77 ford f 250 w/ 460

alternator tested and is good - but might (not sure) be from previous 400
mechanic can pinpoint problem- but wants anywhere from 24 to 50 dollars
could by voltage regulator - should i just buy and see if that works
could by my wiring - will go over again to make sure

motor stays running after unhooking the battery?
i'm not experience w/ checking the voltage w/ any gadgets.
was wondering if the alternator is not the right amps. looked on LMC and they show a 60 amp and 100 amp alternator.
can see a pic of the alternator in my gallery.
is there a way to identify which alternator i have?
truck will run good w/ charged battery for a while.

 

Never unhook a battery while the engine is running! Take your truck to the nearest Advance Auto Parts and have them test the charging system and battery. Get whatever part they recommend. The alternator is stamped with an Amp rating.

 

You may have already pooched the alternator by UNhooking the battery cable while the engine was running

Spend $10.00 on multimeter and do tests before jumping to conclusions.

Note: You can quickly see if the charging system is working by hooking up a multimeter to the battery and revving the engine up.

Now you have to go to a shop to see if you destroyed the alternator.

The charging value of the alternator is not a factor here,

Higher alternator values are required on vehicles with a greater need for more amperage.
Things like power windows,power seats and Massive Amplifiers on E-series vans.

They are not needed on pickups .
40 amps is okay.

The case of the alt has the amperage value stamped right on it. look for * 40 amp *

 

Just curious... what happens when the battery is unhooked while the engine is running that makes the alternator go bad? And is it ok to jumpstart a truck with a dead (junk) battery and run the engine with the alternator power even though the battery is junk? I'm just wondering how this works so I don't fry any alts in the future.

 

nearest advanced auto is 80 miles away. i'm not sure how to use the multimeter. i'll buy one tomorrow and go from there. if i cannot figure the multimeter out, i'll post for help. any advice would be welcome. thanks.

 

put the meter on dc volts red (+) to positive post of batt black(-) to negitvie post of batt should read abuot 14.2 volts at 1000 rpm (high idle)

 

Check for a bad voltage regulator plug.My plug was so rusted it was making an intermittant charging problem.A new voltage reg. a few snips later and 4or5 crimps problem solved.Almost forgot use a crap load of die electrical grease.


Tim

 

finally got to look at the truck again. before starting tested the battery and got a reading of 12.? and than started the truck at a high idle and got a reading of 15.?
after turning it off again tried a reading and got alittle over 13.?
sorry i can't remember the actual readings.

 

That sounds like it is charging to me.

 

O'Reilly's and Auto Zone will do charging diagnostics, also. You may have one of those closer than an Advance store.

 

There is a HUGE difference between a battery that is good enough to start and engine and good enough to power a radio.

That voltage at high RPM tells me the ALT and VReg are doing their job...but the battery itself may not be accepting that amount of current.

That's why one has to Fully-charge a Battery using a battery charger (not relying on alternator charging) before it's tested at a Automotive shop where it is put through vigorous testing on a special machine to determine what shape the battery is really in.

The Battery is like the human Heart.

If it isn't in great shape...the symptoms will show up.

 

Yeah, what JimLJ said. :)

15's a bit high but who knows how accurate your meter is etc. :)

Working in the desert has taught me to blow on the meter face before expecting it to read right. :/ Yeah, glass-faced ones too. :/

But you got all the readings you needed for the trouble you were searching for. :)

Another test is to poke the meter leads into the battery's terminal posts and have someone crank over and start the engine... check out the readings as the needle moves... how -low- did the voltage go?

If the engine didn't turn over and the voltage went low (9volts?) then you have a low battery. If the engine didn't turn over and the voltage remained high... you have a bad connection somewhere. That bad connection is easy as pie to find with a meter! :) No kidding and no guessing on where it's at either.

After finding and fixing a bad connection, start from sctrach and do the test again. I've found two bad connections twice and both times it involved the type-of-clamp where -the cable is clamped to the clamp- using two 1/4-20 bolts.

One gal thought she had a bad battery since she'd taken off and cleaned her clamp-to-battery-terminal connections and made no difference. I removed and cleaned her cable-to-clamp connections and the car fired right up like it had a -new- battery.

What a difference a dumb little ol' meter makes huh? :)

Everybody that's got an old clunker -like we do- needs to have an analog meter and know how to use it... at least a little.

You can learn that right here... and no "charge;)" neither. :)

"shoulda learned Ohm's law and how to use a meter in algebra class" -alvin

Alvin in AZ (retired RR signalape)

 

seems like my alternator and volt regulator is good. i'll check the wiring again. don't have a short because then my battery would be dead in the mornings. just fishing alittle. my uncle thinks it could be something to do w/ the fuel system. he said it sounds like it's not getting enough gas, but that wouldn't cause the battery to die all the time would it. did find a small leak on the carb base plate. bought one just need to replace it. and we don't see any gas squirt into the bowls when stepping on the pedal. the truck will run fine w/ a charged battery w/ no problems. just after a while the truck will die. will start w/ a jump alittle gas in the carb. well i'll be reading some more, maybe vapor lock? i dah no

 

Do like Mil1ion said, charge the battery with a battery charger till it is fully charged and have it tested. It sounds from your discription that you have a weak battery. If the battery tests good, have the starter tested as that would also cause the problems you describe.

 

[quote]i'll check the wiring again. don't have a short because then my battery would be dead in the mornings. just fishing alittle.[/u]

It seems you missed my point,.

NO. the battery would necessarily be dead in the mornings.

Batteries are sensitive things inside.

Shorts inside a battery can come and go.....Only a new age battery tester can pick out problems inside a battery.
They put the battery though a series special tests.

You need to VERIFY once and for all the condition of this battery or you are just wasting time looking for the problem.

This battery may be good one moment and not another.... causing less than 8 volts to the igntion system causing the engine to stop running.

If your Heart stops...your body don't function.


It isn't " A Little thing.