Alternator, bad? Definitive test?

dodge
ram50

#1

I’ve either a battery problem, or an alternator problem ( I guess). [ The vehicle is a 1990 Dodge Ram 50 - 2.4L engine ]

I drive the truck around for a couple of days and eventually the battery gets to the point where I have to recharge it. Then it’s fine for another couple of days and then the cycle begins again. (Battery is about a year old, give or take.)

Of course a friend told me to start the truck and then remove the positive connection to the battery. He said if the engine then conks out, the problem is the alternator. It did conk out. My question is: how definitive is that test?

I’ll be reading everything on this forum having to do with “alternator.” And I’m watching a couple of YouTube vids in order to learn how to diagnose this problem with a multi-meter.

Thanks!!


#2

Go down and buy yourself one of those plug in battery, charging system readers for $15 or so. They plug into the accessory outlet. Key on before you start should read somewhere around 12.4 volts, start the engine and it will show the rate of charge from the alternator. 13+ volts. It’ll give you a red light, amber, or green. Pretty simple and you can do it while driving. I keep one in each car since they don’t put in volt meters anymore, and plug it in once in a while just to check.


#3

Whoever told you to disconnect the battery cable while the engine is running is NOT your friend.

That’s an excellent way to fry the electronics in the vehicle.

http://www.troubleshooters.com/dont_disconnect_battery.htm

Most local parts stores will test your battery/charging system for free. So try that first.

Tester


#4

You can bring your battery to almost any auto parts store that have battery testers that will check it for free by discharging and recharging the battery. Once the battery is ruled out, you can always bring it to a place where they rebuild alternators and they’ll check it properly for free as well. They can also determine if you need a regulator replacement of it the whole thing needs a rebuild.

It does sound like your alternator though since it’s what keeps your car running after it’s started. The battery is just to turn it over and if the alternator can’t produce enough power, it’ll drain the battery.


#5

The alternator rebuild place for testing is only if your knowledgeable on how to remove the alternator and give it to them to test on a bench with a dummy load. I’ve heard testing it in the vehicle isn’t the best method, but I’m no expert in that area.


#6

Not to be a curmudgeon but take what those store testers say with a grain of salt. Maybe for a quick test if its completely dead. I had a Napa alternator that would fluctuate. It was still under the warranty but of course it tested good but the voltage would fluctuate to drive you nuts at night. I just said to heck with them and bought a new Delco alternator instead and never went back for alternators anyway.

Recently bought a new lawn mower battery and after adding the acid, it heated up pretty good. Put the charger on after the instructed wait period and could never get more than 160 CCA out of a rated 275 battery. Took it back for a replacement but they said it tested good. They still exchanged it and the new battery not only did not heat up after adding acid but tested well over 300 CCA after charging and sitting over night. So just saying, you need to be able to help yourself a little sometimes and not just rely on the testers at the stores. Unless maybe you’re a pro and have a reliable guy you deal with.


#7

Just bought one from Amazon. Great suggestion, and thank you!


#8

I would buy a multimeter you can test the voltage with it that’s what I did less than a month ago here’s a link to a good video on testing an alternator https://www.youtube.com/watch?v=LGB6ZEjGm7Q


#9

Is the alternator belt in good condition, and appropriately tight?


#10

Well, OK. I won’t do that again! And I should have explained that I live fifty-five miles from the nearest town, which makes testing this stuff a bit difficult. I think I pretty much have to figure this out without the help of a parts store or mechanic. Unfortunately.

But Thank you!! for taking the time to respond.


#11

Did that truck come with a battery (alternator) gauge in the dash cluster? If so, it should rest a little below half with engine off, a little above half with engine on. Did you ever pay attention to where it was when working properly (don’t feel bad if not); and how is it now? Might be a quick clue before your tester arrives.


#12

I should have explained that I live fifty-five miles from the nearest town, which make testing this stuff a bit difficult. I think I pretty much have to figure this out without the help of a parts store or mechanic. Nice hear someone else who thinks the problem is the alternator. :relaxed:


#13

Here’s a picture of the dash, it’s a compact Mitsubishi pickup sold as a Dodge (edit - is this more like it?):


#14

Well I’m certainly not a pro.

I should have explained that I live fifty-five miles from the nearest town, which make testing this stuff a bit difficult. I think I pretty much have to figure this out without the help of a parts store or mechanic.

Thanks for ‘the word’ on the testers stuff! Much appreciated!


#15

That’s the one I’ve been watching. I did the procedure yesterday and it seemed to indicate the alt wasn’t charging the battery too well. Great video. Thanks for pointing it out and taking the time to try and help!


#16

Seems to be. Thanks for the input!


#17

No problem also if the battery is only a year old then it should still be good depends as long as it’s not a crap brand. When I got this car a month ago I wasn’t sure if the battery could come back it only had around 4 volts I filled it up with distilled water because it was pretty low and charged it and it works like new but it also was only like 8 months old. The car had a bad alternator as well.


#18

That is an Omni/Horizon instrument cluster. I believe the Mighty Max has a warning light, no gauge.


#19

I haven’t even noticed it. I’l be making a short tip in about two hours: I’ll keep an eye on it. Great suggestion! and thanks for taking the time to try and help out.


#20

All I have are idiot lights. :slight_smile: Thanks!