1992 charging problems

Jordan92stang

New Member
Aug 22, 2018
3
0
1
44
North Augusta
Hi I have a 92 mustang LX 5.0 I have a new battery a new alternator (swapped to the 3g alternator) new ground strap and ground wire for the battery new gauges and it only charges to 11 volts has anyone had this problem and know a fix for it and I have went through 4 alternators still same problem (130 amp alternator and 200amp )
 
  • Sponsors(?)


Boostedpimp

15 Year Member
May 8, 2003
1,020
340
114
NJ
The g3 alternators come with a larger pulley on them then the stock fox pulley. That means the pulley turns slower and less at idle which means less charging at idle. I would measure the pulley and see what you have or swap your factory pulley on the 3g alternator if you still have it and measure your volts
 

Jordan92stang

New Member
Aug 22, 2018
3
0
1
44
North Augusta
The g3 alternators come with a larger pulley on them then the stock fox pulley. That means the pulley turns slower and less at idle which means less charging at idle. I would measure the pulley and see what you have or swap your factory pulley on the 3g alternator if you still have it and measure your volts
I ordered 2 from lmr and I didn't have this problem until I switched to an electric fan and redid my gauges and I rewired everything 3 times to make sure that wasn't the problem
 

mikestang63

SN Certified Technician
Aug 27, 2012
9,911
6,693
204
In the garage
Are the original power wires hooked up? Yes or no
Did you use a dedicated 4 gauge power wire? yes or no
Add another 4 gauge ground from the chassis to the block? yes or no
 
  • Like
Reactions: jrichker

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
27,437
2,869
234
74
Dublin GA
lowendmac.com
Hi I have a 92 mustang LX 5.0 I have a new battery a new alternator (swapped to the 3g alternator) new ground strap and ground wire for the battery new gauges and it only charges to 11 volts has anyone had this problem and know a fix for it and I have went through 4 alternators still same problem (130 amp alternator and 200amp )
Alternator troubleshooting for 86-93 5.0 Mustangs:

Never, never disconnect an alternator from the battery with the engine running. The resulting voltage spike can damage the car's electronics including the alternator.



Revised 16-Oct-2016 to add 94-95 alternator wiring diagram

Red color text applies to cars with a 3G alternator.

Do all of these tests in sequence. Do not skip around. The results of each test depend on the results of the previous tests for correct interpretation.

Simple first step: Remove the alternator and take it to your local auto parts store. They can bench test it for free.


Use a safety pin to pierce and probe the insulated connectors from the rear when doing tests with the connector plugged into its' mating connector.

Engine off, ignition off, battery fully charged.
1.) Look for 12 volts at the alternator output. No 12 volts and the dark green fuse link between the orange/black wires and the battery side of the starter solenoid has open circuited.
3G alternator: Look for 12 volts at the stud on the back of the alternator where the 4 gauge power feed wire is bolted.
No voltage and the fuse for the 4 gauge power feed wire is open or there are some loose connections.

2.) Look for 12 volts on the yellow/white wire that is the power feed to the regulator. No 12 volts, and the fuse link for the yellow/white wire has open circuited.

Engine off, ignition on, battery fully charged:
1.) Alternator warning light should glow. No glow, bulb has burned out or there is a break in the wiring between the regulator plug and the dash. The warning light supplies an exciter voltage that tells the regulator to turn on. There is a 500 ohm resistor in parallel with the warning light so that if the bulb burns out, the regulator still gets the exciter voltage.
Disconnect the D connector with the 3 wires (yellow/white, white/black and green/red) from the voltage regulator.
Measure the voltage on the Lt green/red wire. It should be 12 volts. No 12 volts and the wire is broken, or the 500 ohm resistor and dash indicator lamp are bad. If the 12 volts is missing, replace the warning lamp. If after replacing the warning lamp, the test fails again, the wiring between the warning lamp and the alternator is faulty. The warning lamp circuit is part of the instrument panel and contains some connectors that may cause problems.

2.) Reconnect the D plug to the alternator
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see 2.4-2.6 volts. No voltage and the previous tests passed, you have a failed voltage regulator. This is an actual measurement taken from a car with a working electrical system. If you see full or almost full12 volts, the regulator has failed.

Engine on, Ignition on, battery fully charged:
Probe the green/red wire from the rear of the connector and use the battery negative post as a ground. You should see battery voltage minus .25 to 1.0 volt. If the battery measured across the battery is 15.25 volts, you should see 14.50 volts

Familiarize yourself with the following application note from Fluke: See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .



You will need to do some voltage drop testing of several of the wires.

