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Alternator Problems, Again? Low charging voltage '03 7.3?

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Old 11-09-2010, 09:43 AM
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Alternator Problems, Again? Low charging voltage '03 7.3?

Fellas -

My 2003 Ex has had a few slow starts after it's been sitting for a while. Just turns over kind of slow and then cranks up. I live in Northern VA, so it's been getting colder lately.

Normally, I would think the batteries are going bad, but they are both 5 month old Motorcraft 100 month batteries with 850 cca. They also tested fine with a 500 amp load test. Resting voltage on both is right at 12V.

However, when I start up the truck, the voltage at both batteries is either 11.4V or 12.2V. Shouldn't this be higher? 13V or 14V? The alternator is a remanufactured unit that's I installed about a year ago.

About to take a long trip with it and don't want the alternator to crap out on me. Had that happen before and it's no fun. Guess I could carry a spare and swap on the road if I have to, but that's far from the preferred solution.

Any thoughts?

Thanks,

Scott
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Old 11-09-2010, 09:48 AM
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yep should be 13.8-14.2 when the gpr is off. sounds like you need a new alt. i just went thru some problems with my alt and had a local shop rebuild it and beef it up. a month later the diode in it took a dump. a month after that the regulator went out on it. im glad it has a lifetime warranty......
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Old 11-09-2010, 09:50 AM
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Originally Posted by bulletpruf View Post
Fellas -

My 2003 Ex has had a few slow starts after it's been sitting for a while. Just turns over kind of slow and then cranks up. I live in Northern VA, so it's been getting colder lately.

Normally, I would think the batteries are going bad, but they are both 5 month old Motorcraft 100 month batteries with 850 cca. They also tested fine with a 500 amp load test. Resting voltage on both is right at 12V.

However, when I start up the truck, the voltage at both batteries is either 11.4V or 12.2V. Shouldn't this be higher? 13V or 14V? The alternator is a remanufactured unit that's I installed about a year ago.

About to take a long trip with it and don't want the alternator to crap out on me. Had that happen before and it's no fun. Guess I could carry a spare and swap on the road if I have to, but that's far from the preferred solution.

Any thoughts?

Thanks,

Scott
When the engine is up and running, you should see over 13 VDC at the battery. However, cables and terminals in good condition are essentials and poor connections will certainly make for poor start-up and charging. To remove your concern about the alternator, why not run down to Advance or comparable and have em put a tester on it?

Carrying a spare alternator might be a bit extreme, in my opinion.

Steve
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Old 11-09-2010, 09:58 AM
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Originally Posted by indyF-350psd View Post
yep should be 13.8-14.2 when the gpr is off. sounds like you need a new alt. i just went thru some problems with my alt and had a local shop rebuild it and beef it up. a month later the diode in it took a dump. a month after that the regulator went out on it. im glad it has a lifetime warranty......
What is a GPR? Not familiar with that term.

Also, what alternator is that with a lifetime warranty? Guess I should check my receipts to see if mine has a warranty, too.

Thanks,

Scott
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Old 11-09-2010, 10:03 AM
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Originally Posted by RV_Tech View Post
When the engine is up and running, you should see over 13 VDC at the battery. However, cables and terminals in good condition are essentials and poor connections will certainly make for poor start-up and charging. To remove your concern about the alternator, why not run down to Advance or comparable and have em put a tester on it?

Carrying a spare alternator might be a bit extreme, in my opinion.

Steve
Steve -

Connection at the batteries are in good shape. I keep them clean with a light coat of grease. I guess I could check the connection at the starter, too, and check the grounds. Cables look fine. Are these trucks known for having problems with cables or connections?

I have another tester or two in the garage. I can double check the reading.

Thanks,

Scott
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Old 11-09-2010, 10:14 AM
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Originally Posted by bulletpruf View Post
Steve -

Connection at the batteries are in good shape. I keep them clean with a light coat of grease. I guess I could check the connection at the starter, too, and check the grounds. Cables look fine. Are these trucks known for having problems with cables or connections?

I have another tester or two in the garage. I can double check the reading.

Thanks,

Scott
I don't think there are particular problems, but I can't tell you how many times I see parts being replaced that don't solve the problem. I tend to emphasis diagnosis (perhaps at times too much) before replacing parts.

