Fully Charged, But No Start and Very Dim Trunk Light

[michaelm101]

This a re: a stored vehicle (1979 911 SCT) that gets started & driven every 3-6 mos. Garage kept and trickle / float charger on the battery with disconnect switch that is switched "OFF" during storage..

Today, I tried to start and nobody's home. Put the charger on and it tells me the battery's fully charged. However, the trunk light is VERY dim, and then it even turned off...

Can anyone tell me what's going on? Thanks in advance!

[7783911]

bad ground...check you main ground points especially at the tranny

[timmy2]

Or corroded positive post/terminals

[walt]

How old is the battery. I've seen old batteries show a full charge that wouldn't turn the starter over.

[michaelm101]

Originally Posted by walt

How old is the battery. I've seen old batteries show a full charge that wouldn't turn the starter over.

Battery is about 3-4 yrs old. Been on the trickle charger while in storage. Terminals are very clean. This is a mint condition vehicle. Recent photo below:

[darrin]

pretty car!

Have you tried jumpstarting it? Seems if it fires right up/and trunk light gets bright, it would be pretty clear that the battery's shot -- a dead battery could show proper voltage (float on the charger) but lack any real amperage/capacity to run the car. If jumping starts the car, I'd take the battery to a FLAPS (friendly local auto parts store) for a load test and, if dead, replace with an AGM-type battery

[michaelm101]

Originally Posted by darrin

pretty car!

Have you tried jumpstarting it? Seems if it fires right up/and trunk light gets bright, it would be pretty clear that the battery's shot -- a dead battery could show proper voltage (float on the charger) but lack any real amperage/capacity to run the car. If jumping starts the car, I'd take the battery to a FLAPS (friendly local auto parts store) for a load test and, if dead, replace with an AGM-type battery

Thanks. Will do- I'll use the "start" function on the charger as I'm not able to get another vehicle near it...

[walt]

Agree with above. Load test the battery at 3-4 years old.

[NYNick]

Put a voltmeter on the battery and see what you get. Then work your way forward.

[boyt911sc]

Have the battery tested and analyzed using a battery tester. A fully charged battery with 12-volt reading is only half of the equation. If the CCA (cold cranking amperage) is low, it would fail miserably cranking a starter. Bring the battery to your local auto parts store for free battery diagnostic test.


Tony

[Driven97]

If it's been working fine with this process for years and suddenly isn't, I'd definitely suspect battery first. Perhaps the float charger failed and overcharged the battery, killing it. Maybe just battery age.

Also could be sketchy disconnect switch, I have the screw in type, and I overtorqued it once. Every once in a while it doesn't connect quite right and I get a similar symptom - frunk light will light up, but go to start and nothing. I have a new one but keep forgetting to install it.

[spoke]

Originally Posted by NYNick

Put a voltmeter on the battery and see what you get. Then work your way forward.

I agree.

Put the headlights on then measure the battery voltage. Always do easy tests before doing harder things like removing the battery.

[lateapex911]

Check volts at the switch and jiggle...some of those switches are known flakes.