Bad alternator?

[jdando]

Hey gang!

Just wanted to bounce a question off the group collective. I am seeing my volt meter flicker around erratically. With the subsequent dimming of lights, hvac blower, etc.

Would I be correct to assume the alternator is shot? Should I replace with the stock OEM unit or is there a "better"/more durable unit?

Thanks,

[musclemerc]

Before you replace it put a volt meter at the battery with the engine running and check for atleast 13.5V

[jus2rel]

I had an issue ever since owning my car with the volts dropping and spiking like crazy. It wasn't all the time but every now and then and especially when it got wet. When sitting at idle sometimes the volts would drop below 12 with no A/C or lights on to where the battery light would come on. I spent over $2000 having it diagnosed by multiple shops and dealerships with everyone saying the same bull*****. Everyone will tell you it is the alternator and voltage regulator or a bad ground. I left my car at the local ford dealership for a week and told the mechanic to take it home so he could see. He went through the entire car and inspected every ground to be sure none were loose. In the end they could not figure it out. The car still ran great but as you said at night it looked like I was flashing my lights. At its worst the volts jumped from 12-17 up and down like crazy, I thought the computer was gonna fry.

Long story short I finally skipped the dealers and mechanic shops I took it to an electrical shop, that is all they do. At first they told me my alternator and sold me that, but I knew it was the same old song and dance. I left and sure enough 10 min down the road it started again. I took it back and they sent all day testing all the wire.

It boiled down to either a wire that runs directly from the alternator to somewhere on the driverside of the firewall and the main computer. The computer was gonna cost at least $1000, but luckily they said the wire from the alternator was not creating a constant current. Somewhere within the wire was a break that was shorting out while driving. It made sense because the problem usually got worse over bumps and stuff.

I dont exactly remember what the wire was called or went to, but my advice is first replace the alternator to be on the safe side. If it still persist let me know and I will go back to the shop and ask them exactly what the replaced. If I get a chance I will take some pictures. Hope this helps.

[SpartaPerformance]

Most likely if the battery light doesn't come on then it's not the alternator. Check all your voltages first.

[BAD MERC]

Old-school trick: put something like a screwdriver behind the alternator while the car is running. A good alternator creates a magnetic field that will attract the screwdriver shank to the case.

[TooManyFords]

If anyone else has this problem, swap the voltage regulator out for one on the Mustang. It bolts right up and plugs in, but does not use the wire from the computer to control it. This also means it does not cut out at WOT, but will you really miss the .3 HP? I think not.

The cause is the chaffing of the wiring harness across the back of the motor that can also cause all sorts of weird failures. Mine eventually killed the starter circuit and the computer would reboot causing the tranny to go into neutral (ala MV VII).

Too bad there are no more looms available direct from Ford.

[jdando]

Thanks for the suggestions. I will look into this more today/this weekend.

[2vmodular]

the regulator you want was used in 2000-2002 civilian crownvics. you need a 4G alternator regulator to swap into your 2003-2004 marauder. a mustang 6G regulator won't physically fit in a 4G alternator.

below are a few alternator pictures to help you identify the alternator generation.


If anyone else has this problem, swap the voltage regulator out for one on the Mustang. It bolts right up and plugs in, but does not use the wire from the computer to control it. This also means it does not cut out at WOT, but will you really miss the .3 HP? I think not.

The cause is the chaffing of the wiring harness across the back of the motor that can also cause all sorts of weird failures. Mine eventually killed the starter circuit and the computer would reboot causing the tranny to go into neutral (ala MV VII).

Too bad there are no more looms available direct from Ford.

a 4G marauder alternator with the factory clutch.

http://www.p71interceptor.com/alternator/modelnumbers/8314/8314-4.jpg

http://www.p71interceptor.com/alternator/modelnumbers/8314/8314-3.jpg

a 4G crown victoria alternator without the pulley clutch

http://www.p71interceptor.com/alternator/modelnumbers/7773/7773-1.jpg

a 6G crown victoria alternator

http://www.p71interceptor.com/alternator/modelnumbers/7795/7795-1.jpg

http://www.p71interceptor.com/alternator/modelnumbers/7795/7795-2.jpg

[2vmodular]

running a non-pcm controlled voltage regulator in a later ford vehicle that requires a pcm regulator usually results in powertrain code:

P0622 (Generator Field "F" Control Circuit Malfunction)

i'm not sure whether the state emissions smog inspection stations can pick this code up or not. or whether you even have smog inspections in your area of the country.

