2005 Ford Ranger Alternator?? Problem

[Rand]

Vehicle:
2005 Ford ranger 4x4 XLT 5MT 4.0SOHC engine.

Problem: Battery dead, intermittent low idle, battery not charging.

Tried so far:-- My Father replaced the ~~8yr old motorcraft battery before he called me. Still does it.

I went over with a meter and tried Diagnosing it but it seems the problem is intermittent.

Basically When he first got home from eating dinner(truck was warm) I was reading 12.85V at battery terminals and also across the wiring. Started truck. Voltage was 13.6V at the battery. Rev'ed truck to 1500rpm Voltage dropped to 12.5V and lights got dim. Also idle was 600rpm (usually idle at 750)

I determined the alternator was doing pretty much nothing at the time.

Repeated starting truck and testing voltage. (about 4x)

The voltage continued dropping to about 12.2V never above 12.45V

We started checking the wiring on the alternator it seems in good condition.

I put battery on charge for 20min(it was getting low)

Came back out. Started truck.. alternator was working again. HEadlights bright.. reading 14.2V at the alternator (red cable to ground) NEver idled bad again. Works fine?

What is this problem a bad voltage regulator in the alternator?

I put the truck on overnight 2amp charge(its a smart charger will auto switch to float)

Looking to buy parts and fix this tomorrow.


What I am thinking:

1. Something bad in alternator
or

2. Bad/loose wiring.



Any ideas advice/opinions from people who work on these for a living?

Could this be a failing alternator when its warm?

this is what I think would be the best symptom of the problem but I'm not sure what it means

"Basically When he first got home from eating dinner(truck was warm) I was reading 12.85V at battery terminals and also across the wiring. Started truck. Voltage was 13.6V at the battery. Rev'ed truck to 1500rpm Voltage dropped to 12.5V and lights got dim"


Oh and the truck is pretty much 100% stock.. it has skid plates etc.. but no aftermarket electrical anything etc

 

[stranger706]

Our previous 2005 Explorer did the same thing around 85,000 miles. I replaced a good battery chasing the symptoms. Shotgun maintenance is expensive. Ended up being the alternator. Not sure what exact part, I just know that a new one fixed the problem. Has to be oem or the pcm won't like it.

 

[Chris142]

Worn alternator brushes?

 

[NHGUY]

Originally Posted By: Chris142
Worn alternator brushes?

Thats what I was thinking.When worn,they have a tendency to operate at an angle,making very little commutator contact.

 

[Donald]

Originally Posted By: NHGUY
Originally Posted By: Chris142
Worn alternator brushes?

Thats what I was thinking.When worn,they have a tendency to operate at an angle,making very little commutator contact.


Maybe, but remember the brushes just pass the excite current, not the total 60 AMP output of the alternator. Still they do need to work properly. On my Volvo, they could be replaced without even removing the alternator.

 

[Rand]

Sounds reasonable. I think most likely I'll go hit o'rielly tomorrow and snag one..
I get corp discount there so its quite a bit cheaper than AZ or AAP. Dont really want to wait till next week for rock auto.

 

[Donald]

Originally Posted By: Rand
Sounds reasonable. I think most likely I'll go hit o'rielly tomorrow and snag one..
I get corp discount there so its quite a bit cheaper than AZ or AAP. Dont really want to wait till next week for rock auto.


For alternators & starters I like to "shop local" and try and go to a local rebuilder if there is one around. They need your business and are super knowledgeable in most cases. You will not walk away with a piece of cheap overseas junk from a local rebuilder.

 

[Rand]

I considered that but would they have one I could pickup at 4pm and put on the truck? I dont have a day off work till next wends. Also I would be driving 30 miles to my dad's work to put it on for him. I dont have time to drop anything off for a day and go pick it up.

 

[Rand]

Thanks for the help guys. After having some daylight it was apparent the brushes were toast in the alternator.

Ford in their genius ways in 2005 switched to a different alternator that has a replaceable assembly but they dont sell the kit to replace them....

130AMP "lifetime" cheapo purchased from AZ and installed. Voltage was reading high but didnt have a known good meter to check it with.

Btw the ford price was 624$ for new motorcraft with 12m/12k warranty or 537$ for reman with samee warranty.. they can shove that. The duralast? one was 137$ and Its a 30min job max with 2 people to change it if this thing dies.

I'll be following up on monday with the right tools


Thanks again.