Electronics: Police interceptor High Output Alternator Upgrade

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Sep 12, 2023
Roselle, IL
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1994 Cougar XR7 DOHC TR3650
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Article provided by P71interceptor.

Below are some notes about installing a 200 amp mitsubishi alternator from a 2009 ford crown victoria police interceptor into a 1998 crownvic that originally came with a 135amp ford 6G alternator.

Here's the alternator we want to upgrade to.



This unit has about 10k miles on it and was in use for about a year before the car was wrecked.

In the northeastern united states, large quantities of chloride road salts are applied to the roads during the winter to melt snow and ice. And this how an alternator looks after just one new england winter.


The pulley on this alternator is clutched due to the high rotating mass of the alternator rotor. The one way clutch locks when rotated clockwise, but freewheels when rotated in the other direction. When car's engine is running, the alternator clutch will be locked most of the time, but it will freewheel during hard acceleration when the transmission shifts cause abrupt changes in the engine crankshaft rotation speed. It will also freewheel when the engine is shut off and the inertia of the heavy rotor keeps the alternator shaft spinning for a bit. Do note that this is just a "one-way" clutch and not an "overrunning alternator decoupler" (OAD) pulley like you'll find in some other vehicles.


There is a little surface rust on the pulley because the alternator sat unused for several months after the car was wrecked. This came right off after the alternator was installed in a car and run for a couple hours with the serpentine belt rubbing against the metal.


Here is the 200 amp tag on the alternator


Now let's take a look at the 135amp sixth generation (6G) ford alternator in the 1998 crownvic that we want to upgrade.


After removing the front engine accessory belt from the alternator



The alternator with the high current charging wire disconnected and the top mounting bracket removed


The alternator top support bracket from the top


The bracket from the bottom. The raised area in the bracket is to protect the fuel rail hose during a very high energy frontal collision.


Here are the 4 mounting bolts for the alternator


After loosening the bottom two mounting bolts, unplugging the regulator connector, and lifting the alternator out


Now that the alternator old alternator is removed, we can try to install the "new" one.


The alternator physically fits on the engine. But, the regulator wiring is too short to reach the regulator in it's new location due to the different location of the regulator connectors on the two different alternators.

Besides the physical length of the regulator wiring, there is also another hidden issue here of this late model alternator regulator being controlled with different electrical signals than this earlier model car generates. But for now, we are concentrating on the physical fitment issues of the alternator rather than the electrical control side.


Here are the two alternators side by side. Note the different location of the regulator connector.



Also, the opening in the ring terminal on the alternator output wire is too small to fit over the alternator output post stud.


The serpentine belt fits over the alternator pulley without any modification.


Also, the alternator top mounting bracket does not fit properly with the new alternator installed. Before the alternator bracket can be slid so that it's bolt holes line up with the alternator and intake manifold bolt holes, bracket hits up against the output charging post. A little work with a 4" angle grinder could likely fix this issue.


Another option is to use the alternator bracket that came with the dorman intake manifold kit. It's got more space open towards the back where the alternator output post is located.


The oem ford 6G alternator bracket next to the aftermarket dorman universal 3G/4G/6G bracket



This is a universal bracket for cars with 3G, 4G and 6G alternators. The 3g tab on the bracket comes a little close to the alternator, cutting this unused tab off would open up some space near the regulator.



Now lets remove the alternator output wire and enlarge the ring terminal with a 5/16" drill bit so that it will fit over the new alternator output stud. The old alternator uses a M6x1.0 stud on the output post, the "new" alternator uses a M8x1.25 stud instead.


Before modification


After modification

Now that the charging wire hole has been opened up, we can connect the alternator output wire and begin tinkering with the control aspects of the new alternator regulator.

