Ok guys so I need help trying to figure this out, I dont drive my vette eceryday because i work so far from home and i use a different car to travel to work. this weekend after i had let my car sit for the week i noticed that upon starting it had a rough idle at first then it started to smooth out, the ambient temp in AZ is probly around 50F so i dont think that could be it but what else am i missing. any ideas? or is this a normal situation after sitting. any help would be great...

 

My 1990 is doing the same thing for the same reasons. The Battery is only a year old. The alternator is several years old. If I start the car up the same day or a day later its ok, but if it sits for a while, I need to get the battery charger out and trickle charge it up. I know that the clock is small drain, as is the computer. If I use one of those battery shut off switches, then I will loose all my radio presets, and the computer will have to relearn how to run the car. At least that is what I have read about my engines computer. Anyone know of any other sources of drain on the battery?

 

Check the lights under the hood. I have heard of those staying on and draining the battery. I think some guys leave them unplugged for that very reason.

 

The security system will drain down the battery.
I think after 20 day's or something like that the car will shut down and stop the battery from draining.
I can't remember all the things that the electrical system does but it can be a pain.
That is why alot of new VW BUG owners got rid of their cars,after 30 day's you have to tow it to the dlr and have it restarted.

 

Thanks for the advice. I will unplug the underhood lights and see if that is making a difference. I started my car on Sunday after recharging the battery. Drove it around the block a few times and let it idle. Now on Wednesday, I had interior lights, but the starter would barely turn over. I need to recharge again. Maybe it is a dead cell in the battey???

 

Thanks redc4, my 86 has the same problem as the rest here, my under hood lights are unpluged and after a week it's almost no start, i never thought of the security system, i guess thats why a lot of owners use a battery tender.

 

Never had a clue when i bought mine that there was a issue with the battery, starting to see a sign of things to come, no wonder when i bought the car they were sure to tell me how to remove the battery
and here i thought he was just being nice.........

 

The 86 also at times has a problem with the a/c blower motor staying on low and running the battery down.
Even with the key off and out of the car.

 

Thanks again,.....how is it able to do that, and how can i correct it? Was this a common problem? Since reading this thread i have put a 6 amp charger on the car and it's taking longer to come back than my altered did to recharge after a race and it ran just off the battery. Thanks again. joe

 

You should be able to let your car sit for 1 week and be able to restart your car. I would measure the leakage current to see if it is normal. GM says leakage current shouldn't be larger than 50 milliamps. My 87 measures 27 ma. Remove the negative battery cable and connect an ammeter between the negative battery post and the battery cable. Start the ammeter out on several amps full scale because the courtesy lights will come on and you can damage an ammeter on 100 ma. full scale this way. After the courtesy lights time out you can switch your ammeter to lower full scale to measure the leakage current. It takes a long time to recharge a battery and you should never use your alternator for that job, use a battery charger. Car batteries self discharge up to 1% each day even disconnected and as they discharge, lead sulphate collects on their plates and lead sulphate is a good insulator. A fully sulphated battery is a door stop! Buy a battery tender to keep your battery charged when you leave the car sit. If you already have a battery charger, buy an interval timer (turns your home lights on each night when you aren't home) and have it charge your battery each day on its minimum interval (usually 15 mins), and even an hour won't hurt your battery. You can tell the state of charge in your battery by measuring the battery terminal voltage. 12.0 volts and below, discharged. 12.9 volts and above, fully charged and linear in between, example: 12.5 volts, 50% charged.