Alternator hot?
Thread Starter
|
Logistics Pro
Joined: Mar 2002
Posts: 3,881
Likes: 84
From: Wake Forest, NC
Alternator hot?
I think my GPR died tonight causing my glowplugs to get stuck on and drain the batts. While tracking down the wiring, the top lug of the GPR broke off. So after I rigged up a heavy duty solenoid (i had to change it over from internally grounded), I noticed that my alternator still got hot. I had assumed it was that way because of the GPR being stuck. I used a cheesy amp meter and appeared to bet getting 75 amps draw off the back of the alternator, but the field current could have been interfering with the reading. At the GPR and AIH relay there wasn't any draw, or voltage on the outbound side. Somewhere between the relays and the alt it's taking a lot of power. Even without the cheesy amp meter I can tell because the lead is pretty warm. At the battery connection on the passenger side where the alt wire connects there was only about 20 amps of draw. I'm going to run another alt lead to the driver side battery but figured I'd point it out. I was going to run a cable to the power lug behind the air box because it would be a discrete install, but it's pretty crusty so I figure I'll leave it alone... maybe.
Let you all know if it improves the draw on the alternator.
Let you all know if it improves the draw on the alternator.
Fleet Mechanic
Joined: Jan 2007
Posts: 1,741
Likes: 3
While you may, in fact, have a problem somewhere, keep in mind that modern vehicles will pull 50-75 amps of running load on just the motor -- meaning no lights, no radio, no accessories; just keeping the motor running.
The fuel pump, the injectors, the ECM, the sensors, etc... Last I knew, the injectors took between 5-10 amps EACH, each sensor required 2-5 amps, etc...
-blaine
The fuel pump, the injectors, the ECM, the sensors, etc... Last I knew, the injectors took between 5-10 amps EACH, each sensor required 2-5 amps, etc...
-blaine
Thread Starter
|
Logistics Pro
Joined: Mar 2002
Posts: 3,881
Likes: 84
From: Wake Forest, NC
Yep they sure do. Esp a powerstroke. Alot of alts now are topping 160 to 180 amps from the factory.
Not to mention charging up two big batteries after they've been running glow plugs and cranking over a cold (but not as big as yours apparently) diesel.
Not to mention charging up two big batteries after they've been running glow plugs and cranking over a cold (but not as big as yours apparently) diesel.
Lead Driver
Joined: May 2003
Posts: 9,303
Likes: 48
From: Lyndonville, Vermont
The batteries will take a heavy draw if they are down. As far as how much for a running engine takes its not much for a gas motor under 30 amps and maybe under 20 for some engines. Mine runs about 25 amps after the battery gets topped off...Diesel might be less since no ignition but maybe not cause of the bigger fuel pump.
Dick
Dick
Fleet Mechanic
Joined: Jan 2007
Posts: 1,741
Likes: 3
You're forgetting how much current the fuel injectors draw.
SOME gasoline fuel injectors can draw as many as 10-12 amps at full-blast (i.e. high RPM); multiply that by 8 injectors, and suddenly you start talking a lot of current. (8x12=96A) The ignition doesn't pull but 3-5 amps, since it's all about voltage (not amps) in the ignition.
Modern (OBD-II) engines have over a dozen sensors, and generally, these sensors are driven such that the ECM monitors how much current it takes to generate/hold a certain voltage. That means 20-30 amps for all the sensors.
Pretty soon, once you start adding in all the interior goodies, you can see why a 200A alternator (or dual 140's, in the SD's case) are all but REQUIRED.
My '79 Chebby had a 70A alternator. Worked great. My '89 Chebby had a 105A alternator; virtually identical engine, 'cept TBI fuel injection. Engine needed over twice the current. 105A was just BARELY enough to keep the lights from dimming. Especially when using the power windows.
I'd be surprised if my '07 PSD drew any LESS than 100A just sitting there idling warm. 160-ish if the glow plugs are cycling.