This alternator will self excite without any regulator wires connected at all, but charging voltage will only be 13.6 volts under minimal load which is too low for good battery recharge characteristics. So we need to find some way to raise the voltage output of the alternator. My first idea was to use the alternators no-pcm-communication failsafe voltage setpoint and insert a diode or two inline with the voltage sense terminal to make the alternator think that the battery voltage was lower than it actually was.


In introductory electrical theory textbooks, you'll read that a diode always drops 0.7 volts across it. But in the real world, the voltage drop across a diode varies as a function of current and various other parameters. This causes the alternator output voltage to float around some as the car runs and things heat up. At first, i was only getting around a 0.4V drop across each diode, but later this started to ramp up close to 0.7V across each.


Maybe some high current diodes like those in a marine battery isolator could have solved the voltage float problem mentioned above or maybe a voltage divider consisting of a couple resistors could have been installed instead. But a cleaner solution is to send the alternator fake voltage setpoint data on the gencom line. This way, the alternator will think that it's installed in an actual car recieving voltage setpoint requests from the powertrain control module (PCM).

The 2003 and later crownvic alternators have a PCM controlled alternator regulator. There are two unidirectional control lines going to the regulator. The gencom line has information on it about what voltage the alternator should output. And the genmon line has information about what load the alternator is under, any problems the alternator may have, and various other operational data.


Unfortunetly, the 2002 and earlier crownvics control their alternators differently. The voltage setpoint inside the regulator is fixed and non-adjustable. And rotor field coil excitation voltage is obtained through the instrument cluster i-line to tell the alternator when to turn on/off the rotor magnetic field.


But if we place a 125Hz pulse width modulated (PWM) square-wave signal on the alternator gencom line of our "new" alternator, we can vary the alternator voltage setpoint by changing the duty cycle of the waveform.


A search for pwm circuit ideas revealed that there are a number of premade pwm circuits on the market catering to the HHO hydrogen generation crowd. The idea is that you can extract hydrogen from water which can then be fed through an automobile's engine air intake system to increase fuel economy. Many of these circuits were originally intended to control the speed of electric motors, but we can retask them for our alternator control project if they have an output frequency close to 125 Hertz and they are designed to control motor speed through the ground side of the circuit.

After looking at a few different circuits, i settled on the MX066 from bakatronics.



This circuit is based on the LM324 operational amplifier (opamp) and is designed to handle up to 30amps which is more than adequate for our alternator voltage regulator control application. The 100Hz frequency of this unit is somewhat close to 125Hz that ford generates inside the pcm to control the alternator. But if we want to raise the frequency of the pwm to 125Hz, we will need to lower the resistance of R4 in the circuit.




This circuit turned out to work very nicely to control the alternator even though the frequency of the pwm waveform is 25 Hertz slower then the ford gencom specifications in it's unmodified form.





For our project, we want to crimp three 1/4" spade terminals onto 3 peices of wire and insert them onto these tabs. We will be using the G, -M, and +12V terminals. The +M terminal will be unused since it jumps directly to the +12V feed and our alternator already has an internal source for +12V.

After crimping the wires and sliding them onto the circuit board




After inserting the circuit board into a case so that the traces don't accidentally short out against metal objects


The red wire is +12V, the grey wire is ground, and the white wire is the pwm output to feed the alternator gencom line.


Here's our testbed vehicle with the 2009 alternator installed. A new voltage regulator wiring pigtail was purchased, and one wire of the new pigtail inserted into the appropriate pin of the old regulator connector to read battery voltage. The middle gencom wire is connected to the output of the pwm device. Turn the pwm control knob counter-clockwise and we can raise the voltage setpoint of the alternator regulator close to 15Volts. Spin it clockwise and the setpoint will dip down below 12Volts at the other end of it's travel limit. The alternator voltage setpoint is very stable with batery voltage only varying +/- 0.01 Volts given a constant load on the car's electrical system.


