Alternator Voltage low
Fleet Owner
Joined: Nov 2003
Posts: 27,897
Likes: 3,615
Here is the alternator output curve based on rpm:
https://www.fleet.ford.com/truckbbas...trkelec_06.pdf
(on page 5)
65-80 amps (temperature dependent) at 750 rpm and about 70-85 amps at 900 rpm.
https://www.fleet.ford.com/truckbbas...trkelec_06.pdf
(on page 5)
65-80 amps (temperature dependent) at 750 rpm and about 70-85 amps at 900 rpm.
Postmaster
Joined: Jan 2005
Posts: 4,424
Likes: 12
From: BC Canada
High idle mod would be the trick, running at 1250 rpm, pully on the alt 2 times that. You will get 100 amps on the stock, maybe 130 on the new 185. Another trick you can do is run a dedicated 8 gauge wire to run that fridge through a switch. So when you are running the truck, the fridge can be running off the batteries and alt of the truck directly.
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Junior User
Joined: Aug 2010
Posts: 80
Likes: 0
From: Germany NRW
Thank you for the great support! 
After engine start and after the 2min for the glow plugs, I had the voltage at 13,6V the engine rpm is in this case between 1600 and 1800.
The battery isn't full, because the voltage at the battery is 12,0-12,2V when I turn off the engine and wait a few minutes.
Where do I check the FICM voltage?
In Germany we had to change the trailer wires to a 13pole connector with a special cable. The core size is 2,5mm² (sorry, I don't know the american spec for this size). It could be a little bit bigger core size, but it works.
Now I'm not sure, what to do. But I think the 185A alt from dc power you recommended should be the solution!
Because you had to log in to the Dodge-Forum.eu
to show, the pics, of my truck, I do the pics in this post!
After engine start and after the 2min for the glow plugs, I had the voltage at 13,6V the engine rpm is in this case between 1600 and 1800.
The battery isn't full, because the voltage at the battery is 12,0-12,2V when I turn off the engine and wait a few minutes.
Where do I check the FICM voltage?
In Germany we had to change the trailer wires to a 13pole connector with a special cable. The core size is 2,5mm² (sorry, I don't know the american spec for this size). It could be a little bit bigger core size, but it works.
Now I'm not sure, what to do. But I think the 185A alt from dc power you recommended should be the solution!
Because you had to log in to the Dodge-Forum.eu
to show, the pics, of my truck, I do the pics in this post!
Hotshot
Joined: Aug 2006
Posts: 17,398
Likes: 317
From: Whittier, CA
Looks like a bad battery to me. Have them load tested.
Hotshot
Joined: Aug 2006
Posts: 17,398
Likes: 317
From: Whittier, CA
Load test them anyway.
I'm not sure what else to say, except that 13.6V is plenty to charge higher than 12.2. Unless something is loading them down when you are taking the reading.
Cable connections are something else to check.
I'm not sure what else to say, except that 13.6V is plenty to charge higher than 12.2. Unless something is loading them down when you are taking the reading.
Cable connections are something else to check.
Hotshot
Joined: Aug 2006
Posts: 17,398
Likes: 317
From: Whittier, CA
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Junior User
Joined: Aug 2010
Posts: 80
Likes: 0
From: Germany NRW
Sorry, in english it's a relay.
An electically operated switch, in my case it's activated at 13,7V!
O.K., I think, when I would drive more than an hour, I can messure a higher batterie voltage, but most times I drive max. half an hour!
An electically operated switch, in my case it's activated at 13,7V!
O.K., I think, when I would drive more than an hour, I can messure a higher batterie voltage, but most times I drive max. half an hour!
Hotshot
Joined: Aug 2006
Posts: 17,398
Likes: 317
From: Whittier, CA
Okay, so you want the relay to engage to turn on what? And you want it to turn on at 13.7V?
I can tell you that that would not work on my truck. I only get more than 13.7 when my truck is at higher RPM. I think my alternator is on the low side of design spec, but it has always been that way and I don't consider it below normal. I'm not sure you can bet on any alternator putting out 14V at idle, or even high idle. Some will, some won't.
For what it's worth, my RV charger doesn't put out more than 13.6 in charge mode, and only 13.2 in float mode. It has a boost mode of 14.4, but only does that when the batteries are very low.
