fast enough that the water splashed up over the windscreen but it was never more than 3-4 inches deep. Parked it for an hour, started up fine.

I wasn’t going straight home so I took it to a gas station jet wash to get the worst of the mud off. Stopped for an hour, it started but was a bit reluctant to start. Parked it up, put the battery on charge.

2 days later, my son went to start it and the battery was dead. Odd, as the charger said the battery was fully charged. Put it on a different charger which showed weirdly fluctuating voltage levels like it couldn’t decide what voltage to charge it at.

Dead battery all of a sudden (it is old, I guess, but absolutely fine) or did the jet wash get water somewhere it shouldn’t? If it’s the latter, where do I look first?
 
Do you have a multimeter to check voltage with the key off, and when trying to crank the starter?
Looks like you have a 2001, so your distributor is also a candidate for no start when it gets some water. Check that that's nice and dried out
 
Cranks but just barely. ‘Whomp whoomp…' then nothing

Yes, I do have a multimeter - what am I looking for?
 
Ok, so the battery is clearly FUBAR.

Before cranking: 12.1V. Turn ignition on, 8V. Crank, 3V…

Hopefully that’s it and there isn’t anything else nasty going on. Booked anyway for a service and MOT (inspection) in early January so they will replace the battery at the same time.
 
Novak Conversions Jeep Wrangler TJ radiator