2003 7.3.....Alternator problems
 

Ok...I am going to copy my posts from another forum and see if anyone here can help me.

In the last 5 years I have put 4 alternators on my truck. Original alt. lasted 5 or 6 years then went bad. I replaced it with a Kragen brand, it went bad with-in a couple months. Someone mentioned stay away from them. So I got a NAPA alt. and it went bad with-in a few months. NAPA suggested to put a motorcraft alt on, so I did threw NAPA. The motorcraft alt. lasted 2 months shy of two years. Good thing it had a two year warr. I replaced it with another Motorcraft alt. The alt. is charging but the battery light is still on.

Yes the wires are installed right.

Someone mentioned these year alt's. have problems with the built in regulator?

Could someone tell me what is going on? Why do I keep loosing alt's.? Why is my alt. charging and light still on.


The alternators were working for a few months, when I noticed the battery light come on I checked it with my volt meter to see if it was working. The alternator I have now shows it charging but the battery light is still on. I have had this alt. on sence Aug. The light came on not long after replacing the alt. So far as the batteries, My truck starts up normal as if the batteries were fully charged. I guess I could or should have them load tested.
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The alternators that I replaced were definitely bad.

The first thing I check when I have a battery go dead is the alternator.

Anyways, I disconnected both batteries to see how many volts were in each, both 12 volts.

Next step...Load test each battery

I will let everyone know the outcome as soon as I do it. It might be a couple days. I live out in the country and sometimes work long days. So I will do it when I can.


Ok.....I went and had my batteries tested, both were fine. One the cranking amps were a little lower than the other. (old batteries were dated 05/06).

So I decided to replace them both anyways. (new ones dated 01/12)

Battery light is still on.

With the truck running (old and new batteries) the alt. is putting out 14.2 volts (seems a little high). The two wires coming out of the back of the alternator connector is at 12.2 volts running or turned off.

I am thinking replace the alternator.....anymore suggestions.


Ok......I just went and played with it a little more. I check for dirty wires etc. I cleaned them all up. I decided to pull the wire connector with the two wires off the back of the alternator. With the connector unpluged I crossed the wires with a volt meter, it read 12.2 I then started the truck up with the connector unpluged the batt. light was off. I pluged the connector back into the alt. and the light came back on.

I thought this should be opposite.....pluged in light off.....unpluged light on


tenpack, Could you tell me how to do a voltage drop on the output wire. I ran the volt meter from the big wire to the battery. It was putting out 14.2 volts




So....The battery light is on.

I have two new batteries. I am charging at both batteries 14.2v. All connections are clean.

Why is my battery light still on?
One thing I didnt mention is my alternator gets real hot to the touch.

These trucks are tough on alternators. When the truck first starts, the glow plugs are all on and the batteries need to recover. In the 5 years I've had my truck, I've had to put two alternators on. You do seem to be going through yours rather quickly, however.

The voltage drop test is a good check. You are looking for the difference in voltage from one end to the other. Starting with the meter hooked to the battery, take a reading with it running. Move the positive test lead to the back of the alternator and take a reading. it should be a little higher at the back of the alternator, do this for both batteries.

I would have to look at the wiring diagram to see if the alt is turned on by the PCM. I would say that your replacement alternator just has a bad regulator. I would make sure it's definitely for the 7.3 because i think the 6.0 one will bolt in but has a different regulator. The light goes out when you unplug it because the alternator supplies ground through the regulator when the alternator is off, and 12+ when it's running. So it doesn't see the ground through that wire and doesn't turn on the light.

add a extra negative wire/lead from starter to engine block
I had similar issues with my 02 and going through 3-4 alts in 5 years and starters

Well here is the outcome

After checking every possible thing testing wires, cleaning cables, replacing both batteries and battery light still being on. I decided it had to be something in the alternator.

So, I went and and got a new (rebuilt) alternator (old on was still under warranty) and BAM!!!!!!! battery light is no longer on. Problem solved.

So we know it was the alternator but do we know what about the alternator caused this? What do the little wires on the back of the alternator do. I just just put a re-manufactured alternator on my truck and now the light is on all the time too.

I'm having a similar issue going through alternators. I've owned my 2000 f250 for about 3 1/2 years and have put 5 alternators in it. I just installed the 5th today so thought I'd search and see if anyone else has this issue. Bought the first three at advanced auto and they only lasted a couple months. The last two are from napa and lasted about a year or so. Doesn't make sense to me that I'd be running through alternators like this. If anyone figures this out please let us know. :-banghead

I have an e99. I got it in fall 05. I put the first alternator in winter of 07/08. I went with an upgraded 200A 6G small case. This lasted me about 3.5 yrs. So I got a 200A 6G Large case Oct 2011. Its not charging when cold. Once warmed up it seems ok, but I know this is the beginning of the end. Yes.....batteries are good quality within a year. Ground to the starter. Extra positive fused cable from the alternator to the drivers side batt. Seems my truck doesnt eat them as much as others, but any info would be welcome. I'm gonna order a new voltage regulator.

Subscribing....

My truck loves alternators......two from autozone with lifetime warranties, and three from napa. Most only last 9-12 months. Batteries are new, cables are newer, still the same problem.

I just replaced the alternator on my 2000 7.3 about a week ago for the first time. Now the SES light is coming on and the idle is frequently rough. It has also died on me a few times.

Any ideas what might be causing this and a fix?

Thanks.

i had this problem with my 2003 mustang light would come on so often then stay on at times wouldnt start, got new alt same issue

When the shop gave me my Alt that I had them rebuild, they originally put in a regulator from an ambulance package. Seem to work ok but the Battery light was on. Took it back and they put the right one in and it works fine now.

The "ambulance package" is the dual alternator package. The top alternator acts just like the single alternator, regulator-wise.

The second alternator's regulator requires an outside input to begin producing current, and that signal comes from the Powertrain Control Module (PCM) when it senses lower-than-normal voltages to the battery.

That shop must have put in a regulator from a secondary alternator to begin with.

It's a different "color-code", and ours should be grey-on-grey.

Pop

You right it was a different color. The new one is a grey color.

I knows most'a me 6G's.

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Yuk yuk yuk yuk yuk...... :)

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