Start looking for these things:
1.) Bad diode(s) in the alternator - one or more diodes have open circuited and are causing the voltage to drop off as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.

2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Do the voltage drop test as shown in the Fluke tech note link. Measure the voltage drop between the alternator frame and the battery negative post. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.

3.) Bad regulator that does not increase field current as load increases. Remove the alternator and bench test it to confirm or deny this as being the problem.

4.) Bad sense wire - open circuit in sense wiring or high resistance. The yellow/white wire is the voltage sense and power for the field. There is a fuse link embedded in the wiring where it connects to the black/orange wiring that can open up and cause problems. Disconnect the battery negative cable from the battery: this will keep you from making sparks when you do the next step. Then disconnect the yellow/white wire at the alternator and the green fuse link at the starter solenoid/starter relay. Measure the resistance between the alternator end of the yellow/white wire and the green fuse link: you should see less than 1 ohm. Reconnect all the wires when you have completed this step.

5.) Bad power feed wiring from the alternator. Use caution in the next step, since you will need to do it with everything powered up and the engine running. You are going to do the Fluke voltage drop tests on the power feed wiring, fuse links and associated parts. Connect one DMM lead to the battery side of the starter solenoid/starter relay. Carefully probe the backside of the black/orange wire connector where it plugs into the alternator. With the engine off, you should see very little voltage. Start the engine and increase the load on the electrical system. Watch for an increase in drop as the load increases. Use the Fluke voltage drop figures as guidelines for your decisions.

Alternator wiring diagram for 87-93 Mustangs.



The following are diagrams courtesy of Tmoss & Stang&2birds

Alternator wiring diagram for 94-95 Mustangs.


Voltage drops should not exceed the following:
200 mV Wire or cable
300 mV Switch
100 mV Ground
0 mV to <50 mV Sensor Connections
0.0V bolt together connections

Alternator wiring circuit
Notice the green wire connects to a switched power source. The circuit contains a 500 ohm resistor in series between the switched power and the alternator. Connecting it to switched power keeps the regulator from drawing current when the engine is not running. The resistor limits the current flowing through the wire so that a fuse isn't needed if the wire shorts to ground.

Also notice the sense wire connects to the starter solenoid and it is fused. It connects to the starter solenoid so that it can "sense" the voltage drop across the output wiring from the alternator.


Fuse link for 86-93 Mustangs
Replacement parts:
14 gauge fuse link for stock alternator.

Bussman BP/FL14 Fusible link
AutoZone

Dorman - Conduct-Tite 14 Gauge Fusible Link Wire Part No. 85620
Advance auto parts #85620
Pep Boys - SKU #8637594




See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring; http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

94-95 Mustang wiring diagrams
http://www.veryuseful.com/mustang/tech/engine/#95-95Diagrams

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

O2 sensor wiring harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangO2Harness.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Mustang 5.0 Lights and Radio schematic, by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxLights-Radio_diag.gif

87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif

93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif

T5 Cutaway showing T5 internal parts
http://www.veryuseful.com/mustang/tech/engine/images/5_Speed_Cutaway_Illustrated.jpg

Visual comparison of the Ford Fuel Injectors, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/Ford_Injector_Guide.jpg

Convertible top motor wiring http://www.veryuseful.com/mustang/tech/engine/images/mustang88VertTopMotorCkt.gif

Engine mounted fuel injector harness
http://www.veryuseful.com/mustang/tech/engine/images/mustangEngineHarness.gif

Location of the TPS, IAB, and the 10-pin connectors on a 5.0, picture by TMoss:
http://www.veryuseful.com/mustang/tech/engine/images/TPS_IAB_Pic.jpg

Starter circuit
http://forums.stangnet.com/attachment.php?attachmentid=21328&d=1080916057

Alternator diagram for 94-95 Mustangs.
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif
 
