replaced alternator still have charging issues??

[basilry]

Was getting a check gages light and the alternator was running at about 8 volts. The gague seemed to be jumping around for a month or so now. So last night I replaced it with a new Bosch. Everything was working ran to get fuel and it was charging like it should. This morning jumped in the truck on my way to the shop and my check gages light came on and the gague is at 8 volts again? Rechecked the connections and everything is good and tight. What else am I missing?? Broken wire?

 

[PWong]

Alternator was NOT your issue.
Load test both batteries to make sure they are good.
Make sure ALL ELECTRICAL CONNECTIONS on the charging/batteries system are good, including GROUNDs.
With engine idling and have some electrical loads on, measure the voltage between the center of the positive and negative post of each battery.
They should have the SAME readings, otherwise the crossover cable was bad.

ALL electrical loads were connected to the driver side battery except the grid heater which was connected to the passenger side battery.
A GOOD ELECTRICAL CONNECTION between the two battery positive posts is vital.
Otherwise the driver side battery would be undercharged and passenger side battery would be overcharged.

The gauge reading inside the cab reflects the driver side battery voltage only. The passenger side battery voltage was never being monitored.

 

[Karter]

I had basically the same symptoms. I replaced the alternator, thinking it was failing. Nope, same issue. Turns out the grid heater relay was stuck and causing the grid heater to draw a ton of power all the time. I took the green wire, that feeds the grid heater relay, off the battery (pass side) and everything is back to normal. According to other TD'ers, the relays fail from time to time. I have ordered a new relay from Geno's to fix mine.

 

[Bob4x4]

Voltage drop testing is a very underused tool every DIY guy or pro should be using

 

[basilry]

Today I had some free time between errands with the family and was wiggling wires and cleaning terminals and following wires to look for damage. I had the truck running for about 2 minutes or so and noticed a burning smell. Tracked that back to the alternator. Hotter than F!!!. Everything else was cool. So I'm assuming something is wrong with my new alternator?? Will be pulling it off tomorrow to have it tested.

 

[p-Bar]

Today I had some free time between errands with the family and was wiggling wires and cleaning terminals and following wires to look for damage. I had the truck running for about 2 minutes or so and noticed a burning smell. Tracked that back to the alternator. Hotter than F!!!. Everything else was cool. So I'm assuming something is wrong with my new alternator?? Will be pulling it off tomorrow to have it tested.

Have em test the new one before you walk out the door

 

[MichaelOverfield]

Some good advice on this thread. You say alternator was a new Bosch, that is the choice to go with. Having worked in a parts store for a time, I never get the re-man units, no matter what the warranty coverage.. because I got to see how often the fail.. not worth the labor time to repeat the install. Most Remans only replace the minimum items.. almost never the stator or rotor windings, and they can have insulation breakdown overtime and fail also. Also not a bad plan to have a pre-test on the new unit.

That said, I'd vote also that it sounds like a stuck relay on the grid heaters from what you described.

 

[Ozymandias]

An Alternator that is working hard producing Power will get hot very fast more then to touch.
That isn't a sign to tell it is faulty.

But checking the car with a decent scanner would be the way to go. The Alternator is controlled by the ECM.

 

[p-Bar]

I agree with Ozy in regards to the heat .

 

[basilry]

Just took off the wire for the grid heater and no change. Had both my old and new alternator tested and they are both good. Now were thinking it must be in the ecm?? I have to crawl up in the rafters to find my old one that was replaced due to the windshield wipers not working years ago and plug that one back in to see what happens. I have 4 codes that cameup...p2509 power down data lost....pp2509charging system output low...pp2509 charging system error...p0514 battery temperature sensor rationality.....

 

[p-Bar]

Just took off the wire for the grid heater and no change. Had both my old and new alternator tested and they are both good. Now were thinking it must be in the ecm?? I have to crawl up in the rafters to find my old one that was replaced due to the windshield wipers not working years ago and plug that one back in to see what happens. I have 4 codes that cameup...p2509 power down data lost....pp2509charging system output low...pp2509 charging system error...p0514 battery temperature sensor rationality.....

Can you try resetting codes? Clean battery cables . Check and clean negatives going to fender this is a common problem. How old are your batteries? Another common problem.

 

[basilry]

The codes have been cleared and all the connections cleaned. I left the grid heater cable off and will see what happens in the morning. Batteries are 2 or 3 years old and load tested good.

 

[basilry]

Truck must have been running off of the batteries alone...went out this morning to fire it up and it turned over once and click click click.

 

[PWong]

Truck must have been running off of the batteries alone...went out this morning to fire it up and it turned over once and click click click.

Get the truck started up running.
Turn on all the electrical loads then measure the driver side battery voltage and passenger side battery voltage and post please.

 

[PWong]

A BAD electrical connection with resistance would work as a heater when high current flows through for a period of time.

 

[Ozymandias]

I had once a Problem with my ignition switch, I didn't shut down completely, electronics stayed On, that drained the batteries down over night.
Also the alternator had a hard job to reload the batteries then.

there was a thread about this.

 

[p-Bar]

Get the truck started up running.
Turn on all the electrical loads then measure the driver side battery voltage and passenger side battery voltage and post please.

Can't do that the batteries are in parallel . I would charge both of them and have them load tested

 

[PWong]

Can't do that the batteries are in parallel .

Why NOT???
What prevent not doing that???
When there was a BAD/RESISTANCE electrical connection between the two battery positive posts the two batteries were NOT IN PARALLEL anymore.
There was a series resistance between them and hence voltage drop between them.

 

[p-Bar]

The batteries are feeding one another. You would have to pull a cable off of one to measure.

 

[PWong]

The batteries are feeding one another. You would have to pull a cable off of one to measure.

There were NOT feeding one another when there was a resistance between their positive posts.
The load was on the driver side battery.
The alternator charging current flowed to passenger side battery first then through the resistance then to driver side battery.
Passenger side battery would see FULL alternator output voltage and overcharged.
Driver side battery would see partial alternator output voltage and undercharged.
ECM monitors driver side battery voltage to determine field current to alternator and hence low voltage check gauge light come on and at the same time passenger side battery smoked.