Battery/Starting problem

88911coupe · 12-05-2020, 08:52 AM

Had a weird occurrence this morning but back story is I've been noticing the battery on my rarely driven '88 Carrera seemed to be losing power too quickly, I checked the draw and it was minimal but don't recall the #s. Been keeping it on a tender and car has started ok since on rare times its driven. However this morning I took it off the tender and it was around 12.9 or so. Tried to start it and it turned over couple times then no more...all accessories work, windows etc. but no engine turnover at all. I can hear a click under dash in start position, if that means anything. Battery then showed about 12.5 and I put the charger on "Car Start" mode...same thing no engine turnover. The battery is about 4 years old so could this just be the symptoms of an old battery? Can a battery appear fully charged and not have enough "juice" to turn engine over? Note that I installed a new high torque starter from our host 3-4 years ago after a crappy rebuilt Bosch failed. I recall setting up a starter switch bypass few years ago but can't for the life of me remember how that worked. Would that be something to explore in trouble shooting? Thanks

lsf911 · lsf911's Garage

Did you check the voltage level of the battery when you are trying to start the car? If the voltage level drops then it could be a dying battery.

88911coupe · 12:54 PM

Ok will check that, thanks! Stupid question...to test that I just put the meter on DC Volts and the leads on their respective posts and monitor voltage in ignition start position?

911obgyn · 911obgyn's Garage

And check your grounds, andconnections to the battery

Flat Six · Flat Six's Garage

Quote:

Originally Posted by 88911coupe

Ok will check that, thanks! Stupid question...to test that I just put the meter on DC Volts and the leads on their respective posts and monitor voltage in ignition start position?

Yes

Quote:

Originally Posted by 911obgyn

And check your grounds, andconnections to the battery

This too.

darrin · 12-06-2020, 06:47 AM

88911coupe - wondering whether trying to jumpstart from a known good battery might be a good next step. Unclear whether your charger has the power to independently crank over your starter/engine - If you car starts right up from a good battery/jumper cables, would seem your grounds/etc. are fine and your current battery's simply toast. If you have the same issues while trying to jumpstart, checking grounds would make sense. Another option would be to pull the battery and take it to a FLAPS (friendly local auto parts store) so they can perform a free load test.

As for potential drain, once you're back up and running, worth confirming that your driver's side dome light switch is working (i.e. your interior lights turn on when you open the driver's door) -- after the engine's shut down, our Carreras' power window circuit is designed to stay energized (and drawing a little power) until a door is opened. When door switches get dirty / fail, the power window circuit remains energized and will drain the battery in around a week.

steve911T · 12-06-2020, 06:48 AM

If any doubt, take the battery out and have it load tested. I had THREE Batteries on my boat go bad at once. All read 12.9 volts and 800 cranking amps between them (new). Load tested and found had 40 cranking amps between all three. I had kept them always on the 120V on board charger and was told that is what ate the batteries. They were all 4 years old also. You also might get an AGM battery if yours is bad. Good luck! Steve

88911coupe · 12-06-2020, 11:30 AM

Yes I’m suspicious of the battery and plan to take it to Pep boys, also I found the passenger side window switch has apparently broken or failed internally and already ordered replacement.

darrin · 12-06-2020, 11:40 AM

if you do need a new battery, 1) get an AGM battery, which will minimize boilover risk in an overcharge situation, and 2) consider the slightly smaller group 48/h6 battery (vs. the stock group 49/h7 battery -- the group 48/h6 battery will mount to another hole in the battery tray w/o modification.

88911coupe · 12-13-2020, 01:49 PM

Well took it to Pep Boys since it still had some warranty left. Failed test and they no longer carry Bosch and are in process of shutting down their parts sales going to service only. Limited selection to replace it but ended up with a Champion as it appears to be the only brand they sell now. Got home and car fired up perfectly even though tester showed 12.6 to 12.8.