how many volts does your battery read?

dillenrocha · 08-15-2011, 08:07 PM

So my alternator was not charging and after a long time of searching I found out it was my gauge light. So I was wondering what everyone battery reads at idle. My battery read a little below 14 with everything off. Then a little over 12 and half with ac on fullblast and head lights up. Is that regular?

mikepellegrini · mikepellegrini's Garage

With the car off it should be around 12 VDC. With the car running it should be in the 13-14 volt ballpark.

AA_Ezra · 08-16-2011, 11:45 AM

i have not checked mine in forever but the batter should Read 12+ volts like 12.2-3 volts with car off. These cars, the early model anyways runs about 13.? volts running. I got an adjustable voltage regulator and set it at 14.3-.4 or so, car ran better and lights were brighter. But i also upgraded all my wire to 4 guage wire and that helped even more

dillenrocha · 08-16-2011, 12:03 PM

Yea everything off it was running around 14 but with radio lights. And ac full blast it was about 12.5 is that normal or should I check some other places?

AA_Ezra · 08-16-2011, 12:44 PM

That might bevnormal honestly I'm not sure.I've never tested the system with my ac on. But if I did I would probably take up the idle to 1500-2200 rpm to get an accurate reading as if the car was running. There could be a bad ground maybe?

There was a recent thread maybea few seams ago were the issue ended up being the secondary fan that's turns on high with the ac on was not spinning as easily as the other and was causing a high load/draw making the voltage drop. Easy thing to check. Spin the fans with the car off and cool. Or disconnect the harness and check them that way. Should spin freely and no grinding noises

racer · 08-16-2011, 01:08 PM

I see between 12-14 on the dial on mine.. seems to not move much despite electrical load (ie fans, ac, radio, lights or combinations thereof, but I will try to look more accurately next time.). Mines an '87 base model.

AKCJ · 08-17-2011, 10:34 AM

Quote:

Originally Posted by dillenrocha

Yea everything off it was running around 14 but with radio lights. And ac full blast it was about 12.5 is that normal or should I check some other places?

The 12.5 volt running voltage is low (even with the load), however, it may just be because the car was at idle. Try running the engine speed up a bit and see if that reading goes up. It's common for an alternater to not put out much at idle.

dillenrocha · 08-17-2011, 05:26 PM

Yea when. I rev it it comes up but when I let of. The gas off it goes. Back.

Aufgeladen944 · 08-17-2011, 05:40 PM

If I don't have anything on, it's around 13. If my lights are on and the stereo and whatnot, it's at 12. I had the idiot light come on for the first time on Sunday when the gauge dipped below it for a couple seconds. Made me nervous...

Of course, I wouldn't be surprised if the gauge itself wasn't working correctly, either.

redstrosekNic · redstrosekNic's Garage

Should always be 12.6v when off, and between 13 & 14 when running. I know of many cars that actually discharge slightly when at idle. If the volts come up when the engine is at about 1100 rpm, I wouldn't worry about it.

VirginiaF1 · VirginiaF1's Garage

Quote:

Originally Posted by Aufgeladen944

If I don't have anything on, it's around 13. If my lights are on and the stereo and whatnot, it's at 12.

Of course, I wouldn't be surprised if the gauge itself wasn't working correctly, either.

My numbers are the same under identical conditions... original gauge from factory.

AKCJ · 08-18-2011, 08:02 AM

Sounds like you're ok if the voltage reading goes up with engine revs.

If you want to dig in to it more you could always pull the alternator and check the brushes.

Aufgeladen944 · 08-19-2011, 02:02 AM

Bleh the light came on again while driving to work yesterday. I can see the alternator from under the car.

That a hard job to do? Any surprises on getting that thing out?

AKCJ · 08-19-2011, 08:13 AM

Those alternators don't last forever - do you know how many miles are on it?

I have had much better luck rebuilding the original alternator rather than getting replacements - at times the rebuilt units from NAPA are really, really, bad.

You can do a search to get rebuild info - replacing the brushes and bearings is usually fairly easy. If you don't want to do it yourself you can take it to an automotive electric rebuilder.

I can't help with your question about getting it out as I'm not familiar with the Turbo like yours. On my 83 I just started taking stuff out from the top down until I eventually got down to the alternator - it took quite a bit longer than on most other vehicles but was just basic removal. Nothing too difficult.

Aufgeladen944 · 08-19-2011, 04:12 PM

Seems like going at it from underneath would be easier. And I'm definitely going to bring it somewhere to rebuild it, rather than going to Advance or whatever.

mxfrank · 08-20-2011, 03:25 AM

First thing I would do is clean the battery terminals and alternator connectors. Then use a hand held multimeter to read voltage across the battery terminals, which will be more accurate than using the dash gauge.

Bosch regulators are temperature compensated...meaning that as the alternator warms up, the regulator will reduce charge voltage to avoid diode damage. As a result, you will probably see around 14V cold, which usually drops to around 13 and change when the car is warm. If you find that you are getting less than 13, then the first thing to try is replacing the brush/regulator pack. This is an easy job to do, without removing the alternator. Remove the air intake duct on the rear of the alternator, and the regulator pack is held in with two screws. When you remove the old pack, you will be able to reach the slip rings. Run some contact cleaner over the slip rings, which may have deposits of carbon and oil. Install the new pack and you should be good to go.

If none of this helps, you can always replace the alternator.