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MaxiFuse

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fordsvt98

Veteran CEG'er
Joined
Jul 8, 2004
Messages
665
Location
Minneapolis, MN
10.8 volts and dropping when my vehicle is running....to the point of dash lights no workie, tach falls to the pin, radio dies, I was driving and then its like it wants to die, I had to feather the gas pedal home, wierd ummm........Battery seems to not be charging, does maxi fuse line run to Batt or to Alt? If i put voltmeter on the red lead on the maxifuse what am I reading: to or from the batt? If my Maxifuse is GOOD and reading 0, the next thing responsible for charging the battery is the Alt right? Is there a possible fuse blown that would prevent proper Batt charge? Or Alt performance? Thanks. Stumped. Tools on the ready for weekend Alt change Im thinkin'. Just would like chime in from someone anyone as a second opinion.....before i start dissasembly....please...

1. Where does Maxifuse line go?
2. Assuming Maxifuse is good, at 0, next step would be Alt?
3. Any fuses hindering batterycharge?
4. Is there a fuse for the alt?
5. Any second opinions please! Thank you.
 
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Properly diagnose the problem:

charge your battery fully using a charger.

once charged, check the voltage while running (at the battery terminals) The voltage should 13.8-14.2 (+-.2) VDC. If not, suspect alternator, wiring, or mega-fuse.

Check your battery voltage:
Shut off the car, turn on the headlights for 60 seconds, and then test the battery voltage. It should be 12.0VDC or higher. If not, suspect battery.

The megafuse is in series between the alternator and the battery positive terminal. It is located along the firewall, underneath the coilpack. Check the "alternator removal" how-to in the Duratec Maintenance forum for pictures of this location.

To test the fuse, test the resistance of the fuse, across the two terminals of the fuse. Place your multimeter in "ohms" mode (lol) and place the two leads on either side of the fuse. You should get a 0.00 and/or a beeping noise, similar to the results you get it you simply touch both multimeter leads together and see what happens.

If the fuse is good, and your battery voltage test proves good, suspect the wiring either from the alternator to ground, alternator to megafuse, megafuse to battery (+), or battery (-) to ground.

Also, check your foglight fuse, as the alternator charge is controlled by this fuse in later models.
 
Wich way is the Maxifuse line current going? to the battery or, is it from the batt to the alternator, just for kicks, I was just wondering... anyone? ray?
 
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Ya, umm is the Maxifuse line the one charging my battery? Heres what happened today, I charged my battery...I was at 14.4 and holding, then I turned all my acc on, heat, fogs, lights, defroster, and it was at 13.1....and rose up to 14.1 when i hit the pedal a wee bit...so I shut the engine off, and started it again.....I must have drawn the volts out of the battery, now my volts are dropping again like the battery is not getting a charge, 10.6 .5 .4 .3 2 1 ......then i I get my LOW VOLT indicator....So it seems my battery is not recieving a charge....my 2 questions are, 1. is the maxifuse line the one that is charging my battery from the alternator? If it is, and Maxifuse is good, Im gonna slap in an alternator...or, 2. my other question is, what line can I volt-meter, directly off the alternator to see if its pumping out juice? Im assuming the fat dog red one right?? i havent jacked up my car yet.....but Im goin out there again later with my jet heater.....stupid questions I know but hey, I havent took my meds yet.
 
Oh just great. I have a mouse problem. Lil poops in my battery shield cover, Ive got rags for the dipstick in there, and theres holes in my rags. JUST GREAT. Any mouse exterminators in here recommend a good poison? I wonder if he chewed thru a wire. Oh man. HELP.

Ray said: The megafuse is in series between the alternator and the battery positive terminal. It is located along the firewall, underneath the coilpack. Check the "alternator removal" how-to in the Duratec Maintenance forum for pictures of this location. I know where it is....just tell me what it does please. In other words what Im trying to ask is: this Megafuse wire, is the one that charges my battery right?
 
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No.. the alternator charges your battery, to be specific.

If you read what I wrote, you will see exactly where the charge comes from. It comes FROM your alternator, through the megafuse wire along the firewall, to the battery(+) out the batter(-) through the chassis, and back to the alternator.

EDIT: actually, to be specific, the electrons travel from negatvie TO positive, but still.. yes.. the wire with the megafuse is what allows the charge to get from the alternator to the battery. Why would they place a fuse on a wire that was irrelevant?
 
The fuse is a fuse, not a diode. It is not a one way flow device. The fuse protects electrical components and wiring when there is a meltdown. In this case, the main protection is if the diodes in the alternator short out, the fuse will blow before it burns up the wire to the battery or starts a fire.

