Alternator going bad maybe, or glow plug module? - F-Series & SuperDuty Diesel Forums

mudking82 · 07-02-2009, 01:37 AM

I have been lurking for a while, but finally decided to join. There is lots of great information here. This is my first diesel, and I love it! But here is my recent problem. I have searched extensively for a similar problem, but have not been able to find one. This is in regard to the truck in my signature.

Sometimes after I have been running the truck for a while, it will stop charging, or not start charging again after I restart it. On the first start of the day, it will charge normally for quite a while. Example: I start the truck, and once the glow plugs shut off, it will charge at around 13.8-14.2 volts, and be putting out at idle with no load 35-38 amps, or with a load at idle be putting out 65-70 amps. After driving for about ten minutes, my digital in cab volt gauge starts to go down, like about a tenth of an amp every five minutes, until it gets to around 13.6 while driving with no loads on.

Then here is where the problem comes in. Usually it happens after about 3-5 starting cycles and a total of around 30 minutes of driving. I will start it up, and it will never start charging, as if the glow plugs are not shutting off to allow it to charge. When this happens I only have 12.6 volts and below at the batteries, and alternator is only putting out from 2-15 amps while this is happening with no loads on. Seems to start working fine again if I shut it down and let it sit for a bit, as if it is related to temperature. Also when this happens the battery light comes on in the cluster. Sometimes after 5-10 minutes it will start working normal again while driving, other times it has to sit for a while. Can't figure out a certain pattern of it yet.

Especially after it has been sitting a while, such as on the first start of the day, the alternator seems to work perfectly fine. It varies the amps depending on load and battery state of charge. While it was working normal I tested it with a Midtronics tester and the charging system tested fine. But then when it warmed up and quit working right, it didn't test good, as there was "no diode ripple detected". Does this sound like the alternator going out, or could the glow plug control module be causing this weirdness?

Please give any thoughts, suggestions, tests, etc. I used to be a mechanic so I have plenty of tools to check stuff, so don't be afraid to point me in the direction of performing some test on it. Thanks in advance for any help!

Zookie400 · 07-02-2009, 08:32 AM

it sounds like an alternator going bad.

if the GP's were staying on, there would just be more draw and the alternator should be kicking 100+ amps at high idle under a maximum draw situation.

mudking82 · 07-02-2009, 10:19 AM

Quote:

Originally Posted by Zookie400

it sounds like an alternator going bad.

if the GP's were staying on, there would just be more draw and the alternator should be kicking 100+ amps at high idle under a maximum draw situation.

But I didn't think that the alternator will charge unless the glow plugs are off?

DaveBen · 07-02-2009, 10:32 AM

The glow plug controllers, on these trucks, are not known to go out.

Dave

snicklas · 07-02-2009, 11:56 AM

Quote:

Originally Posted by Zookie400

it sounds like an alternator going bad.

if the GP's were staying on, there would just be more draw and the alternator should be kicking 100+ amps at high idle under a maximum draw situation.

X2. I had a similar problem and it was the alternator. If my truck was driven around town and started and shut down alot, it would not start the next morning. If I put a float charger on it , it would be fine. Replaced the alternator and problem solved. One thing to be prepared for is the cost...... A replacement will be arounf $200. Also, when you change it out, leave the belt on the rest of the engine and remove the alt. and support the belt with a bungee cord to the hood. It is a MAJOR PITA to put the belt back on one of these trucks...... My dad and I changed it out and we just eased the alt out from under the belt, and on replacement, pulled the belt slack as best we could and replaced the bolts. Make sure to take off the little top shield on the fan shroud to have better access. Insert a small flatblade screwdriver beside the retaining "bump" and gently pry the bottom of the small shroud toward the front of the truck at each "bump" to release the small shroud. Also, when you take off the small push on connector on the back of the alt, you have to squeeze the release "just right" to get it it pop off.

mudking82 · 07-02-2009, 08:14 PM

Thanks a lot for the replies. So is it just a matter of time before it quits completely?

Friis · 07-03-2009, 06:12 AM

Quote:

Originally Posted by mudking82

Thanks a lot for the replies. So is it just a matter of time before it quits completely?

