Alternator Question

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CappyKD

CappyKD

10 Year 15 Year
Joined
May 16, 2007
Threads
22
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1,517
Location
SoCal
I have noticed that on my 100, that my alternator seems to do a better job when cold. 14.3 volts via the odb-II port in the morning at high idle. Once warm/hot the most I see is 13.4-13.5 volts at any rpm. If I am idling in traffic the volts drop into the low to mid 12's.

I'm pretty sure the voltage regulator in the alternator is going out. Thoughts?

I'm going to end up replacing the alternator with a mean green 200 amp model. I will upgrade the charging cable as part of that install. I'm just wondering if I need to replace the alternator sooner rather than later. Opinions?

Thanks,
 
Reading voltage without reading the current only gives you half the picture. 13.4 volts at idle is meaningless. 13.4 volts at 125 amp at 2,000 RPM is fine. 12.7 volts at 180 amps is fine too. You also have to check the resistance between the alternator output post and the actual battery positive post. Short answer is....not enough information to make an informed decision on the Mean Green.
 
Thanks a lot for the reply. My concern is not so much whether the alternator is delivering full amperage , it is rather why the voltage drop. With bad bumper to bumper, hour plus grid lock on really hot days I have seen voltage in the 11's at dusk with the lights on. Thats almost low enought to shutoff an arb fridge and keep my dual battery system both of which are voltage measured from functioning. I have a oem hand throttle to get around the fact that the alternator needs to spin a bit to start making amperage when camping, but my daily commute sometimes worries me.

Thanks again for the reply.
 
Where are you getting the voltage reading from? My scanguage reads about .5 ot .75 volts lower than the voltage at the actual battery post presumably due to resistance in the electrical system wherever the OBDII reads voltage and will expect that to get worse with age.

Scott
 
mobi-arc said:
Where are you getting the voltage reading from? My scanguage reads about .5 ot .75 volts lower than the voltage at the actual battery post presumably due to resistance in the electrical system wherever the OBDII reads voltage and will expect that to get worse with age.

Scott
Click to expand...

Thanks for the reply Scott.

I am getting it from ODB-II, however I am still trying to understand why I have more than a full 1 volt drop from cold to hot, both are read from the same place so unless the resistance is heat related, I wouldn't think that where I am reading from explains the readings. This morning i was at 14.1 volts for the first 15 minutes of driving with the lights on. After driving in bumper to bumper for about 30 mins, or 45 minutes of total driving, I saw 11.9 at idle in gear, both readings were taken from the same place. Thoughts?

Thanks,
Kirk
 
Resistance is heat related. When battery(s)/alternators/cabling is cool, it is more efficient. As components heat up, they become more resistive. How many miles are on the alternator? Maybe the carbon brushes are not making great contact with the sliprings of the rotor. Maybe you have a high resistance joint that becomes evident at temperature. Maybe the regulator is behaving goofy. No way to pinpoint it without doing some probing.


CappyKD said:
Thanks for the reply Scott.

I am getting it from ODB-II, however I am still trying to understand why I have more than a full 1 volt drop from cold to hot, both are read from the same place so unless the resistance is heat related, I wouldn't think that where I am reading from explains the readings. This morning i was at 14.1 volts for the first 15 minutes of driving with the lights on. After driving in bumper to bumper for about 30 mins, or 45 minutes of total driving, I saw 11.9 at idle in gear, both readings were taken from the same place. Thoughts?

Thanks,
Kirk
Click to expand...
 
I am going to do some measurements on the wiring this weekend, but I am ordering a high idle output alternator from www.dcpowerinc.com they are local to me with a good warranty and what seems to be a great product line. I am going with the 180amp model. When I install it I will replace the charge lead with some 2/0 I have laying around. My alternator may be ok, but since I am doing the 100k plus full pulleys, idlers, fan bracket, fan clutch with fluid mod and a new OEM radiator, I might as well do the alternator when it's all apart. Check out the specs on their alternators. I like that they give all specs as opposed to mean green. Thoughts?
 