If the maxifuse is blown, the alternator will not charge the battery. The B+ wire that the maxifuse is located in is the main line from the alternator to the battery. The name B+ wire means that it connects to the battery positive post. The other wires to the alternator have to do with controlling the alternator through the integral voltage regulator.

If the fuse is blown, there is a posibility that the alternator has a problem, as fuses seldom fail from old age, but usually from an electrical overload.

With all that said, I'm still most suspecious of the BATTERY. Substitute a known good battery from another car long enough to run the test again. An intermittant internal open in the battery could explain all your problems.

If you had over 14 volts on one of your tests, the fuse is fine, and the alternator was working, at least for those few moments.
 
This is a very good point. Fuses aren't intermittent, at least not in the 999,999,999 out of a billion times. Once they blow, they're blown.

If you ever got 14volts when running, the fuse is (or was?) good at that time.

If the charge stopped, the alternator stopped producing a charge, the wiring came undone/is intermittently attached, the battery is faulty, OR the fuse JUST blew (after your last test)
 
Oh Understood completely, my question was "is the maxifuse line the one charging my battery?" and it probly splits a time or two before it gets to Batt+, but I get the gist of it now... that has been more than answered by both of you, thanks! I appreciate that! As far as the fuse intermittently working, Fat chance in hell that this happens, but, Ive bee reading a couple post's that they claim their maxi fuse was working "on a thread" type of basis..now all of them the end result was, they replaced the fuse. (of course)(I have yet to yank my Coilpack and peek in there but I will soon to check) its cold this weekend!... I understand that the batt would recieve a slight charge in these "hanging by a thread" circumstances, but, I do not feel that I am in this catagory at all. Either A. The Maxifuse is blown....or B. my alt is crapped out. Fogs n 15a fuse are in primo condition, My deal is, My alt crapped on me overnight it seems, Yesterday was working fine, today, no charge! I was in the field of "this kinda thing can't happen overnight" but, I guess maintenance items dont "always" give you a warning sign. I'll be sure to post my results when Im done for sure...but Its just too damn cold up here in MN ! Thanks for your input guys. Now when I start my car, and go to Voltmeter my Alt, if it aint puttin' out 14v at the MAXILINE I know that bad boy is crapped out.....or one of the three harness plugs is off, I think its Grey: ground Red: uhhh 12v Bl/Gr: dash light... or that ground strap is off possibly? Looks like the ground strap that goes from alt to the coil pack by the pictures i seen....but I will check when I get out there....someday....when it warms up.....brrrr.
 
Ray: If you read what I wrote, you will see exactly where the charge comes from. It comes FROM your alternator, through the megafuse wire along the firewall, to the battery(+) out the batter(-) through the chassis, and back to the alternator.

Oh, I didnt see that up there thats why I asked....I know you know what youre talkin about, but I dont, so I had to ask again cause I couldnt make out that specific wording/help out from your original post, no biggie....you still the man. And I appreciate any letter you put down on your keyboard to help a fellow contour person in need! (cause I need it right now lol)! and you too Big Jim thanks!

Oh and I had 14v but that was when my battery was charged so much juice was spillin out the sides, then I thought my problems were solved magically.....but then I tried to start my car again, and it really bit off that surface charge and I was back to 11v again lol! Then I said to myself, maybe magicians are fake! and I wished I had a trick up my sleeve lol.!
 
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The Maxi Fuse is directly in line between the battery and the alternator.

And trust me, this could still be a BATTERY problem. I've been there MANY times. You have not qualified the battery yet.

Your drop to under 12 volts on a seeminly charged battery is possible with an alternator problem, but far more likely to be a BATTERY problem. If you have an intermittant open between cells in the battery it will act intermittantly EXACTLY how you have described.
 
Ya im gonna go exchange it..maybe its not taking a charge, but, shouldnt I be getting 14v at the terminals at least (if the alt was working,and/or maxi was good of coarse)...my dad was from the old school, and was like: "take + off the battery when its runnin'"....i was all like "hold up pops....were in the new school now brotha." I was metering at 2 places, the batt, and my cig lighter..... neither gave me even 13v....both gave me 11.6 max.....so Im leanin towards the Alt......I didnt yank the coil pack yet..but I bet that fuse is good, but I WILL NOT replace my Alt till I check the Maxi, and the harnesses on the alt. And have a dead line from the Maxi. Then Im gonna go in and get Alt tested. Then....I will purchase. Other than that it MAY be wires....I hope so at least....Ill update when I get out there. Thanks guys. This happened after I put in this new rear roll resistor, I think I shouldnt have put it in, it vibes bad, This SVT gave me 4 years of love....the least I can do for my baby is throw 150 bucks at it. She's so worth it.
 
