Another alternator question

[Groelzj]

Good morning all. Working on SWMBO's truck today. We have a 2004 Ranger 4.0. The alternator went out a couple months ago and I replaced the brushes and voltage regulator. Just the other day, it wouldn't start. Figured we left the door ajar or something and jumped it. It's done the same now a couple times. She said yesterday while driving, the ABS light turned on and the radio turned off. I checked the battery voltage when she got home - 12.85. This morning it was 9.95v. I'll take the battery to be tested at lunch time to see if a bad battery could be compounding the problem.

I took the truck to work this morning with my OBDII bluetooth reader plugged in, and Torque monitoring the voltage on my android phone. The alternator intermittently cuts out, but when I step firmly on the brakes, it comes back on.

Seems to behave like a loose connection...the momentum of the wires causing the connection to drop, but I can't find a wire that makes/breaks connection when I move it.

Any advice? The small wires at the alternator don't misbehave when wiggled/pulled and when the alternator goes out while driving, by the time I get to a stop, I've got charge again.

Thanks in advance!
Jon

 

[RonD]

2004 probably has "smart charging", computer controlled alternator output.

Just to clarify, the voltage in the system should never drop below battery voltage, if battery is 12.3v then when watching volts on monitor it should not drop lower than that when engine is running, so what do you mean alternator cuts out?

"normal" operation would have system voltage at 14.5v just after starting, then it will slowly go down to 13.5v after battery is recharged.
As you turn on head lights or blower fan the voltage should drop then come back up to 13.5v.
That's the voltage regulator working as it should.

The "smart charger" can change all this and not sure how to test that
This is a wiring diagram for the 2004 charging system: http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8036dee8

If you think it is a loose wire then I would check the engine ground first, but I would think starter motor would be effected by that as well.