I think the key here is, once your engine is up and running, does the voltage on your meter at the batteries read over 13 volts. If you have good connections, it should. If not, I would suspect the alternator, but would not replace it without having it tested.

My thoughts,

Steve
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  #7  
Old 11-09-2010, 10:31 AM
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Quote:
Originally Posted by bulletpruf View Post
What is a GPR? Not familiar with that term.

Also, what alternator is that with a lifetime warranty? Guess I should check my receipts to see if mine has a warranty, too.

Thanks,

Scott
GPR = Glow Plug Relay. It energizes your glowplugs at start up. It can be up to two minutes after you first start the engine. (The GPR is working long after "wait to start" light on the dash goes out - a common misconception. FYI). If you are seeing 11 -12v at intial start up but the volts jump to 13.5 - 14v after the GPR stops working, then your alternator is working properly. If you look on top of the engine, behind the plastic Power Stroke vanity cover (if you still have it) there are two relays to the passenger side of the engine between the valve covers. The relay to the rear is the GPR.
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Old 11-09-2010, 10:37 AM
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I've solve a LOT of charging issues over the years by doing this on various vehicles.

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Old 11-09-2010, 10:42 AM
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Dan, I got to do this for mine. You just hooked up 4 gauge wire from the back of the alt to the positive post and then another one from the the mounting bolt to the neg post, right?
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Old 11-09-2010, 11:58 AM
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Quote:
Originally Posted by Ponyboychris View Post
GPR = Glow Plug Relay. It energizes your glowplugs at start up. It can be up to two minutes after you first start the engine. (The GPR is working long after "wait to start" light on the dash goes out - a common misconception. FYI). If you are seeing 11 -12v at intial start up but the volts jump to 13.5 - 14v after the GPR stops working, then your alternator is working properly. If you look on top of the engine, behind the plastic Power Stroke vanity cover (if you still have it) there are two relays to the passenger side of the engine between the valve covers. The relay to the rear is the GPR.
Thanks, Chris. I'll make sure the GPR is out before testing it again.

Scott
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Old 11-09-2010, 11:59 AM
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Originally Posted by RV_Tech View Post
I don't think there are particular problems, but I can't tell you how many times I see parts being replaced that don't solve the problem. I tend to emphasis diagnosis (perhaps at times too much) before replacing parts.

I think the key here is, once your engine is up and running, does the voltage on your meter at the batteries read over 13 volts. If you have good connections, it should. If not, I would suspect the alternator, but would not replace it without having it tested.

My thoughts,

Steve
Steve -

Understood. I'll get it checked at the local Advance or Napa before I swap it out.

Scott
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Old 11-09-2010, 12:03 PM
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Originally Posted by indyF-350psd View Post
yep should be 13.8-14.2 when the gpr is off. sounds like you need a new alt. i just went thru some problems with my alt and had a local shop rebuild it and beef it up. a month later the diode in it took a dump. a month after that the regulator went out on it. im glad it has a lifetime warranty......
Just found my receipt - I have a "Duralast Gold" alt from Auto Zone - set me back $201.99 new on 12/31/09. Looks like I'm headed to Auto Zone so they can test it and hook me up with a new one if it's bad.

Thanks,

Scott
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Old 11-09-2010, 01:05 PM
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When you checked your cables, did you remove both battery and ground cables to check the contact areas? The contact areas need to be clean down to shiny metal and then coated with dialectic (noalox) grease before you reassemble the cables. You might want to check the connection at the starter motor also while the battery cables are disconnected, a bad connection there will cause the same issues. The starter motors on our trucks tend to want to loosen the bolts holding the starter in, so you might want to check the bolts for tightness as well.
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Old 11-09-2010, 03:05 PM
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Quote:
Originally Posted by Ponyboychris View Post
Dan, I got to do this for mine. You just hooked up 4 gauge wire from the back of the alt to the positive post and then another one from the the mounting bolt to the neg post, right?
Exactly, just piggyback the existing wiring harness.
Before you install the wiring, check the charge rate at the battery, then check it after.
And make a mental note of where the voltmeter sits in the cab as well.
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Old 11-09-2010, 03:21 PM
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Will do, Dan. I have an Autometer voltmeter gauge so I'll check it out.
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