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fordsvt98 said:
.... This happened after I put in this new rear roll resistor, I think I shouldnt have put it in, it vibes bad, .....
Click to expand...

I would check all wiring and connections first. Then I would test the aternator and suspect the voltage regulator if the alternator tests bad. Too much vibration is not good for the connectors and VR.
 
fordsvt98 said:
but, shouldnt I be getting 14v at the terminals at least (if the alt was working,and/or maxi was good of coarse)...my dad was from the old school, and was like: "take + off the battery when its runnin'"....i was all like "hold up pops....were in the new school now brotha." I was metering at 2 places, the batt, and my cig lighter..... neither gave me even 13v....both gave me 11.6 max.....so Im leanin towards the Alt......I didnt yank the coil pack yet..but I bet that fuse is good, but I WILL NOT replace my Alt till I check the Maxi, and the harnesses on the alt. And have a dead line from the Maxi. Then Im gonna go in and get Alt tested. Then....I will purchase. Other than that it MAY be wires....I hope so at least....Ill update when I get out there. Thanks guys. This happened after I put in this new rear roll resistor, I think I shouldnt have put it in, it vibes bad, This SVT gave me 4 years of love....the least I can do for my baby is throw 150 bucks at it. She's so worth it.
Click to expand...

You will ony get 14+ volts if the battery is good and the alternator is working properly.

Disconnecting the battery while the engine is running is a good way to screw up electronics. And you may not know immediately that you did. You might not do any damage, but the likelyhood of doing some is too much.

Back to basics.

Charge and test the battery. If there is any doubt about the battery, have it tested at a shop or parts store. There is no definitive test for a battery. It may test perfectly and still be a problem although that would be rare. It still happens. I've been bit more than once.

Once you are reasonabley sure of the battery, take a volt reading accross the terminals. Apply a light load first to take off any surface charge (lights on for about 30 seconds for example). You should read well over 12 volts. Probably 12.5 or 12.6 and a really strong battery. This is your base voltage reading.

Start the engine and hold the engine speed up at about 2000 RPM and read the voltage again with no electrical accessories on (heater, lights, A/C, radio, etc.). It should be between .5 volts and 2.0 volts higher than the base voltage. The more fully the battery is charged, the higher the voltage reading.

The readings you are getting part of the time do not indicate a bad fuse.

The readings you were getting of way less than 12 volts with the engine running (with no electrical accessories on) can happen only if there is a sudden large electrical load (alternator shorting) or a flakey battery. Shorted alternator diodes don't usually correct themselves. Even if the dead short is momentarily relieved as the shorted parts seperate, the voltage output would be dramatically dropped. Unless there is a huge drain, you will not drop below the base battery voltage reading.

An intermittant open in the battery can and will drop the battery voltage clear down into the 6 volt to 8 volt range.

With what you have described I would substitute a known good battery and test again. You do what you want. I'm through here.
 
Swapped the ALT today. I was broke down, but I pulled thru it with a friend! Man, whoever thought that design up is cursed for life from all my swearing lol.
-Bottom 13mm Alt bolt was a straight shot w/ 2 9" extensions that was nice. Had a copious amount of room to hit that bad boy I was amazed. finally i found that sweet spot that needed no swivel. I was perplexered for wee bit there whooooo lemme tell ya's
-Lil swivel on that Bracket 10mm Bolt and she popped right off.
-Top ALT BOLT! OMGGGGGGGG what a PAIN.
for the Top Alt Bolt...
-finally I said screw it..... "I need a second person." My contraption had my friend placed by the DPFE?? the ufo thing behind the Intake I had to hold the 13mm shorty w 1 9" ext by the MAxifuse by the (Black Harness of Pain) "extremely hidden" top alt bolt tight while my friend torqued the rest of the line wich was --> - swivel -9" ext - socket wrench. WOAH. PITA. There is absolutely NO room between engine & firewall to work, with that black harness of pain back there too!! I just couldn't do it how-to style with the socket stack. sorry Ray, had to punk out there. But I got it done. with a quick salty service inquiry at Ford today for a "How much?" to the tune of a savings of roughly $430 bones. Wow, rapeage.
BTW I got a reman Motorcraft 130amp Part # f6rz-10346-bbrm1 $171.41 and a new shiny pulley for 21.06
 
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