Electrical Alternator (91 Mustang GT & 89 Lincoln Mark VII)

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
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Appreciate this. Been having fun with my son at the junk yard (we call it the alternative parts store).
Ok, here's what you'll want to grab. I'm going to assume that Cobras are rare or non-existent at your yards so this will be a good brake system built on mostly V6/GT parts.


Front:

Spindles off 94-95 Mustang (any model).
Dust shields off any 94-04 mustang
Rotors off any 94-04 Mustang V6/GT
2-piston Alum calipers off a 99-04 V6 Mustang
Pair of front brake lines off 99-04 Mustang

Rear:
Pair of 5-lug axles off a 94-98 Mustang V6 or V8

Brake parts can come from any 94-04 Mustang. They are all the same but the main difference is you cannot use the 99-04 axle shafts. You want
-Calipers, rotors, axle brackets, anti-moan brackets, dust shields
-Parking brake cable guides that are bolted to the sway bar bracket


Booster:
Any 94-95 Booster, or 99-04 V6 vacuum booster. Avoid the 96-98 v6 vacuum boosters. Avoid a booster where a leaky MC caused the front under the MC to corrode. If any brake fluid gets on the rubber, it will deteriorate and leak. DOn't take the risk due to the PITA job of swapping these. May be advised to go reman here.

MC. Ideally you want a 1.00" bore here for this setup. That means 1993 Cobra whick you'd have to buy new. You can snag a 1999-2004 V6MC which is also 1.00" bore, but the fitting sizes are unique so you'd have to make the lines. You can TRY a 94-95 V6/GT master cylinder which is 1 1/16" bore, but the pedal might be a tad bit too firm for your liking.


Misc. You'll need to buy a few additional items, such as e-brake cables. , Adjustable prop valve, and the prop valve plug.

Here's your basic instruction manual.

http://static.summitracing.com/global/images/instructions/fms-m-2300-k.pdf
 
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Jhp84

Member
Mar 2, 2019
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Ok, here's what you'll want to grab...

Here's your basic instruction manual.

http://static.summitracing.com/global/images/instructions/fms-m-2300-k.pdf
Been talking it over with my son. He's thinking about keeping it as original as possible, with the four lug rims (see picture). I suggested that he at least consider rear disc brakes. Are there any vehicles that you suggest we pull parts from to go with this option?

By the way, the tires are old (we know they are at least eight years old because the car was in my friend's driveway not running since 2010). Front driver's tire leaks. For now, we thought we could grab two tires from my brother for free (205/70R15). That's when noticed the car currently has a set of 225/65R15 tires. Any issues with this difference? Also, we noticed neither configuration matches what is posted on the door frame (see picture). So now we are debating what configurations we could go with if we kept the original wheels. Want to keep the price reasonable but also want to ensure my son is safe on the road.
(He says he won't be foolish and race around town, but he's 18 years old. I remember what I did at his age. So, I have to mindful of his safety.)

Back on the alternator issue. We replaced the original with a 6G from a 2003 V6 Mustang. Had it checked at O'Reilly and also at Autozone. Both confirmed alternator was putting 14.6 volts. However, the battery continues to drain so we did a parasitic leak check. No issues there. Then we checked the voltage at the battery with engine off (12.3 V). But, the voltage from the power output plug on the alternator to the negative post on the battery read 11.8V, and from the alternator power to the chassis-block ground also read 11.8V. We ran a four gauge line from the alternator to the battery, from the engine to chassis ground, and from the negative post to the chassis ground. We left the pulley from the 6G alternator on as directed in an earlier post. Where did we go wrong?

Thx, jhp
 

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Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,743
7,941
224
Massachusetts
Been talking it over with my son. He's thinking about keeping it as original as possible, with the four lug rims (see picture). I suggested that he at least consider rear disc brakes. Are there any vehicles that you suggest we pull parts from to go with this option?
1987-1988 Thunrderbird turbo coupe.

Grab all the same rear parts as listed above. Take the axle shafts and all the brake hardware. It's basically a 1993 cobra rear setup. Grab a 94-95 or 99-04 v6 booster. You'll need to buy a 1993 cobra master cylinder.



