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Car Forum / Ford / Ford Mustang / August 2005Alternator replacement -- problem
My car died (alternator has been weakening..now crapped out earlier today) & I replaced the alternator. I jump started the car after I replaced the alternator & it fired right up. The voltage level (according to the car gauge) was dead in the center of the "R" in "NORMAL" on the gauge.. normally it's on the "N" or "O". The problem is... the battery symbol (MIL) is illuminated (red). It is not going away at all. I tried disconnecting the battery ground cable for 25 mins to reset the computer, but this didn't work. It holds a good charge, but the light will not go away. I checked all fuses & none are blown. Any thoughts? Car is a 1998 Ford Mustang GT. Thanks!!!!!! -Mike > My car died (alternator has been weakening..now crapped out earlier > today) & I replaced the alternator. I jump started the car after I [quoted text clipped - 13 lines] > > -Mike What is the voltage output of the new alternator? Are you sure it's charging?  SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 7:36 1 user I don't have a multimeter anymore.. can't find mine. It's def. "better" than before though. I'm pretty positive it's charging. -Mike >I don't have a multimeter anymore.. can't find mine. It's def. "better" >than before though. I'm pretty positive it's charging. > >-Mike A inexpensive thing to do would be to run down to the local Radio Shack and pick up a $5-$10 DMM (digital multi meter). It's hard to diagnose anything through a computer with out at least a modicum of information. ...Ron -- 68' Camaro RS 88' Firebird Formula 00' Mustang GT Vert I went to Autozone because my buddy is a manager there & he brought out the battery tester... it's apparently in extremely good condition, EXCEPT at idle with headlights on & A/C going full blast... it's drawing about 4-5 amps (-4 to -5 displayed). I snipped the battery cables & re-connected them to the terminals with new battery terminal connectors... didn't help. I cleaned the battery terminals as well. I also tightened all connections w/ the alternator (which was just 1... the power wire..). Any thoughts? This stinkin' red battery light remains illuminated. -Mike > I went to Autozone because my buddy is a manager there & he brought out > the battery tester... it's apparently in extremely good condition, [quoted text clipped - 8 lines] > > -Mike Apparently, your alternator is not supplying enough current to charge the battery and run the electrical accessories.You really need to measure the output voltage... why didn't your Autozone buddy measure it? SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 23:31 1 user So you're thinking the alternator could be at fault? I'll go to Hammons Auto Parts first thing Monday (where I bought it) and let them test it. Grrr.. what a pain in the a.s =(. -Mike > So you're thinking the alternator could be at fault? I'll go to Hammons > Auto Parts first thing Monday (where I bought it) and let them test it. > Grrr.. what a pain in the a.s =(. > > -Mike An alternator works by creating a rotating magnetic field which cuts across a set of wire windings. As Mr. Faraday and Mr. Maxwell told us, a changing magnetic field intersecting ith a wire creates a current in the wire. Since the field is rotating, the current alternates between positive and negative and thus creats alternating current (AC). Strategically placed diodes forces the current to go in the same direction, thus creating direct current (DC). The rotating field is created as DC current from the battery flows through slip rings to a field winding on a rotor that is spun by the belt pulley. Some time ago I disassembled the alt. on my Torino and installed a "hi-output" kit.. new brushes, different stator winding, and some bigger diodes. If I am at a slow idle (stopped at a stop light whilst still in drive), the alternator output will drop enough that the voltmeter drops below 13 volts. The regulator leaks enough current through the ALT light to turn it on just barely in that case. Goosing the throttle makes it go back to normal. The regulator is trying to put enough field current through the rotor to keep the voltage up at low RPM. When it hits the maximum current, the output voltage drops and the light comes on. The OEM style regulator was only able to vary the field current discretely, it had a relay inside that basically turn the field on and off to maintain the output voltage. An electronic regulator (which I have now) can vary it across the range of adjustment. Guess what, 35 years later, alternators still work the same way, except now the regulator is built into the unit. I would take the unit back and have it tested. I haven't ever had too much luck with generic auto parts stores alternators, they don't really last very long. I would try NAPA. Also, it's possible that they didn't hook it up right.... SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 1 day 9:01 I'll go ahead & pull the alternator out of the car & have it tested. Thanks!! -Mike > I'll go ahead & pull the alternator out of the car & have it tested. > Thanks!! > > -Mike I thought that's what you did at AutoZone?? Signature"Network management is like trying to herd cats." -- Unknown "I wonder how much deeper the ocean would be without sponges?" -- TazAmd - Humor Section Gettingtogather.com Well, he hooked it up to the battery... and tested both, but I want Hammons to specifically test the alternator when it's removed from the car. I figure they could do a more thorough examination, no? I dunno. I might just try to get a refund from them & get an alternator from a more "recognized" establishment.. like local NAPA store. -Mike > Well, he hooked it up to the battery... and tested both, but I want > Hammons to specifically test the alternator when it's removed from the [quoted text clipped - 3 lines] > > -Mike Yabut, you don't have to take it out to test it, infact it's better in the car and you can test at different RPM. Signature"Network management is like trying to herd cats." -- Unknown "I wonder how much deeper the ocean would be without sponges?" -- TazAmd - Humor Section Gettingtogather.com Well in that case I'm just going to simply request a refund & go to a more reputable parts store. Thanks. -Mike > Well in that case I'm just going to simply request a refund & go to a > more reputable parts store. Thanks. > > -Mike But from what you have described, there is nothing wrong with the alternator. Signature"Network management is like