Hi guys, i have a 2001 lb7 truck that has began to flicker and drop to 12 volts on the gauge(at which point the light are dimmd), but it only does it at higher rpm. Alternator, tensioner both replaced 2 yrs ago with GM parts but i know that doesnt mean anything. Im not hearing squeeling or belt slippage. Anybody have any ideas?? Thanks in advance
Voltage Loss
- Thread starter nwodiesel
- Start date
How old are you're batteries? Have they gave weak start since the cold weather moved in?
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Does the voltage ever climb to 14v while the engine is running? What is your voltage before you start the truck - on each of the batteries when disconnected?
If it's only at high rpm's, then the only thing that comes to mind is brushes skipping in the alternator. At low rpm's they stay in contact with the commutator, but at higher rpm's they won't maintain steady contact, and without a field present the alternator won't charge.
Fighting major voltage issues. I lose voltage when running the truck and turning to the tmrighr. When I turn to the left everything is fine. Also when I slow down and engines idkes down the voltage drops to 10vs and everything goes black lights wise. I’ve replaced batteries and alternator. As well as checked all my grounds and positives. Could this be a BCM issue or is it something simple?
I think its a minor issue that you’re over thinking.
Ok, so is the truck easy or hard to start? What is actual voltage at the alternator? Have you load tested the batteries? Ohm the cables???
The reason i ask is that if the truck is slow cranking or hard starting then its battery. If it starts with ease but everything is dimmes or your actual voltage is low then id look at alternator being the issue. You said you changed the alternator thoe? Ive had new go bad out of the box. But, if you are getting more then 12v on a good meter then look at wires. Not so much at the connections but ohm wires. Also sounds like you might have corrosion in the cable.... some simple tests will tell you where the issue is.:thumb:
Fermanator. Not trying to start a pissing match but your thinking of a drill motor not a alternator. An alternator doesnt have brushes or a commutator. I think your talking about windings and armature. You need brushes and a commutator to induce fielding not collect a charge. :hug:
Ok, so is the truck easy or hard to start? What is actual voltage at the alternator? Have you load tested the batteries? Ohm the cables???
The reason i ask is that if the truck is slow cranking or hard starting then its battery. If it starts with ease but everything is dimmes or your actual voltage is low then id look at alternator being the issue. You said you changed the alternator thoe? Ive had new go bad out of the box. But, if you are getting more then 12v on a good meter then look at wires. Not so much at the connections but ohm wires. Also sounds like you might have corrosion in the cable.... some simple tests will tell you where the issue is.:thumb:
Fermanator. Not trying to start a pissing match but your thinking of a drill motor not a alternator. An alternator doesnt have brushes or a commutator. I think your talking about windings and armature. You need brushes and a commutator to induce fielding not collect a charge. :hug:
Well actually he is correct on there being brushes. There are two slip rings (if that is the correct name) similar to a commutator that the brushes run on to get the field current to the windings on the rotor. The possibility of them skipping is low due to them being a continuous ring instead of the multiple contacts of a traditional commutator
You sir’s are correct. I am sorry. I didnt think they had them. Would have thought they were like a stator collecting magnetic fielding and sending it through a voltage regulator....
Huh learned something new today. Now i need to find out why they have brushes? You would have to use a big diode to stop a short so the “generator” doesn’t become a motor. Huh....
Huh learned something new today. Now i need to find out why they have brushes? You would have to use a big diode to stop a short so the “generator” doesn’t become a motor. Huh....
Take a look at this them there picture
The field power is via the regulator. This can act as the "diode you speak of. It will vary the current in the armature to increase or decrease the output of the main windings. There is also a set of diodes on the stator to convert the alternating current to DC and this will also prevent the current flowing backwards.
Being an AC generator or alternator, if current did flow backwards it would try and stall or exibit high resistance to rotation before it burned up. It would not run like a motor.
It is possible to run them as a motor with a three phase drive like used in RC cars, etc by bypassing the regulator and diodes and hooking it straight up to the stator and applying a small current to the armature
The field power is via the regulator. This can act as the "diode you speak of. It will vary the current in the armature to increase or decrease the output of the main windings. There is also a set of diodes on the stator to convert the alternating current to DC and this will also prevent the current flowing backwards.
Being an AC generator or alternator, if current did flow backwards it would try and stall or exibit high resistance to rotation before it burned up. It would not run like a motor.
It is possible to run them as a motor with a three phase drive like used in RC cars, etc by bypassing the regulator and diodes and hooking it straight up to the stator and applying a small current to the armature
Ouch. Well sir, with out the rectifier you have the making of a squirrel cage motor....
There is very little difference between an ac electric motor and an ac power generating alternator. They both have magnetic fields and coils of wire that react to it. It can act as a motor. Also the voltage regulator varies the output not the diode I speak of. The rectifier (diodes) inverts the ac to dc. Only flows one way. The increase and decrease of output is controlled be the field. The greator the field the more current it will produce. Greater the load demand then more field is applied to meet demands. Sorry eyes dont have a cute pitcher 4 you to to see what eyes sane...:roflmao: no hard feeling brother i tryed to apologize.
There is very little difference between an ac electric motor and an ac power generating alternator. They both have magnetic fields and coils of wire that react to it. It can act as a motor. Also the voltage regulator varies the output not the diode I speak of. The rectifier (diodes) inverts the ac to dc. Only flows one way. The increase and decrease of output is controlled be the field. The greator the field the more current it will produce. Greater the load demand then more field is applied to meet demands. Sorry eyes dont have a cute pitcher 4 you to to see what eyes sane...:roflmao: no hard feeling brother i tryed to apologize.
If it is cranking fine and your voltage is erratic, check the positive wire from the driver battery to the UBEC. I had a similar issue and the wire ended up being faulty: Voltage was always a bit low from the cluster gauge, then one day all my interior lost power. Well, I went to test the wire and ended up burning my hand - Truck was only running for 10-15 seconds before it happened too. I replaced it with 4 gauge wiring and the old one was completely corroded.
I know they have brushes, changed more than a few sets. And I've had a couple where they would charge fine at idle, increase RPM's and they would stop charging. Put in brushes and all was good. It doesn't happen often, but I've seen it.