[2vmodular]

i was playing with a recent pcm controlled crownvic alternator and was suprised to find that the alternator charged without the regulator plug connected at all. the battery voltage was 13.4V which is kind of low, but it did charge and the alternator did self excite without any external input on the regulator.

had you tried unplugging the regulator connector and starting up your car to see what the voltage would be. 13.4V would be a better than the 17V reading which is high enough to damage numerous electronic modules in your car.

[2vmodular]

here's an interesting document about how the pcm controls the alternator regulator:

http://www.p71interceptor.com/alternator/convert4g6g/pcmalternatorpdfs/techpoint1.pdf

and here's some info about a bench tester for these regulators:

http://www.p71interceptor.com/alternator/convert4g6g/pcmalternatorpdfs/pcmalternator5.pdf

[jdando]

Well I changed out the alternator and a few miles down the road the voltage started floppying around again :(

Took it to the local flaps and they tested it and said bad battery. Replaced with a genuine Motorcraft Battery.......and a few miles down the road and the voltage is floppying around again :(

I guess I need to start looking around in the wiring.

John; Can you expand on what happened with your car?

[2vmodular]

if you suspect problems with the wiring harness, i'd just run a couple new wires directly from the pcm to the alternator. cut the old wires a couple inches after the pcm and splice the new wires on. then cut the two genmon/gencom wires a few inches from the regulator plug and splice the new wires on that end.

the gencom/genmon wires are just signal wires that don't carry any real amperage per say. so lightweight stranded wire like 16AWG or 18AWG should be good.

[jdando]

Had a few minutes to look at the wiring today. With the Trilogy kit I had to extend both wires to the alternator. I checked the wires to the plug and I used crimp-connectors on those. One of the connections came apart with a gently tug :( I re-crimped it, so we will see if that solves the problem. I plan on soldering the wires this weekend. Stay tuned.

[2vmodular]

a little offtopic, but have any of you marauder owners tried upgrading to the 200amp police interceptor alternator?

http://images17.fotki.com/v529/photos/8/42438/8722459/PICT2936-vi.jpg

http://images56.fotki.com/v1600/photos/8/42438/8722459/PICT2953-vi.jpg

this unit has an overrunning clutch like the original equipment alternator in your car does. and it's a lot higher output which would be good for people with an aftermarket high power stereo system.

[2vmodular]

that 200amp mitsubishi alternator is controlled just like the original equipment 110amp 4G alternator in these cars. the gencom wire has voltage setpoint data on it from the pcm. and the genmon wire tells the pcm how much load the alternator is under and some other operational data.

here's my little pwm box to run this alternator in the earlier 4.6L cars without alternator support in the pcm. spin the control knob one direction and you get the voltage setpoint down below 12volts, spin it the other way and it goes up to around 15volts.

http://images56.fotki.com/v1598/photos/8/42438/8722459/PICT3440-vi.jpg

http://images19.fotki.com/v22/photos/8/42438/8722459/PICT3326-vi.jpg

[2vmodular]

if the wiring near the connector is corroded, service pigtails are avaliable seperatetly from your local ford dealership. the part # for the 2003-2004 marauder alternator regulator pigtail is WPT-119.


Had a few minutes to look at the wiring today. With the Trilogy kit I had to extend both wires to the alternator. I checked the wires to the plug and I used crimp-connectors on those. One of the connections came apart with a gently tug :( I re-crimped it, so we will see if that solves the problem. I plan on soldering the wires this weekend. Stay tuned.

http://www.p71interceptor.com/alternator/modelnumbers/wpt119.jpg

[Reek09]

My car has been doing the same thing. At times my voltage drops and goes back up when I Accelerate. It doesn't do it all the time, but when it does its annoying.

[fastblackmerc]

a little offtopic, but have any of you marauder owners tried upgrading to the 200amp police interceptor alternator?

http://images17.fotki.com/v529/photos/8/42438/8722459/PICT2936-vi.jpg

http://images56.fotki.com/v1600/photos/8/42438/8722459/PICT2953-vi.jpg

this unit has an overrunning clutch like the original equipment alternator in your car does. and it's a lot higher output which would be good for people with an aftermarket high power stereo system.

