What is normal voltage?
- Thread starter lyonsd
- Start date
I used to work in the alternator lab at Delco-Remy a few years back and as I remember, the output will be around 14.65V on the CS-144 alternator. That was in a cold condition. When the unit gets hot, the voltage will drop down some. As for the SM reading, I don't know where the ECM goes to get that reading. I would suspect it comes from the point at which the 12 volts comes into the ECM so that really isn't exactly what the alternator is making or what the battery voltage might be. To check things, put a good DVM at the output stud on the rear of the alternator and compare the 2 measurements. Something else to try, put the + meter lead on the stud and the - meter lead on the battery's + terminal and look at the voltage drop in the wire between the 2. It shouldn't be very much with things turned off. With stuff turned on, I wouldn't expect over half a volt or so. You can always increase the wire size to keep that drop less.
David
David
Steve Wood
Active Member
- Joined
- Jul 18, 2001
First thing you need to do is to check the voltage with a voltmeter at the alternator as the Scanmaster can be reading a lower voltage due to circuit resistance. You may find that you are actually putting out a couple of tenths, or more, voltage than the SM is seeing. It does not sound bad at all to me, tho'.
Can someone help me please!!!!! 
i am losing my mind here! Car had a battery dieing problem when all accesories on the car were turned on. Bought a new battery and monitered SM 2. Also turned on all accesorries and measured voltage at battery. It was 11.7-12.7 range i think.
SM was showing #'s in the range of 10.9- 12.8 most of the time. Barely hits 13 volts. So i bought an Impalla 140a alternator today and installed it. Numbers were in the 13-14.1 range.
I was happy. But a few minutes later numbers were fluctating between 11.7v- 13.3 volts. It mostly stayed around 12.7 volts. With key in i do have a volt light on.
After bringing my old alternator to autozone as a core i told them to test it and they said it was fine. I decided to keep the new alternator since it looks good and i already put the work into installing it.
I do not know where to go from here.
i am losing my mind here! Car had a battery dieing problem when all accesories on the car were turned on. Bought a new battery and monitered SM 2. Also turned on all accesorries and measured voltage at battery. It was 11.7-12.7 range i think.
SM was showing #'s in the range of 10.9- 12.8 most of the time. Barely hits 13 volts. So i bought an Impalla 140a alternator today and installed it. Numbers were in the 13-14.1 range.
I was happy. But a few minutes later numbers were fluctating between 11.7v- 13.3 volts. It mostly stayed around 12.7 volts. With key in i do have a volt light on.
After bringing my old alternator to autozone as a core i told them to test it and they said it was fine. I decided to keep the new alternator since it looks good and i already put the work into installing it.
I do not know where to go from here.
salvageV6
Daily Driver
- Joined
- May 25, 2001
A fully charged battery doesn't need or want to see 14 volts.
First you need to know if your battery is charged or not.
Load on the car with accessories will also vary the alternator output both with a fully charged and an almost dead battery.
A simple test of the alternator is a good digital meter that is easy to read, start the car and read at the back of the alternator and then read at the battery keeping the same ground at first.
If you are off more than a coupla tenths I would seriously look into the line that feeds the battery directly from the alternator. It is known to be a bit small and prone to losing some conductors over time.
Just my .02 you need more testing than simply looking at a scanmaster.
Grounds are another topic.
First you need to know if your battery is charged or not.
Load on the car with accessories will also vary the alternator output both with a fully charged and an almost dead battery.
A simple test of the alternator is a good digital meter that is easy to read, start the car and read at the back of the alternator and then read at the battery keeping the same ground at first.
If you are off more than a coupla tenths I would seriously look into the line that feeds the battery directly from the alternator. It is known to be a bit small and prone to losing some conductors over time.
Just my .02 you need more testing than simply looking at a scanmaster.
Grounds are another topic.
Just went out to check voltage levels again.
When car was started SM was reading 13.3-13.8
Voltage at battery was around that same area also if not higher.
I turned on headlights, heater on high, rear window defroster and radiator fan on. This simulates conditions in which i experienced a nostart after parking the car on a rainy day.
Voltage at battery with negative post as a ground reference is 12.5v. At the alterenator with the same ground reference it was 12.8v. Sm was showing volts between 10.3-10.8. When makeing the measurements voltage is not steady, it jumps around alot, usually +/- .5volts.
Checked the big ground cable and traced it back to the engine block. Bolt and cable look okay. There is alot of grease there though, so i am gonna spray some type of degreaser.
There is a hot wire that is 10 or 12 guage wire that runs straight to the alternator. By the battery end there is 3 inches of uninsulated wire that is sligtly rusty looking.
What next Change the battery cables?
The only other thing i can think of is maybe the exciter wire is not doing its job poperly. Maybe get a repair end plug for the alternator and attach it straight to the battery and see what voltages im getting. Or maybe if there is a test hole in the alternator, put a screwdriver in there to make the alternator give out full voltage?
When car was started SM was reading 13.3-13.8
Voltage at battery was around that same area also if not higher.
I turned on headlights, heater on high, rear window defroster and radiator fan on. This simulates conditions in which i experienced a nostart after parking the car on a rainy day.
Voltage at battery with negative post as a ground reference is 12.5v. At the alterenator with the same ground reference it was 12.8v. Sm was showing volts between 10.3-10.8. When makeing the measurements voltage is not steady, it jumps around alot, usually +/- .5volts.
Checked the big ground cable and traced it back to the engine block. Bolt and cable look okay. There is alot of grease there though, so i am gonna spray some type of degreaser.
There is a hot wire that is 10 or 12 guage wire that runs straight to the alternator. By the battery end there is 3 inches of uninsulated wire that is sligtly rusty looking.
What next
Change the battery cables?The only other thing i can think of is maybe the exciter wire is not doing its job poperly. Maybe get a repair end plug for the alternator and attach it straight to the battery and see what voltages im getting. Or maybe if there is a test hole in the alternator, put a screwdriver in there to make the alternator give out full voltage?
Originally posted by dpok69
What next
Yep. It's a pretty cheap try anyway.
I has similar problem with my mom's Passat. I could charge the battery, and she would last about 2 weeks. Replaced the battery and alternator, not fixed.
Then I started the car, checked the voltage at the alternator - > 14v. Then I unhooked the positive battery cable and checked the voltage supply there - ~12v. Enough to keep things going for a while, but it was not enough to recharge the battery after a start and running the cooling fan after shutdown in summer.
LONG story short, I replaced the positive cable to the battery, and VIOLA, problem solved.
Um, trust me, there is no way to simply adjust the output of a CS-144 alternator short of changing the regulator in it. Unless you like seeing sparks or buying alternators, I'd keep the Golden screwdriver out of it.
There are a couple of things you can do to "fool it" into increasing the output voltage, but they're a bit involved and require some wiring external to the unit.
David
