Low voltage warning

So according to your post, an alternator has full output at idle, and any speed above that provides no additional voltage/amperage.
I suggest you try this basic procedure. Ground or bypass the regulator (for full alternator output) then test at 600 RPM and then test at 1300 rpm.
See how large the difference is,... because there will be a large difference. That's just a small test to prove my point.

And I beg to differ with you on Delco-Remy & the rest "telling me otherwise".
In fact, I'll provide just the first page of Delco-Remy's manual, which starts by referencing idle speed and alternator full output.
I guess Delco teaches their "classes" quite different than they provide in their corporate product and service manuals.




But please feel free to continue to do it your way... and I'll choose to keep doing it my way.

 

good luck with your way. cuz it hasn't been done since the alternator became internally regulated in the 80's.

but you go ahead. and don't cry when you fry the computer. cuz not only do you put out full amps. you also put out full volts. 24 to be exact.

i'll do things my way. the professional way. not the backyard way. i went to school. and i did the classes. and i was ASE certified.

but here's a bone for you to chew on. all them cop cars and ambulances that sit idling for hours with all those lights on. don't you think them batteries would go dead with your way of thinking. cuz i know they aren't sitting in there racing the engine up to keep the batteries charged.


yes out put increases. but the alternator still has to maintain battery charge while running all those lights.

 

No dog in this dicussion, but the Ford Crown Vic Police Cruiser has a special high output alternator, and a higher base idle RPM for long term idle with lots of accessories operating. I would assume all factory police vehicles have this also.

 

I'm quite aware of the differences is a variety of charging systems. Some have ECM's, some do not, some have ECM's control alternator output, rather than a typical regulator.
No one method will work on ALL vehicles. That I know. So it's up to you to choose what method is applicable for full alternator output.

My point, which I had hoped you would understand (but didn't address), is that the alternator will not put out it's full capacity at idle.
So it's common sense to also test it at full output.
The Delco-Remy page section, pertaining to full output and idle, contradicts your earlier post.

Good luck doing it your way also. I do it my way for reasons I stated. Apparent we agree to disagree.

 

all alternators are high output these days. 150 amps. that rear window defroster can take up a lot of power. and when your driving around the city. that's a lot of idling.

i'd hate to have my batteries go dead driving around the city in rush hour traffic. running all the accessories.in a snow storm. idling as your creeping along. only to find out from the mechanic that the only way to keep my batteries charged. is to make sure my engine stays at or above 1200 rpms.

can you imagine everyone using one foot on the brake and one foot on the gas to keep the engine up. really hard to do with a clutch car.

what cajunm speaks of would be somewhat true if you had an older car with external regulator. back in the 70's. alternators back then were only 75 - 100 amps. and rear window defrost didn't exist. or computers. but even then. cars would still charge. unless you were one of them guys that prefered to pollute the atmosphere by way of lowering your idle to some low number. say 700 rpms.

todays alternator doesn't test the same as yesterdays alternator. there's no way to bypass the regulator and put the alternator in full output mode anymore. now a days you need a battery tester to test the amperage. or just the plain and simple idle test. if it's not charging at an idle. it's bad.

not that hard of a concept to figure out.

but cars idling at 700 rpm. is a thing of the past now. todays computer keeps the engine around 1000 rpm. no way you can change that. unless something is wrong.

bottom line is, engine spins fast enough. and alternators are much higher amps then yesteryear. and i think everyone knows by now. that a normal system with all accessories running will show 14 volts. most cars and trucks DO have dash meters to see that.

if my truck or car shows 13 volts at an idle. i'm replacing that alternator. even though cajun says it's just fine. cuz i know it's just a matter of time before i get caught with dead batteries.

 

snowwy,
Why do you inject your numerous very false "assumptions" on any of my posts?
My information has nothing to do with only vehicles of the 70's and 80's. For you to assume that is laughable.
I began mechanic work in the 60's, but still do it today, over 40 years later. And I'm definitely not "stuck back in those days".
Also, don't assume any criteria I use to know if an alternator is good or bad. You're assuming wrong because you have no idea.

Your last post is riddled with inaccuracies, almost too many to count.
Idle speeds are STILL spec'd by factory anywhere from 600 RPM, on up. Not 1000 rpm for everything. This topic isn't limited to your jap bike, your cavalier, or your KW.

Alternator pulley diameters also come into play, for effective alternator speed (rpm's). The higher amperage of present day alternators is needed for increased electrical loads on present day vehicles, so it's all still apples to apples, compared to simpler vehicles of past days.

Still it seems, you refuse to even comprehend the important line written in the Delco-Remy manual, which I reference because you brought it up about being "trained" by them.
Please see what it says in the yellow highlighted areas. Everyone else can see it, but apparently not you.

BTW, alternator testing is virtually the same as it was years ago. But it's up to the competent mechanic to know the charging system he is working with, to safely test it.
If an alternator requires it be isolated or bench tested for full output, it all depends on the vehicle and/or charging system.
So when I say to ground/bypass the regulator to test for full output, I shouldn't have to explain to you what proper steps you need to do to safely do it.
You know that every vehicle and charging system is different.

I'm not going to carry on this debate with you any further. Just don't post things relating me to your false assumptions.

 

coming from a backyard mechanic.

 

Considering you don't have any knowledge of my mechanical background, I'd say that statement is the height of irresponsibility and error.
Not hard to see it was said out of anger because even "your educational source" showed you wrong.
But I forgive you. Please no more "cheap baiting". I'd hope you were better than that.

 

no. your statement was the height of irrespsonsibility.

my false assumptions never once diagonosed a problem wrong. or had to fix a charging the system a second time. and they wouldn't dream of bypassing the regulator. as that would burn out the computer. and my false assumptions used nothing more then a voltmeter.

my false assumptions also know that a engine idling at 800 rpm is gross polluter and would burn out the catalytic converter. my false assumptions also did emissions testing. and kjnows that todays vehicles are computer controlled to idle between 1000 - 1200. minus the semis.

i don't really care about your mechanical abilities. i know how i fixed things. and i did it for TWELVE years. under false assumptions. as you kindly say.

 

Have your batteries load tested. Freightliner has updated their batteries for EPA 10 engines. Check the part number on your batteries. If they are the 8A31 batteries, they are the ones that were installed, but are losing electrolite. If a shop installs new batteries, make sure they are the 9A31.