Alternator?

[BrockGrimes]

How do you test an alternator while it's in the jeep for proper operation?
To make sure it's putting out the right voltage and not over charging the battery.

Should be what 14v or something like that? Is it constant?
I swapped in a 124amp CS144 from a caddy and I know I had issues with the old battery but I want to eleminate the alternator as the cause.
Especially since I just picked up a Red top optima. $145

 

[CJ]

Ah - electricity... One of my favorite subjects...

Do these tests with the heater motor running or the headlights on or even both. You need a load on the system.

1) At idle most alternators put out between 13.7 to 14.2 volts. Now, depending on how accurate your meter is or what the ambient temperature is your voltage may vary.

2) Next, go to about 1500 - 2000 RPM and check your voltage. Should be about 14.4 volts - give or take about .2 or so.

3) Turn off the heater or the lights and keep the engine at high idle. Make sure you never go above about 14.8 volts.

A quick test for charging is to place the tip of a screw driver to the back of an alternator on the bearing cap and see if it sticks... The alternator should be creating a magnetic field if it is working.

 

[dalefan88]

or take it to advance auto and get checked for free. lol had to put that in for my work. what cj said is the best for at home that is basically what we do at work with the new outside tester.

 

[PinkBlackAndMud]

I just had some of the same problems with mine. I took mine to Auto Zone and they tested mine for free. Although i knew mine was bad, but i have another one from an older Pontiac and wasn't sure if it was working right. For once my luck was good!

 

[projectcrawler]

Another quick test is basically what CJ said, but do it with the - terminal disconnected from the battery. If you disconnect the battery with the jeep running, headlights and blower on, and the jeep shuts off, it isn't charging well. Keep an eye on voltage just as CJ said to check for overcharging. Some people don't like this test because they say it can spike an electrical system and cause problems. I have been a flat rate tech for over a decade, and I have never even heard a story where anything fried from doing this test.

 

[CJ]

I almost added that little test in my post but didn't... As you said, if the thing keeps running, it's charging.

As you stated, on most vehicles this will never cause a problem. Our Jeeps are pretty sturdy hunks of iron and I have done this when I needed to start a vehicle that the battery was shorted out on...

BUT - Be careful with some new vehicles. On my old GF's Honda - the manual clearly stated 'never' disconnect the battery while it was running... Will it blow up or maybe pop a diode? Hell if I know... That was just the Jeep-CJ.com disclaimer!!! :laugh:

 

[BrockGrimes]

Well i had it checked at autozone, they said it's putting out 14+v but it's only putting out 10amps.......WTF?
Even rev'd it up. Weird only 10 amps, I had it checked twice at autozone before installing it. Volt guage in the jeep reads 12v and ticks to 14 or stays over at 16v.

 

[projectcrawler]

I am unfamiliar with autozones test, do they do it in car, or bench test it? If it is in car, you may just have some corroded connections or wires. Resistance=bad.

 

[CJ]

To accurately check output amps you have to measure the load on the alternator by placing a measuring circuit inline. The only other way is by a clamp on meter. All amp meters have to placed inline to absorb the full load.

 

[Ggg]

AZ does not have the ability to load test an alternator, AFAIK.
My CJ2a has a 68 225 V6 in it and the newer alt/starter test machines can't test my alternator because they must find the application in the machine's computer.
I personally would not do the battery disconnect test on any computer controlled car. But on something as old as my CJ, sure all the time. But thats just me.

 

[CJ]

My CJ2a has a 68 225 V6 in it and the newer alt/starter test machines can't test my alternator because they must find the application in the machine's computer.

That is such a bunch of . It's a damn alternator! Not a jet engine. What happened to using a little bit of brain power and either substituting something similar or even just doing a manual test...

Jeez!

 

[dalefan88]

go to advance auto. we dont need any info to test a starter. inside or outside. if they check the alt outside, they need the clamp on to do the test right. inside they probally can use the universal connecter.

 

[BrockGrimes]

They tested it while it was in the jeep, hence the mention of reving it up.
I didn't pay attention to the connectors he hooked up when testing, but he was a 4x4 guy and was the manager.
I swapped the old jeep alt back in and will have the caddy alt retested, this time by advance and maybe checker too.

 

[Ggg]

CJ I agree the new computerized test machine sucks. They can't just do a generic test, they need vehicle info for the machine to even spin the alternator. Believe me I am not knocking the parts guy he is a good guy but the machine is what it is.
I run into the same issues buying other parts for the Willys. I tell them do not waste your time looking in the computer, just get the books out and start there.

 

[CJ]

I run into the same issues buying other parts for the Willys. I tell them do not waste your time looking in the computer, just get the books out and start there.

I too run into this all the time. I'll walk in an tell them I need a certain bearing or a certain belt that I have put on the CJ.

I'll get the typical question of what vehicle. I'll tell them - don't worry about it, cross the bearing # for one you stock and I'll take it. Sorry, can't do that. Then after entering all the info in the computer, I'm told it won't work or there is no listing... I then tell them, that is why I gave you the number - it's what I know works!

Napa is the best at getting parts, most of the time I just walk in, say I need this # and they get it.

Most of our parts stores here in my little town are great though. I never have a problem with Autozone, Adavnce or Oreily. Seems they have good, knowledgeable people working there that understand what it's like to work on a 37 year old truck. It's the people in 'the big city' I always have trouble with. You know, the ones with the clean fingernails...

 

[BrockGrimes]

I used a multimeter and tested the voltage the stock alt is putting out 16V at idle.
Is this the norm?

 

[CJ]

That's pretty high. Sounds like a bad voltage regulator. At idle you should never see more then about 14.8v

 

[coldwater]

Napa is the best at getting parts, most of the time I just walk in, say I need this # and they get it.


I never have a problem with Autozone, Adavnce

That's the diference between going to a parts joint that mechanics use, and one that sells trinkets to people pay to have their cars waxed for them. My local NAPA guy is the BOMB! been behind the counter for 25 years and knows the routine. Karl, I need this. ......yup, lets see what we got. Advance, or Autozone is a disaster here! If it aint in the puter, it don't exist. OR.. that's not what the puter says, won't work.
JUST GIMMIE THE PART!!!!!!!!!!

 

[CJ]

I believe it all comes down to location and training...

In our small farm town, many work on their own vehicles so all our parts stores are very good. I'm not knocking Autozone, Advanced or Oreily...

Heck DaleFan88 works there (Autozone) and we all know that he works on and understands vehicles...

Any parts store can be great if the right people are put in place. Napa just tends to cater to the professional mechanic so they tend to have the more experienced people in place. Of course Napa is usually a bit more expensive but you pay for that experience.

The other stores have a much less experienced clientell so they have to have the safe guards in place to filter out all the wrong information. If they didn't - they would be handleing returns all day long!

Not everyone who goes in to a parts store can look at a brake shoe and know if its the leading ot the trailing one... Just us Jeep people! :laugh:

 

[projectcrawler]

I have an ace in the hole. My father-in-law works for federated auto parts. He is a car guy, and has about 30 years working for parts suppliers. We do pick on him because he worked for a company that federated bought out. The company was called Manlove auto parts. He has a company truck that he drives home and it says Manlove all over it.