It was in my case. I experienced similar symptoms as you, but I was sometimes able to get the alt charging again with a gentle whack with a hammer.

Eventually though it gave out completely, and I changed the alternator. Runnning perfectly since.

07-02-2009, 01:37 AM	#1
mudking82 SDD Junior Member Join Date: May 2009 Location: CA Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	Alternator going bad maybe, or glow plug module? I have been lurking for a while, but finally decided to join. There is lots of great information here. This is my first diesel, and I love it! But here is my recent problem. I have searched extensively for a similar problem, but have not been able to find one. This is in regard to the truck in my signature. Sometimes after I have been running the truck for a while, it will stop charging, or not start charging again after I restart it. On the first start of the day, it will charge normally for quite a while. Example: I start the truck, and once the glow plugs shut off, it will charge at around 13.8-14.2 volts, and be putting out at idle with no load 35-38 amps, or with a load at idle be putting out 65-70 amps. After driving for about ten minutes, my digital in cab volt gauge starts to go down, like about a tenth of an amp every five minutes, until it gets to around 13.6 while driving with no loads on. Then here is where the problem comes in. Usually it happens after about 3-5 starting cycles and a total of around 30 minutes of driving. I will start it up, and it will never start charging, as if the glow plugs are not shutting off to allow it to charge. When this happens I only have 12.6 volts and below at the batteries, and alternator is only putting out from 2-15 amps while this is happening with no loads on. Seems to start working fine again if I shut it down and let it sit for a bit, as if it is related to temperature. Also when this happens the battery light comes on in the cluster. Sometimes after 5-10 minutes it will start working normal again while driving, other times it has to sit for a while. Can't figure out a certain pattern of it yet. Especially after it has been sitting a while, such as on the first start of the day, the alternator seems to work perfectly fine. It varies the amps depending on load and battery state of charge. While it was working normal I tested it with a Midtronics tester and the charging system tested fine. But then when it warmed up and quit working right, it didn't test good, as there was "no diode ripple detected". Does this sound like the alternator going out, or could the glow plug control module be causing this weirdness? Please give any thoughts, suggestions, tests, etc. I used to be a mechanic so I have plenty of tools to check stuff, so don't be afraid to point me in the direction of performing some test on it. Thanks in advance for any help! __________________ 2005 F350 6.0L 4x4 w/40,000 miles

07-02-2009, 08:32 AM	#2
Zookie400 I WANNA GO FAST Join Date: Mar 2007 Location: wallingford, CT Posts: 1,663 Thanks: 12 Thanked 45 Times in 39 Posts	it sounds like an alternator going bad. if the GP's were staying on, there would just be more draw and the alternator should be kicking 100+ amps at high idle under a maximum draw situation. __________________ There is a replacement for displacement, its called volumetric efficiency. THE MILLENIUM ZOOKWAGON: 97 F-350 4x4 85 BRONCO, 01 MUSTANG GT, 03 SUZUKI LTZ 400, 82 YAMAHA XJ750 SECA MY YOUTUBE VIDEOS!

07-02-2009, 10:32 AM	#4
DaveBen SDD Senior Member Join Date: May 2005 Location: Ukiah, California Posts: 7,596 Thanks: 106 Thanked 459 Times in 445 Posts	The glow plug controllers, on these trucks, are not known to go out. Dave __________________ 2004 F-350 Regular cab with 6.0, Torqshift, 4X4, and just about all of the rest of the options. I added Guages, Satellite Radio, Air Horns, and a coolant filter. Bilstein shocks. Battery Desulphater that really works. Installed Jimmi Jammers. Pictures here: http://community.webshots.com/user/dbennett48 Completely Stock. I had a Detroit Diesel 8V92TA in a KW dump truck in 1980. That sucker would put out 425 hp but would never out pull a CAT.

07-02-2009, 08:14 PM	#6
mudking82 SDD Junior Member Join Date: May 2009 Location: CA Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks a lot for the replies. So is it just a matter of time before it quits completely? __________________ 2005 F350 6.0L 4x4 w/40,000 miles

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