Thorough Alternator Diagnosis

[JRA2000TL]

I just swapped my AZ reman alternator last night under warranty because I had the following issues:

1. Battery bought 11/10, charges up, tests good on my charger and AZ's.
2. Checked battery posts while the car was idling under a full load; voltage drops from 12.7 gradually downward very slow.
3. Made sure battery terminals were tight on battery, also verified that the lead (metal eyelet thing) on the back of the alternator was secured to the stud on the alternator itself.
4. Did a test I read about online where I disconnected the negative battery cable, put 1 voltmeter probe on the positive battery post and put the other on the rear stud of the alternator. Set meter to ohms and got a bunch of #s jumping around, went OL then 40-50 then .5 to 1, etc. I was told this is to check your fusible link. Results were inconclusive based on this erratic reading.

Both my old alternator and this new reman out of the box pass AZ's test. Both say "fault" on my battery charger when I test them while the car is running.

I get no battery light on the instrument cluster.

What else do I check? Where is the fuisble link and how can I check my wiring otherwise? I've gone as far as I know what to do. AZ told me if this one doesn't fix it that I need to address my wiring before they warranty out another one.

I'm tempted to take a $55 gamble and buy a used OEM one currently on Ebay just for the **** of it to see if it works since it's a Motorcraft and not AZ reman crap.

 

[jelloslug]

Buy a good used one. I went through 4 Napa Gold alternators before I gave up and bought a good used one. It's been fine since 2004.

 

[luigisho]

AZ bench test pass won't guarantee it will do the job. However, if it fails the bench test it will stop you from going further.

 

[LOUDSHO92]

We do offer new and rebuilt alternators and they are not A1 units. Check it out: SHO Source

 

[JRA2000TL]

Called the store and had them order 1 more. This is the final shot. I told them I checked all the wiring and the connections. I have new battery terminals on there and the car was running fine until a couple of weeks ago. I told them I checked the resistance on the lead wire on the back as well and that the thing just won't charge regardless of what their test says.

If this one doesn't work, I'm getting a refund and buying a used Motorcraft from someone on the forum if they have one. The Motorcraft remans are like $300.

 

[kevinspann]

$300? You could buy a whole car for that.

 

[SHOhopefull]

 

[kevinspann]

Yes you did, so here is a reward

Jeremy, if it is dropping FROM 12.7, it's not charging anyways. Does the battery light work?

 

[JRA2000TL]

Battery light works because 2 alternators ago, that's how I knew the 1st Delco one went bad. I will turn the key to ON this afternoon and make sure it still lights up though.

 

[SHO1]

Take it to a diff auto store or rebuild shop for the heck of it and see if tests same there.

 

[Bob Gervais]

Take it to a diff auto store or rebuild shop for the heck of it and see if tests same there.

^this, if for nothing more than proof that it's junk.

 

[SHO1]

Yep, that and it would be interesting to know if a tester other than AZ says good or bad.

 

[SHOtimer]

I was always told that disconnecting the cable like that when the car is running can eff up the PCM....

Doug

 

[itwonder]

Did you test the two little leads? One of them comes from the ignition switch, and feeds 12 V to activate the internal voltage regulator. The other lead comes from the negative side of the alternator lamp. The voltage regulator grounds it to turn the light on. To test them, pull the connector and connect a test light between ground and each pin, with the ignition switch on. The ignition lead should illuminate the test lamp. The other lead should illuminate the test lamp and also cause the alternator light to illuminate, dimmer than normal. An LED test light doesn't draw enough current for this test; use an incandescent one.

If voltages on the the little leads check out, the other test you can do is make a jumper wire to go between the B+ terminal and the battery positive terminal. This bypasses the fuseable links etc.

If the alternator is working, you should read 13.5-14.5 VDC at the battery terminals, when the car is running.