Jeep cherokee have no power at either field wire at alternator, when alternator fields are connected and key turned on the guage fuse blows... does the pcm control the field circuit? is there a diagram available

generator field current dead, not switching
charge lamp on?
the PCM , does the field current and alternator regulation
so it can be BAD PCM , bad ALT or bad wiring.
id check the fuse link,, for blown, and connections, then test the alternator. PCM last

stock car YJ ? , or all hacked up. (old cars get hacked)
2.5 or 4.0 liter engine? still have a real jeep alternator not upgraded?

loss of electrical power (first rule, we never need to guess.!!!)
not with a voltmeter. (tool that costs $20 )
alternator good (by what means, autozoned?) ( we can find out one car)
but low on gauge. what gauge in dash voltmeter.? sure...
i think you car has no charge lamp only the dash VM.

own an volt meter? a DMM? hand volt meter?

1: if the alternator charge lamp is stuck on driving.
2: is battery voltage at 13.3 to 15vdc with engine at 800 RPM idling
alternator belt not slipping, for sure.....???
if the battery voltage is near 12.5v and falling running that is
an Alternator system failure, note i said, system. !!!

this is first. if we get to here. we can find the real cause.
test 3:
is the charge lamp on keyon, and goes out running?
make sure the big fuse for the alternator in the engine bay fuse
box is not blown, 50amp?

I have no 95 FSM and my online source sucks for 95

Alternator dead: (alt good)
1: belt slipping . engine at 300rpm, nah.
2: fuse blown, the big one. (engine bay fuse box)
3: ;wrong alternator, there are many, most others will fail, even good ones.......
4: alternator ground bad. (end to end, to battery minus)
5: bad wiring to same. bad connections, any to battery or alt.
6: some jeeps the PCM has the field regulator, see link below.
ECU pin 20 , is field pin, it is on 95, 4.0L (engine not stated)

is the CEL lamp on, and throwing code 41 DTC?, alt, field errors?

the alt has 4 pins, battery, field,ground and voltage sense.
The reg is in the PCM. and if bad is a bad $3 transistor..
see same form for fix for that issue..

i think this is same as your. 1996 is big change year.
http://www.jeepforum.com/forum/f12/1993-wrangler-pcm-ecu-ecm-pin-out-diagram-1170004/


you can test the alt, PCM wire pulled !, by full fielding the alt.
grounding the field term, no wires on field pin of alt.
see FSM for details on that.
The PCM modulates the field pin to control charge at all times.

Fault Code 41

Description: Alternator field control circuit open or shorted
Power loss light: Off
Limp-in mode: None

Possible Causes
* Bad connection or wiring - Check the wiring and connections between the logic module and the power module. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.

* Bad voltage regulator circuit - See Diagnosing Your Charging System

Diagnostic Method:
* Trigger Parameters
- Near 0V or near 12V not detected when the field coil driver is turned on or off, respectively

* Results If Component Fails
Fault code 41 is stored. If the condition persists, it will eventually result in a fault code 46 or 47.


Good luck.

Fault Code 41

Description: Alternator field control circuit open or shorted
Power loss light: Off
Limp-in mode: None

Possible Causes
* Bad connection or wiring - Check the wiring and connections between the logic module and the power module. Clean and regrease any corroded connectors with dielectric grease and repair any shorts.

* Bad voltage regulator circuit - See Diagnosing Your Charging System

Diagnostic Method:
* Trigger Parameters
- Near 0V or near 12V not detected when the field coil driver is turned on or off, respectively

* Results If Component Fails
Fault code 41 is stored. If the condition persists, it will eventually result in a fault code 46 or 47.


Nice Jeep, I have the same 5.2L V8; Good luck (remember to rate this answer).

Generator field is not switching properly. In most instances, this codes is related to the alternator, and the alternator will need to be replaced. Check the wire connections to the alternator first, before replacing.

The fuse it doing it's job, you have a short ( Wire that is connected to a ground, that draws too much power )

If you have an electrical schematic ( Repair manual ) find out which wires are connected to that fuse and check them for any chaffing, cuts, unnesassary twists, or corrosion.

If you have a ohm-meter, isolate the system ( by disconnecting the fuse, and other connections. Then check for any resistance on wires that should not be connected ( because you disconnected them ) by having one Lead on the wire's connector and the other meter-lead on your car's frame. A good wire will not have continuity if it is isolated.

Sounds like a short.

The problem sounds intermittent, if you put volt meter on the battery while it is at that 19volt mark/reading(on the gauge cluster) you will be able to see if it is true. If your alternator is really charging over 16volts the lights should be getting brighter then usual and/or they are burning out. Find out ASAP, if the alternator has a defective voltage regulator, it needs to be replaced. Prolong use will damage components.

on the field wires ones a posative and one a negative and the single post gets connected to a wire that runs straight to the main fuse box in the engine compartment then is fused to another wire that goes to the battery have that fuse checked it could be your problem as far as the feild wires the positive side only works when you start the vehicle up to engage the field

Likely you did this already but check fuses in power distribution box near battery (likely two 60a fuses for alt in there). Additionally, was alternator regulator tested or was alt "full fielded" for test. (regulator failure will prevent power made at alt from reaching the battery). Also, check continuity of leads going to alternator to make sure they're OK.