I am wanting to make sure I am not chasing rabbits that aren't there. I have a relatively new battery purchased around March 2021 with a cold cranking amps of 800. It is a WalMart battery. Recently during this cold weather the car sat a week and when I went to start the car, the engine would not turn over; it did do the clicking thing. I charged the battery and the car started. I did not do any tests of the alternator. Due to winter storms, the car again sat for several days. I went to start the car again and once more, it would not turn over, doing the clicking thing. I charged the battery and then started the car. The alternator was charging at 14.9v dropping to 14.7 and then 14.3 over a period of time. The next day I checked the battery voltage with the battery connected to the system and it read 12.5 volts. The car started with no problems. I decided to check the standby current draw of the system. When first connecting the amp meter I get a draw of O.74 amps dropping to 0.14 amps once relays and modules have gone into the standby state. I have tried searching the net for the standby current drain but was unable to find anything conclusive. Perhaps everything is OK here and I just need to make sure the car does not sit so long. Back in December before the storms and the long periods of cold days and nights, I drove the car once a week. During January, the car has been sitting for extended periods and the weather has been cold and winter storms has prevented me driving the car.

I am going to give an update. I remembered that I had horn issues with the horn wanting to start blowing on its own. I unplugged the horns but it occurred to me that the horn relay may be energised. I located the horn relay and removed it but didn't see any change in the current readings of O.74 amps dropping to 0.14 amps. I decided to pull the horn relay fuse (which is horn/door locks/trunk release) in that maybe there is an issue with the circuit and not the horn switches in the steering wheel. I did the current draw test again and got the O.74 amps initially dropping this time to 0.0 amps on a 20 amp scale on my multimeter. I did not switch to a milliamp scale but just seeing that difference on the 20 amp scale has me wondering if there is an issue with the horn relay circuit.

140 ma is to much. Check on ma scale.

I likely have your answers:

1. Battery endurance in winter. I have a 1997 LeSabre (basically the same car). It can sit for long periods in winter with no issue, then start up as if I had just driven it the day before. My temperatures for this are well below zero degrees in the rockies, South Dakota, Wyoming, and Nebraska through well above 100 degrees (Fahrenheit) in the Mojave desert, Nevada, Utah, and Texas. I've always used Walmart batteries in this car, and they always last around five years. I've owned the car for just short of 20 years and over 160,000 miles.

2. Horn. This is likely caused by the airbag cover getting tight when it'* cold and everything contracts. This has it push one (or both) of the contacts that live between the air bag and the outer cover that you pound on to sound the horn. This was a common problem for many years with this design of airbag/horn hub assembly. The Roadmaster shared this design and also had the same issue. Both my 1997 LeSabre and my 1995 Roadmaster had the issue. These days the issues have seemed to go away, probably because most of them have been scrapped. On my cars, I ran around with no horn (pulled the relay) on the Roadmaster for a few years, and on the LeSabre I disconnected the horn wires many nights when I knew the interior would get super and duper cold. I hooked both of them back up a few years ago and have never had a problem since then. I suspect the plastic/pleather/rubber/etc./whatever material that they use for this gets less ambitious over time and/or heat cycles, and doesn't pull as tight on the contacts in the cold. One day I came home on a really cold day to hear this crazy sound I'd never heard before coming from the Roadmaster, which had been parked for a couple of days. It sounded to me like a large squirrel had gotten something caught in one of the fenders and was desperately trying to get out. Like very desperately but very random, but also weird. I cautiously opened the hood and couldn't find anything, but the noise kept going and sounded like it was alternately in one or both front fenders. A month earlier, a neighbor had mentioned hearing somebody'* horn blowing for hours on a cold day, but didn't know where it was. I didn't either because I was at work. Now here I am with two space squirrels using tritanium-dipped claws to try to get out of both of my front fenders and I realize one note of the horn is in each fender. Doh! Open the driver door and pound on the horn pad a few times and the sound stops. Pound on it again and can kind of make the space squirrels come back in bits. Guess whose horn the neighbor heard a month ago. That time it stopped on its own. This time it ran the battery down to 0.8 volts and that'* why the horns sounded so weird.

You'll probably notice that your horn is very sensitive when you do want to use it, like lightly brushing the pad will sound it. If that'* the case I bet your issue is the same as mine was. I thought of taking the pad off very carefully and creating some clearance on the inside of the pad so it wouldn't touch the contacts quite as hard, but never got around to it before time appears to have fixed it for me (knock on wood).

How much should the battery voltage drop sitting disconnected? I tested the voltage after allowing the alternator to fully charge the battery had had 12.6 volts. After sitting for 18 hours I have a reading of 12.4 volts. Is this normal for a lead-acid battery? I want to make sure the battery is good as well; if not then I will replace the battery as well as looking for what is causing the heavy drain.

Until you get a good battery you will be doing this........."I am wanting to make sure I am not chasing rabbits that aren't there.'

12.4V is fine. If it keeps going down along the same trend line (0.2v per 18 hours) while disconnected then that'* bad. I can't see a reason to replace the 10 month old battery.

It'* no guarantee with time. If it'* shorted internally which, can happen for many reasons, we need to see what it drops to in 48 hours.