Good battery recharge characteristics are obtained somewhere between 14.0 Volts and 14.5 Volts at a reasonable ambient temperature. The regulator in the factory installed 1998 crownvic alternator had a fixed setpoint of 14.4 volts according to transpo, but battery voltage was actually 14.1Volts at idle with the engine running and all accessories turned off according to my voltmeter.



This is a really powerful alternator that ford under-rates. If you spin the alternator really fast and the ambient temperature is low, you can get well over 200 amps out of this unit.


Here is a reference picture of a wrecked 2005 crown victoria engine with the alternator and it's wiring attached

(picture courtesy of Steve83 on www.crownvic.net)
Misc Notes:

Upgrading a 2003-2010 crownvic to this alternator would have been considerably easier since the powertrain control module (pcm) in these cars already generates a pwm signal on the gencom line. The pcm in the 1992-2002 crownvics does not communicate with the alternator at all other than the fact that it uses battery voltage for power.
A little lesson about the basics of an alternator: To get power out of an alternator, you first need to send power from your car's battery into the alternator to energize the rotor field windings. The rotor is basically a big elecro-magnet that creates a big magnetic field when electricity is applied to it. when the car is turned off, there is no power going to the rotor windings. In the pre-2003 crownvics, when you turn the ignition key on, battery voltage is applied to the rotor windings by applying +12V to the charge indicator lightbulb on your instrument panel, power then flows through the ~6 ohm bulb filaments to the regulator which then sends power to the rotor field windings to create a magnetic field. Once the engine starts spinning reasonably fast, the alternator begins to produce electricity in the stator coils which then turns off the charge indicator bulb by applying +12V to the bulb feed wire at the regulator. If both sides of a lightbulb are at +12V, the potential difference between the two sides is 0V and the lightbulb will not be lit.
There are two different ways for an alternator to self excite. Rotors usually have a small amount of residual magnetism in them and when you spin them really fast, it's sometimes enough to get sufficent magnetism induced into the stator windings to get the electricity out of the windings so that a full strength magnetic field can be built up and the alternator can output at full capacity. The disadvantage of this setup is that you often need to rev up the engine to get the alternator to self excite. But the alternator pulley is overdriven at about a 3:1 ratio by the crankshaft, and police interceptors have an initial cold idle speed of close to 1000RPM so the alternator shaft would be spinning at 3000RPM. The other method of getting the rotor magnetic field to turn on initially is to monitor battery voltage. A big drop in battery voltage indicates the starter motor was cranking the engine, and the rotor field coil can be turned on by the regulator for a couple seconds.
Instead of generating a fake gencom signal to simulate the pcm or sending an altered signal to the voltage sense terminal of the alternator regulator, you could in theory get one of these alternators working in an earlier car by hacking up the internal voltage regulator to pass the field coil signal to an external conventional i-line regulator. Many 1970's ford vehicles used such a voltage regulator setup, but you must be careful to make sure that your regulator can handle the load of such a large rotor field coil. Also, be aware that recent internally regulated ford alternators are a-circuit with rotor field current controlled through the ground side of the circuit. And most external ford regulators are b-circuit regulators with field current controlled through the positive side of the rotor field circuit.
The Alternator Regulator Pulls:
Voltage sense low (ground) (pin 1)
Genmon low (ground) (pin 3)
Gencom high (+12V) (pin 2)
This 2009 police interceptor alternator would self excite without any regulator wires connected.
Without the remote voltage sense pin connected, the alternator was in "machine sense" mode which sensed the voltage at the output post and commanded output 0.2V higher than in remote sense mode.
Conncting gencom to ground caused the alternator to stop charging or set the voltage setpoint really low
With no gencom pwm signal fed to the alternator, the genmon line would stay at 0V for a while, and then start sending a +12V squarewave signal to the gencom line, and then go back to 0V for a while and repeat the process. Connecting the charge light bulb on my 1998 crownvic's dashboard to this wire would not illuminate the light because this is a low current feed line not intended to drive a high current light bulb.
