Battery or Alternator?

[ArnieJr]

I'm a total newb on electrical things.

A few weeks ago, the 300 wouldn't start (1969 300, 440 K motor). Didn;t leave anything on or open, just turned the key and got two slow turns and that was it.

The battery's about four years old, I haven't driven the car but maybe 5,000 miles since I got it; once a week to work and toolin' around on weekends.

So I did a little research. They say the battery's supposed to show about 14 volts when the engine is running. But that's on new cars. Not much out there on the older ones.

I got my voltmeter out and checked my Honda. It's about 14.5.

The Chrysler battery was showing 12.06. I hooked the cables up (humbling, my little Honda starting the Chrysler) and it bumped up to about 13.2. Took several minutes and finally got the car started. After it ran for a little while, the battery was at 12.7. I shut it off, battery was at about 12.4. I let it sit for a few minutes, turned the key and it fired right up. Then it started to rain (no garage), so I couldn't test it any further.

So in short, based on that, is it a battery or alternator?

Also, are rebuilt alternators any good? They seem a little less pricey, but I don't wanna buy junk either, just something that keeps my battery charged.

 

[Ripinator]

I'm a total newb on electrical things.

A few weeks ago, the 300 wouldn't start (1969 300, 440 K motor). Didn;t leave anything on or open, just turned the key and got two slow turns and that was it.

The battery's about four years old, I haven't driven the car but maybe 5,000 miles since I got it; once a week to work and toolin' around on weekends.

So I did a little research. They say the battery's supposed to show about 14 volts when the engine is running. But that's on new cars. Not much out there on the older ones.

I got my voltmeter out and checked my Honda. It's about 14.5.

The Chrysler battery was showing 12.06. I hooked the cables up (humbling, my little Honda starting the Chrysler) and it bumped up to about 13.2. Took several minutes and finally got the car started. After it ran for a little while, the battery was at 12.7. I shut it off, battery was at about 12.4. I let it sit for a few minutes, turned the key and it fired right up. Then it started to rain (no garage), so I couldn't test it any further.

So in short, based on that, is it a battery or alternator?

Also, are rebuilt alternators any good? They seem a little less pricey, but I don't wanna buy junk either, just something that keeps my battery charged.

I think you just need to charge the battery. If you are not going to drive the car much, get a smart charger and leave it hooked up all the time. Of course, your battery is four years old or older, so you may really need a new one.

 

[CBODY67]

The old points-style voltage regulators were supposed to be set for 13.2volts when running, with the ambient air around the regulator at 80 degrees F or so.

Unless you want to buy a battery, get a battery charger and fully charge the battery. If you need to remove it and take it inside (or on the back porch), do that. Clean all of the battery ends and battery terminal posts, too. THEN see how things go. If the battery stays "up", save your money.

Most of the newer cars' electronics are designed about a battery voltage of 14.2-15.0 volts, by observation.

Enjoy!
CBODY67

 

[Ross Wooldridge]

Firstly, get a decent battery charger and charge your battery on the lowest charge rate for a couple of days. That will maximize the battery's charge uptake. Do a load test on the battery to see if it stands up. If it fails, replace the battery.

If it passes, recharge the battery again - a few hours should do it. Reinstall the battery in the car, and start the car.

When you start the car, watch the amp gauge - it should show a considerable + on the needle for the first 15 - 30 seconds or so after starting, and then settle back down to just above center if the battery is good, or stay strongly in positive territory if the battery needs charging and gradually settle back (which it shouldn't if the battery is good). If not, the alternator may not be not charging.

If your alternator is charging, it will magnetize the bearing. With the car running, put on the heater fan and the headlights, then hold a screw driver tip to the center of the bearing on the back of the alternator (be careful of belts etc...). If you feel a magnetic pull, the alternator is working.

Long periods of non-use kills batteries. So, I keep my batteries on a trickle charger all the time - I have a battery in my garage that's 15 years old and still passes the load test, and the one in my car is 7 years old I think.

Whenever I park the car, I just hook it up. Always starts the car well, and doesn't wear out the alternator as quickly.

 

[HOT FURY]

or add a battery quick disconnect to the negative terminal and "unplug" if not in use for long periods to keep it from slowly draining

 

[Ross Wooldridge]

Again, leaving the battery not charged like that is not the best practice in my experience, so I put the maintenance charger on it while disconnecting it from the car at the same time... I do this with all my car batteries.

The challenge for me is that I like my clock to not have to be reset every time I drive the car, so I have to leave it hooked up which subjects the battery to a slow drain, so the maintainer helps deal with that.

For safety and security reasons I would prefer NOT to have the battery hooked up - in case someone were to try and start the car and drive it away, and as well, to protect the car if for some silly reason there's a bad short to ground... so it's not fully hooked up. Instead, I use one of those quick disconnect thingies with the green twist knob on the negative post and disconnect the battery that way every time I park the car, but I also run a 12 AWG wire between the negative post and the negative battery cable with a 3 amp fuse in it. That allows the clock to run (and the dome lights to come on if I open the car door) but anything with a stronger draw than that will blow the fuse.

