Low Voltage, 03 4.0
#1
Low Voltage, 03 4.0
This is on Kevoo's truck, not mine.
It's a 2003 4.0 auto, essentially no electrical mods.
Everything was fine, and randomly while driving it almost stalled and showed a low voltage condition.
We had the alt checked, it's within limits
The battery should be fine, it cranks up with full power
I used a jumper from the alt to battery...and it made it hard to start and run a little rough at idle, so I'm not sure what that meants...
We cleaned the battery terminals...that did no difference
When you rev the truck up, it will go up to regular voltage, when it is idleing with the lights on and ac, it is all the way down (running off the battery) and everything dims...engine runs a little rough.
Any ideas???
I am almost thinking it's the battery...event though it starts fine, maybe something is still wrong with it?
It's a 2003 4.0 auto, essentially no electrical mods.
Everything was fine, and randomly while driving it almost stalled and showed a low voltage condition.
We had the alt checked, it's within limits
The battery should be fine, it cranks up with full power
I used a jumper from the alt to battery...and it made it hard to start and run a little rough at idle, so I'm not sure what that meants...
We cleaned the battery terminals...that did no difference
When you rev the truck up, it will go up to regular voltage, when it is idleing with the lights on and ac, it is all the way down (running off the battery) and everything dims...engine runs a little rough.
Any ideas???
I am almost thinking it's the battery...event though it starts fine, maybe something is still wrong with it?
#6
Throw a volt meter on the battery and watch it. I think the magic number it shouldn't fall under is 13.8v with the engine running and alternator running properly.
#7
#8
I'm with ccernst, put a meter on the battery. If it holds voltage with the truck idleing, the alternator is working like it should. If the voltage drops with A/C and lights on, then more than likely the regulator is bad. You should get a momentary drop in voltage across the meter, but the regulator should adjust the voltage output up to compensate. If voltage does not come back up, then the regulator is bad.
This is also making the assumption that both the original and replacement alternator are functioning properly.
This is also making the assumption that both the original and replacement alternator are functioning properly.
#10
#11
#12
Yes, the voltage regulator is a solid state unit built into the alternator. It has to be bad. Did he get a remanufactured or rebuilt one?
#13
#14
#15
Haven't got a DMM on it yet, looks to be less than 12v because it is running off the battery.
At about 2k rpms it jumps up to normal 13.5-14.4 volts, it is in the normal range.
The whole thing I am saying is that the new alt didn't do anything...ran the exact same.
With a jumper from alt to battery the truck wanted to die...
I am going to try to run it without the battery hooked up and see what the volts are...seems like the battery may be drawing too much voltage
At about 2k rpms it jumps up to normal 13.5-14.4 volts, it is in the normal range.
The whole thing I am saying is that the new alt didn't do anything...ran the exact same.
With a jumper from alt to battery the truck wanted to die...
I am going to try to run it without the battery hooked up and see what the volts are...seems like the battery may be drawing too much voltage
#16
it may not run without the battery but you may have just said the problem, theres a wire that is hot to energize the alternator, not remembering what it is called right now so sorry for the shady discription
long story short, if this wire is not hot, when the alternator spins faster than 2k rpm it will energize itself...ill get back to you on this when it isnt bedtime
long story short, if this wire is not hot, when the alternator spins faster than 2k rpm it will energize itself...ill get back to you on this when it isnt bedtime
#17
Disconnecting the battery can fry the voltage regulator. The battery balances the output of the alt.
Sounds to me its a wiring issue. You need power in to the alt to get power out. Check the connectors on the alt for damage or corrosion. Also look at the ground on the battery and from the engine to chassis. (usually at the wiper motor)
Is the battery light on?
Sounds to me its a wiring issue. You need power in to the alt to get power out. Check the connectors on the alt for damage or corrosion. Also look at the ground on the battery and from the engine to chassis. (usually at the wiper motor)
Is the battery light on?
#18
#19
I don't know if it helps, but I just replaced my starter cause it was drawing every amp my battery could put out...resulted in a junked battery.
Didn't realize until I turned on my hella 500 lights and my truck would stall on the highway cause I was borderline "not enough juice". 10v isn't enough to run a truck. Found out first hand.
Didn't realize until I turned on my hella 500 lights and my truck would stall on the highway cause I was borderline "not enough juice". 10v isn't enough to run a truck. Found out first hand.
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