By the way, the tires are old (we know they are at least eight years old because the car was in my friend's driveway not running since 2010). Front driver's tire leaks. For now, we thought we could grab two tires from my brother for free (205/70R15). That's when noticed the car currently has a set of 225/65R15 tires. Any issues with this difference? Also, we noticed neither configuration matches what is posted on the door frame (see picture). So now we are debating what configurations we could go with if we kept the original wheels. Want to keep the price reasonable but also want to ensure my son is safe on the road.
(He says he won't be foolish and race around town, but he's 18 years old. I remember what I did at his age. So, I have to mindful of his safety.)
Your wheels aren't original. You should have the 16" 5-star pony wheels with the 225/55/16 tires on them. The 4-cyl got the 15" wheels as an option with the 205's. The V8 Mustangs originally equipped with 15" wheels (up to 1990) got 225/65/15's. The sticker is accurate for your year based on the options available, but your car isn't wearing the correct original wheels.


Back on the alternator issue. We replaced the original with a 6G from a 2003 V6 Mustang. Had it checked at O'Reilly and also at Autozone. Both confirmed alternator was putting 14.6 volts. However, the battery continues to drain so we did a parasitic leak check. No issues there. Then we checked the voltage at the battery with engine off (12.3 V). But, the voltage from the power output plug on the alternator to the negative post on the battery read 11.8V, and from the alternator power to the chassis-block ground also read 11.8V. We ran a four gauge line from the alternator to the battery, from the engine to chassis ground, and from the negative post to the chassis ground. We left the pulley from the 6G alternator on as directed in an earlier post. Where did we go wrong?

Thx, jhp
With engine off, you will read battery voltage (or close to it) on every power line you check. What's voltage on the battery with the engine running? Should be 14-14.4 volts above idle?

If you have a multimeter capable of 10Amps DC current, remove one lead from the battery and measure in series across it. How many amps do you see being pulled? Should be very low...0.01amp or so.
 

Blown88GT

Founding Member
Nov 13, 1999
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...By the way, the tires are old (we know they are at least eight years old because the car was in my friend's driveway not running since 2010). Front driver's tire leaks. For now, we thought we could grab two tires from my brother for free (205/70R15). That's when noticed the car currently has a set of 225/65R15 tires. Any issues with this difference? Also, we noticed neither configuration matches what is posted on the door frame (see picture). So now we are debating what configurations we could go with if we kept the original wheels. Want to keep the price reasonable but also want to ensure my son is safe on the road.
(He says he won't be foolish and race around town, but he's 18 years old. I remember what I did at his age. So, I have to mindful of his safety.)
...
Turbine wheels are not original to '91's.
The turbines were not well liked because they were so difficult to clean.
I couldn't even give mine away. Still have them.
91's had a 16x7 in wheel. The turbine's are 15x7 in.
OEM tire was 225/60-15 or 225/55-16 which have the same diameter (or circumference).
'87-89's had clearance issues with the OEM tire size.
Find something close with this tire size calculator
https://www.tacomaworld.com/tirecalc
I have 225/50-15's on the turbines, 15x7
Also have 225/50-16's on the aftermarket 16x8.
Used to have 245/45-16 but couldn't find them when needed a replacement.
 

Jhp84

Member
Mar 2, 2019
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11
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california
1. Thanks on the info for the brake upgrade. Will keep our eyes open at the yard.

2. Disappointed to hear about the wheels. Thought the car was complete. Will check with my friend to see what happened with the pony wheels.

3. With the car running, voltage across the battery drops down to 11.88V at idle. Same if we rev the engine. Nowhere near 14V.

Yes, checked the amp in series with engine off and it read 0.01Amps.

Also took off the 4-gauge power line from the alternator to read voltage between the power out post and the negative terminal. Not sure if this is correct, but came up 8.3V, with the engine off.
 

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,743
7,941
224
Massachusetts
Sounds like the alternator is not outputting, or being told to output. What connections do you have on it? Power wire and what else?
 

Jhp84

Member
Mar 2, 2019
75
11
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california
Sounds like the alternator is not outputting, or being told to output. What connections do you have on it? Power wire and what else?
Just the power wire and the connector
Sounds like the alternator is not outputting, or being told to output. What connections do you have on it? Power wire and what else?
Just the power wire and the regulator plug (green and yellow wires). Nothing else.
 

jrichker

StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
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Just the power wire and the connector


Just the power wire and the regulator plug (green and yellow wires). Nothing else.
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 28-Nov-2018 to add warning that the instrument cluster must be in place and working for the alternator to charge

