Testing Alternator

[super99]

I moved the 1850 today and noticed that it wasn't charging. It has always charged good but it would squeel from time to time when first started. I think it was replaced around 07. I have a multi meter and a battery load tester, is there any way to check why it's not charging or just replace it? It has a voltage regulator also if that matters. Thanks, Chris

 

[rustred]

check your voltage across the battery while the engine is running. should have over 14 volts up to 14.8 max. if its charging. if its not charging it will show 12 volts or less. the squeeling is due to a loose belt. and that can be why its not charging the battery. if you can turn the alternator fins by hand the belt is not tight enough. it takes a few h.p. to run a charging alternator, not like a generator where it will charge with a loose belt as long as its turning. put a load on the battery once its charged up to see if its any good. it should hold the load for 10 seconds at the cranking amps . if it just drops to the low side of amps the battery is no good or not charged one or the other. a junk battery will not even accept amps while trying to charge it. or it will but just drop right off once load testing it.

 

[Den N Ms]

Super99 , I would consider replacing the old style Delco 10 DN and regulator with a newer style Delco 10 SI one wire self exiciting alternator with a built in regulator.

 

[old]

Start by checking the battery not running. It should show 12.6 plus if good and full charged. If less then it is not at full charge. Next fire it up and you should read 13-15 volts depending on the load and how fast you check it after starting.

 

[rustred]

and i will also add the most common problem is the brushes wear out and thats all it takes to get it charging again. brushes and a bearing or grease the old ones. on time the brother in law pulled in the yard and said his alternator quit. i removed it and replaced the brushes and it worked perfectly .then he said what do i ow u. i said 3.00 but never mind. that was the price of the brushes in the 1980's right from g.m.

 

[rustred]

yep, i said that. but 15 volts is too much.

 

[PJH]

''but it would squeel from time to time when first started''

Belt loose?

 

[MarkB_MI]

Assuming the charging voltage is low, the next thing is to figure out if the problem is the regulator or the alternator. Most alternators have a way to bypass the regulator. Typically you stick a screwdriver in a hole in the back of the alternator, shorting a metal tab to ground. If the voltage comes up when the regulator is bypassed, then the regulator is bad.

Note that it's possible for a bad alternator to blow the regulator. BTDT.

 

[Jim.ME]

If this is a Delco 10DN externally regulated alternator (you have not identified what alternator you have, but 10DN was common on equipment) the two prong connector goes in the back, not the side.

After checking/adjusting the belt, unplug the two prong connecter.

Test to see that the alternator battery terminal has battery voltage.

With the engine running, use a jumper wire between the battery terminal of the alternator and the field terminal (spade terminal on the right in the back of the alternator should have an "F" near it). That will full field the alternator. If the alternator is good, you will normally get a spark and charging will jump up. Do not run it long using the jumper as it will go high on voltage not having any regulation. If the alternator charges the problem is likely the regulator or wiring.

 

[Steve@Advance]

I'll second the upgrade, do away with the external regulator.

It's an easy swap, same physical size and mount. Minor wiring mod if you go with the 3 wire. Probably cheaper too!

 

[Stuart]

Not true. The two alternator repair shops I use now go with a range of 13.2-15 volts. I have seen this on old tractors with alternators and late model cars. It has never boiled the water of of the battery

 

[Steve@Advance]

If it is a Delco, (or any alternator) check for voltage at the BAT terminal on back of the alternator. That should be a direct connection to the battery and battery voltage all the time.

Unplug the regulator, jump from I to F terminal of the harness. Engine running, up to speed, belt tight, that should make it full charge if the alternator is good. Be sure there is voltage at the I terminal with the ignition on. If that makes it charge, good chance the regulator is bad.

I would consider upgrading to an internal regulated alternator, easy change, minimal wiring mod, more available, and cheaper.

 

[Hobo,NC]

(quoted from post at 09:44:31 01/04/23) ''but it would squeel from time to time when first started''

Belt loose?

The first place I am headed... Its talking to ya.

 

[Mike(NEOhio)]

Check the brushes and slip rings. I used to drive Scouts and about every couple of years I would notice the wipers slow and headlights dim. I'd pull the alternator, 10SI, and polish up the slip rings and new brushes if needed.

 

[Geo-TH,In]

If it's charging the voltage must increase.
I would take the alternator to Autozone.
They will test it for FREE.
I buy lifetime alternators from Autozone..

Not all digital voltmeters can measure the Alternator voltage accurately.
This one can. Use an old analog meter or if you have a load tester with a voltmeter use it.

The meter on the carbon load tester can measure the charging voltage.

 

[Russ from MN]

The 2013 Chevy Silverado that we sold last fall charged at 15 volts most of the time, and the original sealed battery lasted 9 years, and I changed it because of age, not because it failed.

 

[rrlund]

I've had to tap on the regulator on mine. I'd sure try it before I spent any money on it. In fact, when I was picking corn a few months ago, it stuck and was over charging. I could smell sulfur. I noticed the gauge was pegged. I tapped the regulator with a wrench and it dropped back to normal.

 

[sotxbill]

Built-in Temperature compensation for maintaining the set voltage output over the expected ambient temperature range

The regulated output voltage of the alternator is set normally to generate around 14 volts for vehicles using a nominal 12 volts system. This is to ensure that the alternator will be able to charge from a sufficiently higher voltage level even as the battery voltage keeps increasing with progressively higher levels of SOC. Apart from the alternator output voltage the batterys capacity to absorb charge also depends on the rate of chemical reaction in the electrolyte. The rate of chemical reaction is dependent on the ambient temperature. The experience of the vehicle power system designers has been that the charging efficacy of the system can be improved by marginally modifying the set point of the voltage regulator to be more at colder temperatures and lower at higher temperatures; the aim is to compensate for the changes in the rates of reaction in the battery electrolyte by having an automatic voltage setting mechanism in relation to the ambient temperature. The alternators now have regulators with a temperature compensation circuit to dynamically change the setting of the regulator with respect to the ambient temperature. A typical graph showing the compensation is given in Fig 3.7 .

Sketch 3

Fig 3.7 Typical graph of temperature compensation for voltageregulator setting

The automatic in-built compensation ensures that when the ambient temperature is cold the alternator voltage is enhanced to compensate for the reduced chemical reaction time of the electrolyte by driving the charging at a higher voltage. Similarly at higher ambient temperatures the output voltage is reduced to compensate for the increased chemical reaction time of the electrolyte so as to avoid overcharging and gassing in the battery.

 

[Hobo,NC]

(quoted from post at 20:10:52 01/04/23) The 2013 Chevy Silverado that we sold last fall charged at 15 volts most of the time, and the original sealed battery lasted 9 years, and I changed it because of age, not because it failed.

15 + V's would push the limit on a tractor, your late model pick'em up consumes most of it when the system is loaded. That is if we assume the in dash are meter used was accurate and take into account the alt on it is 2,3,4 times the dynamo on a tractor.

When I first ran across 15V regulators they were made for emergence vehicles. Under normal circumstance 15V throws up a flag. The safe zone on the high end with a accurate meter 14.5 to 14.6 I may not chase a 14.8 are your 15 if there were no concerns.

That squeal he has is taking : ) No on vehicle operation test will be accurate if the belt is screaming.

 

[JMOR]

Maybe this info from GM manual will help Old & rustred quell the bickering:
Set for 14.2 to 14.6
Acceptable for use: 13.5 to 15.2