trying to herd cats." -- Unknown "I wonder how much deeper the ocean would be without sponges?" -- TazAmd - Humor Section Gettingtogather.com >> Well in that case I'm just going to simply request a refund & go to a >> more reputable parts store. Thanks. [quoted text clipped - 3 lines] > But from what you have described, there is nothing wrong with the > alternator. ??? He said the alt. light was on all the time, and no one has measured the voltage at the output. SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 4 days 7:38 > ??? He said the alt. light was on all the time, and no one has > measured the voltage at the output. Which is why nothing he has said indicates it needs to be replaced. The output needs to be tested first. Signature"Gullible is a misdemeanor - stupid is a felony... clueless gets you committed..." - JG >> ??? He said the alt. light was on all the time, and no one has >> measured the voltage at the output. > > Which is why nothing he has said indicates it needs to be replaced. > The output needs to be tested first. You are mighty right. Mike, you need to get somebody with a VOLTMETER to measure the output voltage of the alternator at slow and fast engine speeds. SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 4 days 22:30 >> I went to Autozone because my buddy is a manager there & he brought out >> the battery tester... it's apparently in extremely good condition, [quoted text clipped - 13 lines] > output > voltage... why didn't your Autozone buddy measure it? Many alternators can't run the AC full blast and the lights at an idle. A lot depends on the design of the charging system. The real question is not what the battery voltage is, but what would a similar car with a good charging system do under the same conditions. A car with an engine that pulls a lot of RPM has the have the alternator "geared" to not exceed its RPM limit. At idle that alternator will turn slower. Like when you install a pulley kit. Al >>> I went to Autozone because my buddy is a manager there & he brought out >>> the battery tester... it's apparently in extremely good condition, [quoted text clipped - 23 lines] > > Al Right... I didn't think to ask if he had a pulley kit on the thing. SignatureDavid M (dmacchiarolo) http://home.triad.rr.com/redsled T/S 53 sled351 Linux 2.4.18-14 has been up 3 days 17:06 >>>> I went to Autozone because my buddy is a manager there & he >>>> brought out the battery tester... it's apparently in extremely [quoted text clipped - 28 lines] > Right... I didn't think to ask if he had a pulley > kit on the thing. Pulleys killed my LX. I was going through a battery every 10-12 months, and the thing was never charging unless it was turning at least 1500 rpm. And that's not mentioning the overheating problems in the summer. Put the stock pulleys back on and everything's great. Joe Calypso Green '93 5.0 LX AOD hatch with a few goodies Black '03 Dakota 5.9 R/T CC Stock pulleys are on. I never had much interest in underdrive pulleys. The battery light stays illuminated ALL the time..not just at idle. I want that light GONE.. don't want to hafta replace the battery every few months. It's drawing power from battery at idle with headlights on & A/C full blast... and that's the only time, but still... it's a pet peeve at least & that's enough to make me replace the alternator w/ a better one. -Mike > Stock pulleys are on. I never had much interest in underdrive pulleys. > [quoted text clipped - 6 lines] > > -Mike Mike, you've got a problem somewhere if that light's lit all the time. Double-check the alt, maybe get another replacement. Check the wiring leading up to the alt also. HTH. > Stock pulleys are on. I never had much interest in underdrive pulleys. > [quoted text clipped - 6 lines] > > -Mike If it does it ALL the time then the alt is out right bad OR you have a different problem. I seem to remember a blown fuse causing that problem. Signature"Network management is like trying to herd cats." -- Unknown "I wonder how much deeper the ocean would be without sponges?" -- TazAmd - Humor Section Gettingtogather.com > Pulleys killed my LX. I was going through a battery every 10-12 > months, and the thing was never charging unless it was turning at [quoted text clipped - 6 lines] > Calypso Green '93 5.0 LX AOD hatch with a few goodies > Black '03 Dakota 5.9 R/T CC Joe Did that restore the air bag light situation or did you replace the module??? Was curious about the outcome from a few weeks ago. Got an update??? -- Mike 93 Cobra > I went to Autozone because my buddy is a manager there & he brought out > the battery tester... it's apparently in extremely good condition, > EXCEPT at idle with headlights on & A/C going full blast... There you go, life with a Fox Mustang. I have the new alternator (3G) and at idle with the lights and Max AC it does the same thing. Signature"Network management is like trying to herd cats." -- Unknown "I wonder how much deeper the ocean would be without sponges?" -- TazAmd - Humor Section Gettingtogather.com >> I went to Autozone because my buddy is a manager there & he brought out >> the battery tester... it's apparently in extremely good condition, >> EXCEPT at idle with headlights on & A/C going full blast... > > There you go, life with a Fox Mustang. I have the new alternator (3G) > and at idle with the lights and Max AC it does the same thing. I'd still check the pulleys. if the alternator came with a pulley (you did not have to pull yours off and put it on the shaft) as a direct swap you may have a problem. The alternator in my T-bird was replaced. and i got the same symptons. low voltage/amps at idle and that damn bell ringing and the battery picture flashing all the time. It turns out that the alternator pulleys come in slightly different sizes depending on auto vs manual and different sizes depending on the accesory load. as my t-bird was an LX with heated rear glass the origiannl pullery was quite small (taller ratio) the NAPA replacement with a pulley installed was about 1/2" bigger. when i tried a smaller pulley on the alternaor only the problem went away. The Idiot light transistor in the VReg is bad. Had the same problem in a "rebuilt" from autozone... the Alt works fine otherwise so I said to he!! with it. You can get a new alt or a new VR or a used VR. easy to replace > My car died (alternator has been weakening..now crapped out earlier > today) & I replaced the alternator. I jump started the car after I [quoted text clipped - 13 lines] > > -Mike |
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