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.) The alternator MUST have the instrument cluster in place and working properly. The alternator warning light is a part of the charging circuit. The alternator warning light should glow. No glow, bulb has burned out or there is a break or bad connection in the wiring between the regulator plug and the instrument cluster. 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
https://www.stangnet.com/mustang-forums/attachments\21328

Alternator diagram for 94-95 Mustangs.
http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif
 

Jhp84

Member
Mar 2, 2019
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11
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california
You folks are great! Problem resolved. We had disconnected the green wire from the starter solenoid to the alternator after we soldered the white and green wires from the 6G alternator pigtail to the regulator and instrument panel leads. We didn't realize that this still needed to be connected; one of the replies to an earlier inquiry suggested this could be ignored. Nope. Needs to be there. It's reading 14.6V. Beautiful.

Noticed the power steering pump and hoses are wet and that the radiator support is bent in the middle underneath. Doubt it is supposed to look this. We think someone previously attempted to raise the vehicle here. Your thoughts on how to fix?
 

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Blown88GT

Founding Member
Nov 13, 1999
1,688
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You folks are great! Problem resolved. We had disconnected the green wire from the starter solenoid to the alternator after we soldered the white and green wires from the 6G alternator pigtail to the regulator and instrument panel leads. We didn't realize that this still needed to be connected; one of the replies to an earlier inquiry suggested this could be ignored. Nope. Needs to be there. It's reading 14.6V. Beautiful.

Noticed the power steering pump and hoses are wet and that the radiator support is bent in the middle underneath. Doubt it is supposed to look this. We think someone previously attempted to raise the vehicle here. Your thoughts on how to fix?
This was part of my website writeup:
DO NOT remove the existing 10AWG black/orange wire (connects to a green fuse link) from the starter relay. The yellow/white wire (connects through a brown fuse link) connects through the green fuse link and is needed for proper regulator control.

It's shown here, doesn't show the fuse needed on the 4AWG charge wire.
Later alternators have the stator wire bridged internally.
EVTM_p012a.jpg
 

Jhp84

Member
Mar 2, 2019
75
11
18
california
I would replace that lower piece of the core support.
Been looking up videos on replacing the radiator support. The ones we have seen show removing the front end: bumper cover, side panels, and radiator support to drill out welds. They then replace the support by welding in a new one. Is there another way? If not, then I guess we start learning to weld, since I am not too familiar with welding and would likely have to borrow the equipment. Might slow things down a bit, but that's okay. Having a blast with my son.

Thx, Jhp
 

Mustang5L5

This is a big reason why I pulled it out
Mod Dude
Feb 18, 2001
31,743
7,941
224
Massachusetts
Id start by just pulling the radiator out and seeing if you can move that back to the original shape by "creative means".
 

Blown88GT

Founding Member
Nov 13, 1999
1,688
317
124
Palm Beach Gardens, FL
Id start by just pulling the radiator out and seeing if you can move that back to the original shape by "creative means".
I agree. It actually looks pushed in from the front rather than bent up from the bottom. I don't use the standard mounting location, moved the bottom of the radiator in to gain clearance for the SC tensioner & larger SC pulley. You can see where the lower mounting pads used to reside.
IMG_1056.JPG
 

Jhp84

Member
Mar 2, 2019
75
11
18
california
Got back to the car this weekend. Been looking at the bottom of the vehicle and noticed the car has been jacked up (lifted) in all kinds of different places. Didn't really see anything that would suggest front end damage. Given the number of places that appear crushed underneath, we are pretty sure the radiator support is bent because they lifted the car here.

Seems they even tried lifting the car from under the driver's seat. Noticed that the driver's seat leaned to the left not the typical right (inside) side. Looked under while my son sat in the car and I could see there was a crack in the floor pan. Wondering if we can get by with installing subframe connectors with seat supports. Or, if we need to have the floor pan welded (and then add the subframe connectors).

As we may have mentioned earlier there is a lot of grease, oil, grime (and spider webs) under the front. We noticed that there is a metal tube on the rack and pinion that is disconnected. Thought about reconnecting it but the rubber housing (female side) seems deteriorated. Can this be replaced separately? Or is it an integral part of the real and pinion?

We thought about doing a transmission fluid flush but we have heard from others that this is not a good thing to do, that we should simply change the transmission filter and gasket. Is this true? The car has been idle for ten years. Wouldn't it make sense to replace the transmission fluid entirely?

Lastly, we see two drain plugs on the oil pan. One is up front, the other is further back.

Thanks, jhp
 

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