Christopher James
New Member
- Joined
- July 17, 2018
- Messages
- 1
- Reaction score
- 0
- City, State
- Manchester, WA
- Year, Model & Trim Level
- 2005 Explorer Eddie Bauer
The problem:
At operating temp. exciter wire will not start charging alternator when starting vehicle
The facts:
Alternator works fine at cold start.
When ALT is functioning it puts out a normal 14.3 volts, Battery and ALT are new.
This is actually the second new ALT as I was having this problem and assumed bad new ALT
Only malfunctions when vehicle is at warm start
Can manually force charging by revving engine, but not always works
When the exciter wire is plugged in and working fine the volts are 7.8
When the exciter wire is not functioning the volts drop to 1.2
When the exciter wire is unplugged from ALT while engine running the volts in wire are over 12
The second its plugged back in the jolt of being reconnected will start ALT charging and wire volts
drop back down to 7.8
Can manually start ALT charging by bridging a test light from POS Battery Terminal to exciter wire.
Volt drop test from POS battery term. to ALT Positive term. shows normal
Volt drop test from Neg battery term. to ALT body shows normal.
Unknown:
What is the "normal" volts for exciter wire when plugged into ALT, engine on?
Is it normal for exciter wire volts to drop from over 12 to 7.8 volt while under load from ALT?
Why does it only malfunction when vehicle is at operating temp?
Is the problem
A) in the ALT creating excessive volt draw when hot and not triggering charging?
B) Wiring or PCM problem (again exciter wire volts only drop when wire plugged into ALT)
What to do:
Give up doing this myself and pay dealership to find the problem?
Pay $25 + shipping for a salvage OEM Alternator, which would at least tell me if its the ALT or the vehicle wiring/PCM and still possibly have to pay the dealership?
At operating temp. exciter wire will not start charging alternator when starting vehicle
The facts:
Alternator works fine at cold start.
When ALT is functioning it puts out a normal 14.3 volts, Battery and ALT are new.
This is actually the second new ALT as I was having this problem and assumed bad new ALT
Only malfunctions when vehicle is at warm start
Can manually force charging by revving engine, but not always works
When the exciter wire is plugged in and working fine the volts are 7.8
When the exciter wire is not functioning the volts drop to 1.2
When the exciter wire is unplugged from ALT while engine running the volts in wire are over 12
The second its plugged back in the jolt of being reconnected will start ALT charging and wire volts
drop back down to 7.8
Can manually start ALT charging by bridging a test light from POS Battery Terminal to exciter wire.
Volt drop test from POS battery term. to ALT Positive term. shows normal
Volt drop test from Neg battery term. to ALT body shows normal.
Unknown:
What is the "normal" volts for exciter wire when plugged into ALT, engine on?
Is it normal for exciter wire volts to drop from over 12 to 7.8 volt while under load from ALT?
Why does it only malfunction when vehicle is at operating temp?
Is the problem
A) in the ALT creating excessive volt draw when hot and not triggering charging?
B) Wiring or PCM problem (again exciter wire volts only drop when wire plugged into ALT)
What to do:
Give up doing this myself and pay dealership to find the problem?
Pay $25 + shipping for a salvage OEM Alternator, which would at least tell me if its the ALT or the vehicle wiring/PCM and still possibly have to pay the dealership?