Thread starter Similar threads Forum Replies Date
J 1992 GT not pulling hard and misfiring Fox 5.0 Mustang Tech 3
voodoo18 1992 Injector question. Digital Self-tuning Forum 2
1 For Sale Original 1992 5.0 Owners Manual packet - Complete Packet Fox Body Mustangs For Sale (1979-93) 0
92NDSUgtFOX Engine Engine build questions 1992 GT Fox 5.0 Mustang Tech 14
voodoo18 1992 LX 5.0 mystery. use to run now doesn't. HELP Fox 5.0 Mustang Tech 43
J Bad wiring for fuel pump relay/constant priming? 1992 mustang gt Fox 5.0 Mustang Tech 8
S Fox Help finishing combo for 1992 GT 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 4
S 1992 2.3L NA no CEL 2.3L (N/A & Turbo) Tech 15
V 1992 GT Aftermarket radio-to-Stock radio/amp Mustang Sound & Shine All 4
9 Too much fuel ? 1992 5.0l Fox 5.0 Mustang Tech 21
M For Sale 1992 Fox Mustang Roller! Was on Pinks! Proven Car! Will Not Last!!! $6,900!!! Fox Body Mustangs For Sale (1979-93) 0
ppartain Electrical Random Stall Scenario 1992 LX 5.0 Fox 5.0 Mustang Tech 10
D 1992 GT Vert from NWI The Welcome Wagon 1
S Fuel 1992 351w Swap Fuel Pressure Issue/problems - Please Help! Fox 5.0 Mustang Tech 13
Lunysgwen 1992 363ci Foxbody PIMPxs first start-up questions Digital Self-tuning Forum 42
J Interior and Upholstery 1992 GT - Trunk release switch Fox 5.0 Mustang Tech 2
J Electrical 1992 GT - battery / stereo problem Fox 5.0 Mustang Tech 2
J Exhaust 1992 gt - flowmaster super 10 offset/offset vs. offset/center. whats the differences? Fox 5.0 Mustang Tech 5
Blucifer99 First start up using megasquirt.. 1992 5.0. Digital Self-tuning Forum 496
S Belt tensioner setup 1992 fox body Fox 5.0 Mustang Tech 10
1 Digital Tuning 1992 5.0 stock except 3G alternator and exhaust. Fox 5.0 Mustang Tech 9
S Project Resto - Supercharged 1992 GT 'Vert 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 150
J Paint and Body 1992 GT - gt tail lights "cheese grater" cover Fox 5.0 Mustang Tech 11
T Electrical 1992 after market radio + speakers back to oem Ford cassette radio Fox 5.0 Mustang Tech 7
J Fox 1992 GT - which exhaust setup? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 9
G Electrical 1992 GT fastback - running light issues Fox 5.0 Mustang Tech 2
J Fox 1992 window stutter 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 2
J Electrical 1992 gt horn not working Fox 5.0 Mustang Tech 2
1992 5.Slow GT Young owner of 1992 fox GT getting mild build, questions about tuning. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 5
M Convertible top 1992 mustang 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 4
A For Sale 92 Mustang LX 2.3L Automatic Convertible / Augusta GA / $2000 OBO Fox Body Mustangs For Sale (1979-93) 1
F Fuel 1992 Mustang GT 5.0- Fuel pump question Fox 5.0 Mustang Tech 3
Audiophile 1992 GT - Updated Audio System Mustang Sound & Shine All 0
1 Electrical 1992 5.0 Running rich with surging idle (surge checklist has been done) Fox 5.0 Mustang Tech 8
prgt347 Electrical 1992 w/ Codes 41 & 91 Fox 5.0 Mustang Tech 7
T 1992 foxbody W/502/t400 combo. Headers Question Other Auto Tech 3
8 Electrical 1988 2.3L EFI to 1992 2.3L EFI engine 2.3L (N/A & Turbo) Tech 2
3whtponies Electrical 1992 GT 5 speed Fox 5.0 Mustang Tech 2
F 1992 2.3L - engine fan not coming on, temp gauge not rising, A/C not engaging. Fox 5.0 Mustang Tech 1
9 1992 foxbody airbag light on Fox 5.0 Mustang Tech 2
Blucifer99 Engine 1992 mustang oil pan capacity with and without filter change Fox 5.0 Mustang Tech 22
C Engine 1992 codes 33 and 84 Fox 5.0 Mustang Tech 1
C 1992 foxbody Fox 5.0 Mustang Tech 2
L For Sale 1992 5.0L Mustang Convertible One Owner 8,700 actual miles Mint! Fox Body Mustangs For Sale (1979-93) 1
smokinbk For Sale 1992 Ford Mustang LX 5.0L Convertible Fox Body Mustangs For Sale (1979-93) 0
T 1992 Mustang GT 5.0 5spd Hatchback from Mid-Michigan!!! The Welcome Wagon 3
stanley514 Engine 1992 Fox 5.0 Mustang Tech 21
C New to me 1992 LX Cylspo Green The Welcome Wagon 2
AUBURN1111 1992 5.0L mustang MS2 PnP, heads, cam, intake. Idle with AC on? Digital Self-tuning Forum 50
R Engine 1992 Mustang Hesitation/Cutting-Out Fox 5.0 Mustang Tech 18
Similar threads