Low Volts/Charging issue?

[Pliskin1]

Details of the car are in my signature. I should add to my signature line that I'm not very handy with a wrench, but I can get by on basic stuff.

Out for a ride yesterday. Scrolling though the scanmaster just to check things. Had the A/C on, and noticed volts were reading about 12.5 to 12.6 at 18oo-2000rpm. Shut the A/C off, volts went to about 13 to 13.1, even at higher rpms.

Went home and checked with voltmeter. Reading 12.5 with car off. Charged for several hours, reading 13.2 at the battery with engine off. (Haven't checked at idle). I know each cell is designed to hold 2.1 to 2.2V, so at a minimum I should be at 12.6 with car off, and preferably closer to 13.2, so I'm right there after charging.

Battery was new as of March 2014.
Always on a trickle charger.

I'll probably get the battery load tested to be certain, but I'm thinking it might be my alternator. Would you agree? Are these cars known for any grounding issues that I should look into?

If I do have to change the alternator, suggestions on brands or upgrades?

Thanks in advance.

 

[Boston GN]

Does the volt light on the dash turn on when you have key on car off?

 

[Pliskin1]

Does the volt light on the dash turn on when you have key on car off?

I didn't notice it, but then again, didn't specifically look. (Can check that tonight when I get home from work).

 

[Boston GN]

As simple as it is, it's very important to our charging systems. That light completes the circuit, so if the bulb when out, you're not charging.

 

[Pliskin1]

OK, thanks. I'll definitely look tonight with the key on, car off. Should the light stay on the entire time that the ignition is turned, or does it only stay on momentarily?

On the assumption that it does light up, does that then point to the alternator?

 

[mikestertwo]

There is probably nothing wrong. That voltage reading is ignition voltage not battery voltage. I'm assuming the ambient temperature was warm being you had the air conditioning running. There is temperature compensation in the charging system. What is the voltage reading when you start the car cold in the morning?

 

[Nick Micale]

[QUOTE="Pliskin1, post: 3576983, member: 46251................... Scrolling though the scanmaster just to check things. Had the A/C on, and noticed volts were reading about 12.5 to 12.6 at 18oo-2000rpm. Shut the A/C off, volts went to about 13 to 13.1, even at higher rpms.

Went home and checked with voltmeter. Reading 12.5 with car off. Charged for several hours, reading 13.2 at the battery with engine off. (Haven't checked at idle)..........[/QUOTE]

I see you are relatively new to the board, but many times, myself and others, have stated the the Scanmaster is NOT an accurate display of alternator output.

There is a very simple reason for this, the SM reading is lower than the voltage at the alt which is because the SM is grounded to the body, not the battery?

Also, it is very common for a good battery to slightly "recharge" itself sitting after a period of being charged by driving the car, but I do not remember seeing 13 volts or more at the battery after the car has been inoperable for a short time?

Just to be sure I was not "dreaming" about this, I just checked battery on my 2 month old F-150 and the battery voltage is reading 12.3v overnight.

The new charging system analyzers most parts store utilize can provide all the data you need with a couple minutes of testing to determine if there is an issue in the system.

 

[Pliskin1]

There is probably nothing wrong. That voltage reading is ignition voltage not battery voltage. I'm assuming the ambient temperature was warm being you had the air conditioning running. There is temperature compensation in the charging system. What is the voltage reading when you start the car cold in the morning?

Correct, ambient was about 85* yesterday when I was out.

I understand you are saying its ignition voltage, but even when I got home, shut off the car, and read voltage directly at the battery is was only 12.5-12.6.

Every time I start/drive the car, I always cycle through the SM just to check and make sure all seems well. Historically, the voltage on the SM reads anywhere between 13.4 and 13.7, as it did when I left the house yesterday, but this would also be a reading right after being removed from the trickle charger. (I typically only drive the car once a week, so that's part of the reason the charger is always on it).

 

[Pliskin1]

Thanks Nick. For some reason (probably user error!) I didn't see your post at 11:55 even though I posted at 12:06.

I understand what you're saying about the SM not being too accurate. I did not install the SM myself (Jim Dunn did) so I don't know what its grounded too.

I'm certainly not the type of person to just randomly throw money at problems without doing the basics first. That's why I lean on you experienced forum guys!

Thanks for the info.

 

[Pliskin1]

Does the volt light on the dash turn on when you have key on car off?

To confirm, volt light on dash does light and stays lit.

 

[Flyin Brian]

Check the voltage at the battery with a voltmeter with the car running. It should be over 14 volts if the alternator is working right.
You really should not need a trickle charger if you drive the car once a week. I let mine sit for 3 or more weeks at a time and it starts and runs fine. I usually then try to drive it for a half an hour or so to charge the battery before I park it again though. My battery will read over 13 volts right after I take it off the charger but will drop back down to 12.6 or so after a day.

 

[Pliskin1]

Check the voltage at the battery with a voltmeter with the car running. It should be over 14 volts if the alternator is working right.
You really should not need a trickle charger if you drive the car once a week. I let mine sit for 3 or more weeks at a time and it starts and runs fine. I usually then try to drive it for a half an hour or so to charge the battery before I park it again though. My battery will read over 13 volts right after I take it off the charger but will drop back down to 12.6 or so after a day.

I was getting about the same readings of 13.1 to 13.2 with the car at idle, after driving it for about 30 minutes. That's with the voltmeter at the battery, car running.

Realize it's not necessary to have it on the trickle charger, but I don't think it hurts. (?) Its just a small 1.5amp trickle.

 

[Flyin Brian]

13.1 volts at battery with car running seems a little low to me. You can try checking it at the post on the back of the alternator.
Leaving it on the trickle charger should not hurt anything.
You might check and be sure your battery cables are clean and tight on the battery.

 

[Pliskin1]

Thanks, everyone, for your replies and advice.

I'll definitely do a little more investigating and do the simple things that were suggested. As I mentioned, I'm not really inclined to throw a new alternator in it right away just because the readings seem a little low.