The alternator genmon line has a duty cycle of a little under 50% under minimal loading. And the duty cycle will increase as alternator load increases.
The 6G alternator regulator connector used in 1998-2002 crownvics does not have a wire in the middle pin of the connector. And the connector shell is not designed to allow installation of a new pin in this location either. To be able to send gencom data on pin 2, you will need to replace this connector with a new WPT-118 service pigtail from ford or one sourced from a wrecked 2003+ police interceptor donor car.
It can be rather frustrating on a high mileage 2003+ crownvic when the gencom or genmon wiring gets damaged and signals from other circuits get into these wires. Drive over a bumpy road and you might see your alternator charge at over 16 volts for a bit, then a while later drop so low that the car stalls out because the powertrain control module doesn't operate properly at voltages that low. If you suspect problems on this circuit, run a couple new wires from the pcm to the alternator regulator pigtail for the gencom/genmon signals. These are just signal wires that don't carry any real amperage, and 16AWG or 18AWG should be good.
Be careful not to leave the ignition "on" without the engine running when the using a pwm device to control the alternator. The pwm module will command the alternator rotor field coil to engage even though the engine isn't running. This will cause the field coil to generate a magnetic field and build up some heat too. When the engine is running, the alternator cooling fans are spinning to move air across the alternator components. When the engine is stopped, the cooling fans are also stopped, and the heat can really build up. You shouldn't have problems with this issue if you educate the drivers of your car not to leave the ignition on without the engine running. If you have your pwm device wired properly, turning the ignition key backwards to the accessory position to listen to the radio is fine, it's just leaving the ignition key in the run position without the engine running that is bad. If you are really adventorous, it's possible to wire the pwm circuit to monitor the engine oil pressure or fuel injector pulse rate to shutoff the field coil when the engine is not running.
The MaxxTronics pwm running with no load draws about 3 amps
The pwm components were cool to the touch after driving the alternator gencom lead for over an hour (even with pwm cooling fan disconnected). This is to be expected when one is running a circuit designed for thirty amps with only a few milliamps actually flowing though it.
The 200amp Mitsubishi alternator used in the 2004+ police interceptors costs about $500 from your local ford dealership. The ford 3G, 4G, and 6G alternator are about half that price.
The alternator pulley clutch in the 2004+ police interceptors often wears out before the remainder of the alternator components have failed. An alternator cannot charge if it's rotor is not spinning because of a defective clutch. Early warning signs of impending alternator clutch bearing failure include objectionable noises when the transmission shifts during hard acceleration or objectionable noises for a short period of time after you shut off your engine. The noises after you shut off the engine are because the alternator rotor has a decent amount of mass and continues to rotate, but the engine accessory belt holds the alternator pulley stationary causing the clutch to overrun.
The mxa066 pwm has linear control over the regulator voltage setpoint. At one end of the spectrum, the alternator charging output is effectively shut off because the voltage setpoint is so low. At the other end of the spectrum, the alternator output will climb close to 15 Volts. But there is an odd spot in rotating the knob after the voltage peaks at 15Volts. After that point, the voltage abruptly drops to 13.2Volts and stays there for the remainder of the rotation range instead of climbing higher. It is suspected that this is because the pwm is outputting 100Hz instead of the 125Hz that the alternator is designed to accept, and the alternator regulator goes to a failsafe setpoint at this point.
After installing the 200amp police interceptor alternator, you will want to upgrade the 6AWG charging wire and the fuselinks which protect the charging wire from overload. The factory installed 4G and 6G alternators use (one single 8AWG fuselink) or (two 12AWG fuselinks in parallel) for circuit protection. The police interceptor alternator uses two 10AWG fusible links in parallel, but a 300amp aftermarket ANL car audio fuse should work instead. Fusible link wires are basically very slow blow fuses constructed of specially designed undersized wire with extra thick insulation that can withstand very high temperatures. Do note that current flows in a loop and you need good ground wires too, but the factory installed ground wire is already rather thick because it carries the full load of the engine starter motor.