 

[Boydsdodge]

Again, leaving the battery not charged like that is not the best practice in my experience, so I put the maintenance charger on it while disconnecting it from the car at the same time... I do this with all my car batteries.

The challenge for me is that I like my clock to not have to be reset every time I drive the car, so I have to leave it hooked up which subjects the battery to a slow drain, so the maintainer helps deal with that.

For safety and security reasons I would prefer NOT to have the battery hooked up - in case someone were to try and start the car and drive it away, and as well, to protect the car if for some silly reason there's a bad short to ground... so it's not fully hooked up. Instead, I use one of those quick disconnect thingies with the green twist knob on the negative post and disconnect the battery that way every time I park the car, but I also run a 12 AWG wire between the negative post and the negative battery cable with a 3 amp fuse in it. That allows the clock to run (and the dome lights to come on if I open the car door) but anything with a stronger draw than that will blow the fuse.

I like that, I leave my Imperial connected with a battery tender. I don't want to mess with the clock after a long park, the clock holds fantastic time at 1 minute a month now and I don't want to mess that up. Your light wire with fuss is a great idea.

 

[3175375]

I like that, I leave my Imperial connected with a battery tender. I don't want to mess with the clock after a long park, the clock holds fantastic time at 1 minute a month now and I don't want to mess that up. Your light wire with fuss is a great idea.

The only clock changes that you have to make are for daylight saving time and not.

 

[Boydsdodge]

The only clock changes that you have to make are for daylight saving time and not.

But if I leave my battery unattended, I will be setting it as the battery drains and clock stops or slows.

 

[3175375]

But if I leave my battery unattended, I will be setting it as the battery drains and clock stops or slows.

Not if you leave a trickle charger on it

 

[MoPar~Man]

So in short, based on that, is it a battery or alternator?

Also, are rebuilt alternators any good? They seem a little less pricey, but I don't wanna buy junk either, just something that keeps my battery charged.

The next time your 300 is running, with it not connected to your other car, measure the battery voltage. It should be 14 volts, maybe 14.5. But anything between 13.5 and 14.5 will tell you the alternator and voltage regulator is working. If you get under 13 volts it might be because the battery is really drained and needs time to come up.

A healthy charged battery that has been sitting for a few days or a week or two, in a car, at moderate temperatures, should read 12.8 volts. If there are various parasitic drains in the car, like a radio or clock or alarm system, then they're going to suck the battery down and after a couple weeks you might see 12.6 volts.

The first battery I had in my '00 300m lasted for 12 years - but I drove it every day, and it was always garaged overnight. Conventional lead-acid car batteries can last a long time, but they don't like to just sit, especially in the cold.

 

[Ross Wooldridge]

Agree to all that, with the caveat that they need maintenance charging to maximize their lifespan.

 

[Torky]

I'm a total newb on electrical things.

A few weeks ago, the 300 wouldn't start (1969 300, 440 K motor). Didn;t leave anything on or open, just turned the key and got two slow turns and that was it.

The battery's about four years old, I haven't driven the car but maybe 5,000 miles since I got it; once a week to work and toolin' around on weekends.

So I did a little research. They say the battery's supposed to show about 14 volts when the engine is running. But that's on new cars. Not much out there on the older ones.

I got my voltmeter out and checked my Honda. It's about 14.5.

The Chrysler battery was showing 12.06. I hooked the cables up (humbling, my little Honda starting the Chrysler) and it bumped up to about 13.2. Took several minutes and finally got the car started. After it ran for a little while, the battery was at 12.7. I shut it off, battery was at about 12.4. I let it sit for a few minutes, turned the key and it fired right up. Then it started to rain (no garage), so I couldn't test it any further.

So in short, based on that, is it a battery or alternator?

Also, are rebuilt alternators any good? They seem a little less pricey, but I don't wanna buy junk either, just something that keeps my battery charged.

Go to an auto store. Get a free test of your car's electrical system. May be several things wrong. Could be alternator (Unlikely), Voltage regulator (possible) battery (possible as batteries allowed to die completely can "sulfate off" (losing solid chemicals on the plates to drop off and short the bottom). Sometimes able to rejuvenate these dead batteries with a professional high-Voltage, High Amperage current. Don't count on it. T. or corroded battery terminals. Clean the terminals and the insides of the cable clamps before you go to the auto supply store to avoid embarrassment. Be sure you have a good battery terminal cleaner tool. If you have a lot of loose corrosion at the terminals, flush terminals and clamps with baking soda, then clean with fresh water and mechanically clean posts & clamps. Wear eye protection as the chemistry may generate splashing up.