I think you need a relay with a lower threshold voltage.
Still don't know what to say about batteries that are only 12.2V. I assume you are taking that reading with all loads removed.
I can tell you that that would not work on my truck. I only get more than 13.7 when my truck is at higher RPM. I think my alternator is on the low side of design spec, but it has always been that way and I don't consider it below normal. I'm not sure you can bet on any alternator putting out 14V at idle, or even high idle. Some will, some won't.
For what it's worth, my RV charger doesn't put out more than 13.6 in charge mode, and only 13.2 in float mode. It has a boost mode of 14.4, but only does that when the batteries are very low.
I think you need a relay with a lower threshold voltage.
Still don't know what to say about batteries that are only 12.2V. I assume you are taking that reading with all loads removed.
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Junior User
Joined: Aug 2010
Posts: 80
Likes: 0
From: Germany NRW
The relay is a a standard D+ Detector.
The F350 ist the first truck, where I had this problems. O.K. European cars reach the 13,8V every time, the engine run. The Dodge Ram V10 I had before also. This is the first vehicle, I see, that does not reach the 13,8V. So the relay doesn't work correctly.
The reason for this relay is, that I don't want to much load (especialy in cold conditions) when I'm starting the truck.
My camper has 3 very big batteries inside and a voltage lifter, which transform a low voltage at the trailer plug into 14V wit 8A.
If the engine is off, the D+ Detector switch the DC off, which is routed to this connector. So I'd no extra load on the truck batteries.
The F350 ist the first truck, where I had this problems. O.K. European cars reach the 13,8V every time, the engine run. The Dodge Ram V10 I had before also. This is the first vehicle, I see, that does not reach the 13,8V. So the relay doesn't work correctly.
The reason for this relay is, that I don't want to much load (especialy in cold conditions) when I'm starting the truck.
My camper has 3 very big batteries inside and a voltage lifter, which transform a low voltage at the trailer plug into 14V wit 8A.
If the engine is off, the D+ Detector switch the DC off, which is routed to this connector. So I'd no extra load on the truck batteries.
Hotshot
Joined: Aug 2006
Posts: 17,398
Likes: 317
From: Whittier, CA
I just went out for an errand, and watched my voltage. When I started the truck, once the glow plugs went out, my voltage bounced between about 14v max and 13.7 min. My drive was about 2 miles, and these were the values the entire time.
Coming back, my voltages were between 13.5 and 13.7. I don't think this has anything to do with outside temp. It is because my truck was cold, having not yet been driven today, and the batteries were slightly depleted from the glow plugs and starting. As you can see, my voltages are within 1/10th volt of yours when warmed up.
As you can also see, on my return trip, you relay would not have remained closed.
I don't think any alternator should run at a constant 14.4 volts. That will boil your batteries on any lengthy trip.
For what it is worth, my voltages are read from my Edge Insight, which displays the voltage hitting the PCM, not directly from the batteries.
Coming back, my voltages were between 13.5 and 13.7. I don't think this has anything to do with outside temp. It is because my truck was cold, having not yet been driven today, and the batteries were slightly depleted from the glow plugs and starting. As you can see, my voltages are within 1/10th volt of yours when warmed up.
As you can also see, on my return trip, you relay would not have remained closed.
I don't think any alternator should run at a constant 14.4 volts. That will boil your batteries on any lengthy trip.
For what it is worth, my voltages are read from my Edge Insight, which displays the voltage hitting the PCM, not directly from the batteries.
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Junior User
Joined: Aug 2010
Posts: 80
Likes: 0
From: Germany NRW
Thank you for your tour with a look on the voltage!
Your voltage ist much better than what I get from the alternator.
If th D+ Detector bcomes 13.7V for a second, the unit will switch.
The level, the unit sitch off is 13,4V.
I think, I will try the bigger alternator. In a 2 weeks, I'll drive 2000mls. and will have a eye at the voltage. after this trip, I will order the new alternator and I'll see if this is the solution.
Your voltage ist much better than what I get from the alternator.
If th D+ Detector bcomes 13.7V for a second, the unit will switch.
The level, the unit sitch off is 13,4V.
I think, I will try the bigger alternator. In a 2 weeks, I'll drive 2000mls. and will have a eye at the voltage. after this trip, I will order the new alternator and I'll see if this is the solution.
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