The output battery post stud on the 200amp mitsuibishi alternator is M8x1.25 which will have a diameter of approximately 8mm. To construct a custom charging wire, ideally you would use a metric #8 ring terminal lug on the alternator end. But, these are not readily avaliable and you will likely end up using an SAE 5/16" ring terminal lug from an aftermarket autoparts store, car audio shop, or marine boating supply store instead. 5/16 inches = 0.3125 inches = 7.9375 millimeters. Do not purchase an SAE 3/8" ring terminal lug because this is too large, 3/8 inches = 0.375 inches = 9.525 millimeters.
If you downgrade back to a ford 6G alternator, the output charging post stud is M6x1.0 which will have a diameter of approximately 6mm. To construct a custom charging wire, ideally you would use a metric #6 ring terminal lug on the alternator end. But, these are not readily avaliable and you will likely end up using a SAE 1/4" ring terminal from your local autoparts store, car audio shop, or marine boating supply store instead. 1/4 inches = 0.250 inches = 6.350 millimeters. If the mitsubishi alternator that you acquire has been rebuilt before, there is also a possibility that the alternator charging post will have an M6 stud instead of an M8 stud on it too.
The battery cable post that the alternator charge wire connects to on the underhood fuseblock of 1992-2002 crownvics is an M8x1.25 stud. Do note that the factory installed nut on this stud is odd in the sense that it limits travel of the nut on the stud. So you can install the M8x1.25 nut from a mitsubishi alternator onto this stud. But you cannot install the fuseblock nut onto a mitsubishi alternator because the indented area of the nut will grab against the alternator charging post stud threads before it can be tightened down enough to properly hold the charging wire in place.
The oem ford alternator output wire ring terminal lugs have a grey colored tin plating on them to protect against corrosion. The actual terminal underneath the coating is made of a copper alloy. In the aftermarket, ring terminal lugs are avaliable with and without the tin coating. And ring terminal lugs are usually located in the car battery or engine starter motor section of retail automotive parts stores. In the aftermarket car audio world, many ring terminal lugs come with gold plating appled to protect against corrosion. Gold and tin are both effective at preventing corrosion of the underlying metal, but some people prefer the cosmetic appearance of gold colored electrical components over the dull grey color of the tin plated ones.
It is also worth mentioning that a tutorial on crimping battery cable ends is avaliable here.
Some pictures of the fusible links that are located between the alternator output wire and the vehicle's battery on the 1998-2002 crownvics are avaliable on the battery cable harness webpage. Do note that the 1998-2002 crownvics are somewhat odd in the sense that the alternator fuselinks are not located in the charging wire that connects the alternator charging post to the underhood fuseblock, but rather in the wire that connects the fuseblock to the battery. In the 1992-1997 crownvics, the alternator fusible links are located in the charging wire which connects the alternator output post and the underhood fuseblock.
A technical service bulletin about retrofitting the 200amp mitsubishi high output alternator into a 2003 crown victoria is avaliable by clicking here. A special service message (ssm) from the ford oasis network about the powertrain control module calibration referenced in the previous tsb is avaliable by clicking here.
Some people may wonder whether it is possible to create their own kit to make installing a 2004+ police interceptor alternator into their civilian crownvic plug and play. This is possible, but it's also rather expensive. First, you need to acquire a 2004+ crown victoria police interceptor alternator, then you need to order the appropriate model year police interceptor battery cable harness (the alternator charging wire is part of the battery cable harness in 03+ crownvics). And finally, you need to order the little jumper cable extension harness which connects the alternator regulator to the connector on the car's electrical harness (part # 3W7Z-14A411-DA). Do note that you cannot use the 3W7Z-14A411-DA jumper harness on a 2003-2004 civilian crownvic, and would need to replace the entire fuel/charging electrical harness. But you might find it more cost effective to just cut-n-splice on a 1U2Z-14S411-TA (WPT-118) regulator pigtail onto your existing fuel/charging harness, and custom fabricate something for the high current alternator output wire instead.
