cucv generator

[63bravo]

cucv blazer charging at 29.3 volts , sounds a bit high to me ,so what do you guys think ??

 

[markg]

Nope, right on the money. check each battery with a vom. 14.6 times 2 is...?

 

[63bravo]

thanks , its good to go !!, I blew of a date with the girlfriend to work on my cucv , LOL

 

[TechnoWeenie]

Nope, right on the money. check each battery with a vom. 14.6 times 2 is...?

14.6 is high

13.8 is nominal.

 

[markg]

14.6 is high

13.8 is nominal.

For this application 14.6 is the high number with no load. i think the range might be 14.2-14.8. 13.8 would not keep the battery charged. others vehicles are different. thanks. mark

 

[scottladdy]

From the -20 page 2-60:

9. VOLTMETER IN RED (OVERCHARGE) ZONE (ALL EXCEPT M1010)
Step 1. Start engine. Check voltage at left and right alternators at positive (+) terminals.
Voltage should not exceed 16.0 at left alternator or 31.8 at right alternator.
If voltage is over 16,0 at left alternator or 31.8 at right alternator, replace
alternator. (See paragraph 4-2)
If voltage is correct, replace voltmeter. (See paragraph 4-9)

 

[markg]

From the -20 page 2-60:

9. VOLTMETER IN RED (OVERCHARGE) ZONE (ALL EXCEPT M1010)
Step 1. Start engine. Check voltage at left and right alternators at positive (+) terminals.
Voltage should not exceed 16.0 at left alternator or 31.8 at right alternator.
If voltage is over 16,0 at left alternator or 31.8 at right alternator, replace
alternator. (See paragraph 4-2)
If voltage is correct, replace voltmeter. (See paragraph 4-9)

i hate to disagree with the tm but 16v for a period of time will cook the battery. not a pretty site!!!

 

[scottladdy]

i hate to disagree with the tm but 16v for a period of time will cook the battery. not a pretty site!!!

markg, thanks for pointing out that lead acid batteries are sensitive to charging voltages. A good article on charging system design and the compromises made by engineers:
http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

Note that the section of the -20 I referenced is actually an updated section of the TM (black vertical bar on left margin). The voltage is read directly off the alternator positive terminal in reference to ground.

The -34 Alternator testing and repair page 4-8 states:

6. Turn on fast charger (43) and slowly
increase charge rate. Observe
voltmeter (44), Test lamp (46) should
go out at voltage regulator (12)
setting. Voltage regulator setting
should be a minimum of 13,5 volts
and a maximum of 15,5 volts,

The specified replacement voltage regulator for the 27SI type 100 has a Vset of 14.8 volts.
http://aspwholesale.com/index.php?act=viewProd&productId=1650
(check specifications tab)

My point in elaborating on this is that there are a considerable number of variables in the charging system of any vehicle. The TM indicates a diagnostic procedure deemed "acceptable" by the military for the maintenance of these vehicles. And while there are errors in any publication, I think this one is correct. Remember that alternators have more than one job. They power the vehicle AND re-charge the batteries. The battery does act as a source of power during those moments when a load is switched on before the alternator's regulator has had a chance to adjust the field coil, and as a sink for when loads are switched off. But aside from starting, the alternator (if working properly) does the long term heavy lifting. It is a very different environment than a bench charge environment.

So, the short of this is I agree with your assessment that a constant charging voltage of 16 volts would be detrimental to a battery, especially if being bench charged. The dynamics of an operating vehicle indicate a very different set of conditions, however. Conditions that maintenance and repair manuals are likely to have taken into consideration.

In addition, there isn't a single charging process that is ideal for all the different types of lead acid batteries commercially available. Contrast the Battery University article I referenced above with the charging procedures specified by Optima for their AGM batteries: http://www.optimabatteries.com/en-us/support/battery-care/charging/

One last point: 14.8 * 2 = 29.6 volts.

Respectfully submitted ...

 

[Hasdrubal]

My recently rebuilt alt2 only reads 14.2V. While it is within spec..the voltmeter gauge does sit lower than where it had previously always indicated on the hash mark. Does this point to a possibly faulty or wrong regulator. I've also have a morse code flashing alt2 light at idle that bothers me. The shop is not helpful. Considering replacing the regulator, diode trio and rectifier my self, for good measure.

 

[doghead]

There are several regulators with set points varying from 14.0-14.8 volts that are very common.

 

[scottladdy]

My recently rebuilt alt2 only reads 14.2V. While it is within spec..the voltmeter gauge does sit lower than where it had previously always indicated on the hash mark. Does this point to a possibly faulty or wrong regulator. I've also have a morse code flashing alt2 light at idle that bothers me. The shop is not helpful. Considering replacing the regulator, diode trio and rectifier my self, for good measure.

There are several voltage regulators available for the 27SI, some with different Vsets. It is possible your rebuild used a different part.

As far as the flashing alt 2 light, start simple and check belt tension, pulley and belt wear and engine idle speed. Make sure all connections are clean and tight etc.

I would not hesitate to rebuild your alternator if you are not comfortable with the shop. Follow the sage advice in this forum and you should be fine. Brushes are cheap, and while you have it apart ...