CappyKD said:
I am going to do some measurements on the wiring this weekend, but I am ordering a high idle output alternator from www.dcpowerinc.com they are local to me with a good warranty and what seems to be a great product line. I am going with the 180amp model. When I install it I will replace the charge lead with some 2/0 I have laying around. My alternator may be ok, but since I am doing the 100k plus full pulleys, idlers, fan bracket, fan clutch with fluid mod and a new OEM radiator, I might as well do the alternator when it's all apart. Check out the specs on their alternators. I like that they give all specs as opposed to mean green. Thoughts?
Click to expand...

I understand they do good work.
 
spressomon said:
Battery?
Click to expand...


Possible, but doubtful. It's a 6 month old Die Hard platinum Marine G31. And I charge it with the correct DHP charger every few months.

Thanks for the input Dan.
 
Kirk,
Your HO alt choice is one I've had on my back-burner for awhile. Anxious to hear your review once you've got it installed and have some use on it. Thanks for taking the lead dog position on this :D
 
spressomon said:
Kirk,
Your HO alt choice is one I've had on my back-burner for awhile. Anxious to hear your review once you've got it installed and have some on it. Thanks for taking the lead dog position on this :D
Click to expand...

Glad to try to help everyone else here. So I went to DCPOWER today and met the owner and he took me for a tour of his shop. Awesome guy, makes a great product as far as I can tell, specializes in military and other specialty applications. He has alternators for darn near any application, including the 100 series, 80 series 3.4L 5uz and even the 4.5 TD LC's. He sells a lot for mil. spec applications in the middle east. He also supplied the alternator for a Baja 1000 class winner (Forget the name and class.) I will post up a few pics inna few. Read the FAQ's on his website. They use all DENSO internals with custome cases pulleys and a few other bits, hand assembled and tested with a 400 amp loadbank alternator test station. I can't wait until mine is built tested and ready for pickup!
 
The only reservation I had with them was regarding my need for an external regulator. They wanted $150 more just to build the alternator without an internal regulator...with the cost of a fixed output regulator on top of that IIRC. And at least a month to do it...

I like the fact they service and/or order the bearings using high temp mil-spec type grease...and ample amount of it too. With our low slung alternators every little bit helps.
 
spressomon said:
The only reservation I had with them was regarding my need for an external regulator. They wanted $150 more just to build the alternator without an internal regulator...with the cost of a fixed output regulator on top of that IIRC. And at least a month to do it...

I like the fact they service and/or order the bearings using high temp mil-spec type grease...and ample amount of it too. With our low slung alternators every little bit helps.
Click to expand...

Dan,

Did you call them? Call them and talk to Dave (The Owner) or Andrew. The leadtime for mine is 1-2 weeks even though it says 3-4 on the website. I went in today and ordered the XP series for my 100 and a 180 amper for my friends 99 4runner. The 180 amp one will be ready in a week and the xp for my hundy will be closer to 2 weeks.

If you call tell them Kirk DeCarlo told you to call. I told them I was posting up a full write up on mud and that if everything works out, I'm sure they will get additional business from fellow mud and Yotatech (from my buddies 4runner) members. I'm so glad me and my buddy found them instead of me settling for a mean green. (publishes no specs.)

If you don't mind my asking, why the need for an external regulator?


Kirk
 
KlausVanWinkle said:
To your original question, Could it be because the idle is higher when you first start up the truck then once it reaches operating temperature? Have you factored in the GPH to make sure it's the same when the voltages are different?
Click to expand...

I have, but the drop is still there. My numbers are comparing warmed up to heat soaked, not much of an rpm difference but quite the drop in voltage.

Thanks for the reply!
 
A few pics.

20130905_150200.webp


20130905_150148.webp


20130905_150153.webp
 
CappyKD said:
Dan,

Did you call them?

If you don't mind my asking, why the need for an external regulator?


Kirk
Click to expand...

I think I spoke to Andrew...but to be fair that was 6-months ago or so. They don't typically do external regulators so mine would get pushed to their custom line.

I need it to be able to power the Mobi-Arc welder...and it requires a non-avalanche style diode rectifier.

I did contact 3 HO alt shops per a recommendation from a MUD vendor. And the one in the midwest, whose name escapes me right now, was about 1-week turn-around and about $200 less (no upcharge for external regulator) for similar performance and quality with an adjustable aluminum cased finned external regulator.
 
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