There is programming information inside the powertrain control module specific to the alternator model that a crownvic originally had. But some people have upgraded their 2003+ civilian crownvics from the 4G civilian alternators to the high output police interceptor alternators by just splicing on a different alternator regulator pigtail and upgrading the output wire. And some police interceptors have had their 200amp mitsubishi alternators downgraded to the 135amp 6G alternators by just plugging in the new alternator. In both cases, no driveability problems were reported despite not reprogamming the pcm.
There has been some debate about whether the small electrical extension harness extension is really needed to install a 2004+ alternator into an earlier vehicle that's wired for the ford 6G alternator. Both alternators use the same electrical plug for the regulator, but the cars with the mitsubishi alternator have a longer regulator connector takeout than the cars with the factory installed 6G alternator do. Some people have said that they were able to stretch their fuel/charging wiring harness to reach the alternator regulator in its new location by disconnecting some harness->engine retainers and giving the harness a couple sharp pulls, but this is asking for trouble. Attempting to elongate an electrical harness by stretching the wires inside is going to damage the harness and could cause you nightmare electrical problems in the future.
There has also been some debate about whether the external control box for the alternator regulator is really needed when installing a 2003+ alternator into an earlier car. Some people are adamant they installed pcm controlled 2003+ alternator into an earlier car and it worked great without the external pwm box. While many 03+ alternator models will self excite and start charging if you install them in an earlier crownvic, they will only charge at a little over 13Volts. This is too low a voltage for good battery charging characteristics. The alternator might seem to work acceptably for a brief period during the warm summer months in a hot southern enviroment like florida. But you're going to have problems starting your car's engine during the winter months if you live in a cold enviroment like northern new england or canada. Good battery recharge characteristics are obtained somewhere between 14.0Volts and 14.5Volts. You can safely raise the charging voltage a little beyond that on really cold winter days too.
On internet discussion forums, you'll often see www.custombatterycables.com recommended for supplies to make custom automotive battery cables. There are also a handful of vendors location on www.ebay.com that sell similar supplies. Many people have also ordered automotive battery cable supplies from www.genuinedealz.com. This place caters mainly to the marine boating crowd, but their cable supplies work very nicely in an automotive enviroment too. Having battery cables that are really resistant to water and salt corrosion is a very good thing during the winter time in the northeastern united states. The local highway departments in this area of the country apply tons of chloride salts to the roads to melt snow/ice during the winter, and the engine bay of a car driven on northeastern highways during the winter will often look like a it has been operated in salt water marine enviroment.
TheShadow on www.crownvic.net commented "Does the Mitsubishi allow for a larger overall diameter ring to be used? I'd be a little leary about using an existing 135-amp circuit ring terminal and boosting the current through it so much, and having to decrease its cross-section at the same time. Possible work-arounds might be just adding a washer to match the extra size (if any), or using a thicker ring terminal." This is a very valid point. And in my case, the alternator was just connected for temporary testing purposes this way while I let the car idle in the driveway for a few hours with the hood open. Something else is going to be custom fabricated when the mitsubishi alternator upgrade becomes a permanent installation.
Wiring diagrams for ford crown victorias and mercury grand marquises are avaliable if you click here.
For possible mounting locations for the pwm: you could mount the pwm module to the driver's side of the rear seat strainer in the trunk, this is where the factory keyless entry module used to be mounted in the 1992-1994 crownvic lx's. On the 1998-2002 crownvics, there is also an unused location down low in the passenger's side a-pillar near the door hinges where the airbag crash module used to be located in the 1992-1997 crownvics. The technicians at your local car alarm and remote start installation shop can likely think of other mounting locations for you too, but you must not mount the pwm under the hood because this area has lots of water passing through and electronics are easily damaged by water.
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