Why does my car feel like it got a tune up when I charge the battery?
 

'74 CIS

I'm working thru my CIS issues and the car is running pretty good.

About every 6 weeks, the battery seems to get low on charge. I've had the alternator checked and I'm told it's fine. The only reason for checking is that the prior owner told me there is a slow drain (he only drove the car once monthly). I can tell when the battery is getting low because the car starts slight bucking at 2k-2.5k rpm

My first course of action was to get a new battery - 2 mths ago and check the alternator. Everything checked out good.

But, as I mentioned earlier I charge the battery about every 6 weeks or so and the charger indicated the battery was low. After the charge, the car runs fantastic and acts like I added 10hp - what's up with this?

Alternator drain, feeding a dead/dying battery? WAG.

When the batt is low the ignition gives you a weaker spark

It's a brand new Bosch battery and while the engine is running the system tests at about 14.7 volts.

I guess this must be the case. How I find the drain will be a challenge.

Also make sure that the cables that connect to the battery are A-OK. I had corroded contacts and an internally corroded groung cable causing weak battery syntoms on my 30 year old Landcruiser. After findig out I was amazed to find out what could happen to those cables under the insulation. After fixing the problems, cleaning battery contact posts and clamps, and replacing the ground cable weak battery symtoms disappeared.

This may be my next course of action. The ground strap looks pretty new but the positive is not so great. And, this reminds me of when I sprayed the starter during an engine clean) and the started wouldn't turn off. Looking things over and the cables at the starter look terrible.

do you drive the car everyday?
a car that sits for a week or two the clock will drain the batt down enough to give you the symptoms described.

if the fella checked your system and the reading was 14.7 then everything is fine.don't go messing with too much or you may cause another issue.

I pretty much drive every day but I do park it for about a week a month when I drive the 944. I'm thinking that I may have a drain somewhere and I'm pretty sure the positive battery cable could be replaced.

Depend on how long your driving for too.
daily driving should keep batt charged unless when your driving you have the big stereo + other things on.
big amps draw a lot.
if you have an alarm it and the clock will draw enough over a week.

with ign off an easy way to see if something is one is to pull one fuse out at a time .if it sparks when you put it back in then that circut is live. check to see if that circut is suppose to be on (like the clock would be with ign off)

When he checked and got 14.7 was that at the batt or the back of the car on the reg panel?

That was at the battery. Which is the correct method for testing? This was just a friend doing the testing with a multi-meter.

That's fine .

+1
check the ground from the alt to the engine (clean) and from tranny to body. clean both batt connections and the ground strap to the body.
take the car and have the system tested, not just the alt.
even though you have a drain, it should not effect it while you are driving, as ong as the charging sys and ignition are OK.

even though your voltage is good, high cable/connection resistance can reduce current.

to check for a drain, you can use either a test light or multimeter.
remove the cable to the neg side of the battery. connect the MM/teslight in series with the cable and battery. with everything off, the ligth should not be on. if it is, remove fuses one at a time until the light goes out.

Also, you should check the condition of the voltage regulator in the back panel.
The 74' has a regulator external to the alt.

A few years ago, my battery would slowly drain over time because it was not being charged properly. It was the regulator's fault.

I usually drive my car only every 5-6 days and so far, clock and radio stdby drain didn't affect the cranking ability.