I'm going to install a 250Amp unit from DB Electrical.

[Zack]

My MM's have always dropped down to at or below battery voltage when its blazing hot and the AC is on Full Blast.

FYI there are 2 Fusible Links between the Main alternator Cable and the Battery.

[jdando]

Update;

After a week or so of running I have no voltage fluctuations! It is nice to have full voltage available for driving the AC fan this past week of pre-summer heat and humidity!

[Sully008]

Had a few minutes to look at the wiring today. With the Trilogy kit I had to extend both wires to the alternator. I checked the wires to the plug and I used crimp-connectors on those. One of the connections came apart with a gently tug :( I re-crimped it, so we will see if that solves the problem. I plan on soldering the wires this weekend. Stay tuned.

Soldering larger gauge wires can be a pain. I suggest using the Gardner Bender splice kit:

http://images2.cableorganizer.com/gardner-bender/butt-splice-kits/butt-splice-kits.jpg

I used them on my Trilogy install and they work great. I picked it up from Home Depot.

[J.bo]

My MM's have always dropped down to at or below battery voltage when its blazing hot and the AC is on Full Blast.

FYI there are 2 Fusible Links between the Main alternator Cable and the Battery.

Is your problem solved?

[Zack]

Is your problem solved?

Not that I know of, but I havent looked into it either.

[2vmodular]

the ford motorcraft wiring pigtail kits include a couple crimps and a couple peices of adhesive heatshrink tubing. these splices have very good durability even after being through a few salty new england winters.

that gardner kit from home depot looks like it has heatshrink tubing in it. but does the heatshrink tubing have adhesive inside that fills up the splice to keep water out?


Soldering larger gauge wires can be a pain. I suggest using the Gardner Bender splice kit:

I used them on my Trilogy install and they work great. I picked it up from Home Depot.

here's a picture of a ford motorcraft blower resistor pigtail kit showing the splice materials in question.

http://www.p71interceptor.com/blowerresistor/replace/PICT3451.jpg

http://www.p71interceptor.com/blowerresistor/replace/PICT3451-vi.jpg

[2vmodular]

i've seen aftermarket alternators that subsituted a regular solid metal pulley in place of clutched pulleys. when you purchase your alternator, look closely at the pulley. also do be aware that the marauder 4G alternator does not have as much airflow through the case as the ford 6G or mitsubishi police interceptor alternator. this can be a problem if you're actually pulling a lot of power out of the alternator because you'll generate a lot of heat in the process. and heat kills electrical components.

also, i was discussing the 2004+ police interceptor alternator upgrade with owners of lincoln mark viii's. these cars have dohc engine like the mercury marauder does. one point mentioned is that clearance towards the back of the alternator is more limited than in sohc engines. and the police interceptor alternator is deeper than the ford 3G, 4G and 6G alternators. so there might be a clearance issue. the pulley also extends further forward, so you'd have to watch the clearance around the coolant pipe that runs in front of the alternator.


I'm going to install a 250Amp unit from DB Electrical.

http://www.p71interceptor.com/alternator/modelnumbers/11026/11026-9.jpg

[2vmodular]

the interior blower motor & a/c condenser fan are a huge electrical load. some voltage drop is normal.

if you want to see your voltage dip really low, crank the a/c fan up and turn on the rear window defroster. during extended idle with all these accessories on, the voltage can dip so low that electronic modules like the lcm start misbehaving.


My MM's have always dropped down to at or below battery voltage when its blazing hot and the AC is on Full Blast.

those fusible links are to protect the alternator charging wire in case metallic debris accidentally touches an exposed portion of the harness. the fuselinks also protect against fire in case the alternator rectifier diodes short to ground.

if you are worried about the fusible links causing voltage flucations, you can measure drop using a volt meter with one terminal connected to the alternator charge post and the other connected directly to the positive battery post. voltage drop should be less than 0.1V with a decent load on the electrical system.


FYI there are 2 Fusible Links between the Main alternator Cable and the Battery.

[2vmodular]

if you are getting battery voltage readings over 16V, you're problem is caused by the alternator regulator or something with the voltage sense terminal that connects to the regulator. even at maximum duty cycle, the gencom wire going from the pcm to the alternator can only request a max of 16V.


My car has been doing the same thing. At times my voltage drops and goes back up when I Accelerate. It doesn't do it all the time, but when it does its annoying.