-blaine
SOME gasoline fuel injectors can draw as many as 10-12 amps at full-blast (i.e. high RPM); multiply that by 8 injectors, and suddenly you start talking a lot of current. (8x12=96A) The ignition doesn't pull but 3-5 amps, since it's all about voltage (not amps) in the ignition.
Modern (OBD-II) engines have over a dozen sensors, and generally, these sensors are driven such that the ECM monitors how much current it takes to generate/hold a certain voltage. That means 20-30 amps for all the sensors.
Pretty soon, once you start adding in all the interior goodies, you can see why a 200A alternator (or dual 140's, in the SD's case) are all but REQUIRED.
My '79 Chebby had a 70A alternator. Worked great. My '89 Chebby had a 105A alternator; virtually identical engine, 'cept TBI fuel injection. Engine needed over twice the current. 105A was just BARELY enough to keep the lights from dimming. Especially when using the power windows.
I'd be surprised if my '07 PSD drew any LESS than 100A just sitting there idling warm. 160-ish if the glow plugs are cycling.
-blaine
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
Likes: 1,678
From: Stephensville WI
Aside from all that, alternators do normally get pretty hot. It is normal for them to be hot enough that you can't hold your hand on them.
You may want to have your batteries "load-tested". Also, it'd be a good idea to throw a charger on them, let the batteries charge overnight. Cold weather and batteries that are weak or run down can mean your PSD won't be going anywhere.
You may want to have your batteries "load-tested". Also, it'd be a good idea to throw a charger on them, let the batteries charge overnight. Cold weather and batteries that are weak or run down can mean your PSD won't be going anywhere.
Thread Starter
|
Logistics Pro
Joined: Mar 2002
Posts: 3,881
Likes: 84
From: Wake Forest, NC
What I found interesting about the hot alternator, is the feed cable was warm close to the alt, but at the GPR and AIH relay, and at the battery connection it was normal. I've gotten burned on alternators before so they definitely can get hot.
Whatever took out the system drained it pretty good. I've had the batteries charging many hours. One almost all day today, it was a little weaker than the other. I had both charging together for 6 hours last night and probably all night tonight. They are almost there though.
I have a feeling that nothing was drawing down the alternator. I think the hot cable is coming from the alternator itself being warm and just conduction. Checking the voltage again I found it to be on the low side. Around 13.4 volts yesterday, 12.5 today. So almost no charge. The slip rings and one brush was about worn out.
Whatever took out the system drained it pretty good. I've had the batteries charging many hours. One almost all day today, it was a little weaker than the other. I had both charging together for 6 hours last night and probably all night tonight. They are almost there though.
I have a feeling that nothing was drawing down the alternator. I think the hot cable is coming from the alternator itself being warm and just conduction. Checking the voltage again I found it to be on the low side. Around 13.4 volts yesterday, 12.5 today. So almost no charge. The slip rings and one brush was about worn out.
Trending Topics
Cargo Master
Joined: Apr 2007
Posts: 2,659
Likes: 2
A cable will always be hottest near the terminal end because of th higher resistance at the connection.
The alternator isn't going to overheat unless it is clogged with debris. It is designed to run continuous at full output. You can't work it too hard.
The alternator isn't going to overheat unless it is clogged with debris. It is designed to run continuous at full output. You can't work it too hard.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Thread Starter
|
Logistics Pro
Joined: Mar 2002
Posts: 3,881
Likes: 84
From: Wake Forest, NC
Looks like the alternator was fighting itself internally. Nothing else was drawing down the system, a new alternator and some time on the battery charger to restore the batteries fixed it up!
Thread
Thread Starter
Forum
Replies
Last Post
RogerP
1999 - 2003 7.3L Power Stroke Diesel
23
Feb 26, 2014 05:30 AM
jakescars
1999 - 2003 7.3L Power Stroke Diesel
18
Nov 6, 2009 09:59 AM
bdrummonds
1999 - 2003 7.3L Power Stroke Diesel
20
Dec 20, 2008 01:41 PM
sdetweil
1948 - 1956 F1, F100 & Larger F-Series Trucks
6
Jun 13, 2008 09:10 PM