Alternator Caught on Fire

[Garfy]

As mentioned earlier, disconnect the wiring going to the alternator, especially the main output cable (the large gauge one). Then reconnect your negative cable to the battery and if it doesn't have that heavy spark like before, your alternator is toast. Out of curiosity, you did replace the alternator with an American made one, not a cheap Chinese one right? I know U.S. alternators are expensive as heck compared to the cheaper Chinese ones from Amazon, etc. but that could be the source of your problem. No Chinese parts in any of my cars; I learned that from my job in seeing too many part failures from O'reilly MasterPro branded stuff (which is all Chinese made).

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[tdstuart]

As mentioned earlier, disconnect the wiring going to the alternator, especially the main output cable (the large gauge one). Then reconnect your negative cable to the battery and if it doesn't have that heavy spark like before, your alternator is toast. Out of curiosity, you did replace the alternator with an American made one, not a cheap Chinese one right? I know U.S. alternators are expensive as heck compared to the cheaper Chinese ones from Amazon, etc. but that could be the source of your problem. No Chinese parts in any of my cars; I learned that from my job in seeing too many part failures from O'reilly MasterPro branded stuff (which is all Chinese made).

Alternator was an ultima alternator from O'reilly.
Pretty sure it was this one: https://www.oreillyauto.com/detail/...129827/automotive-car-2015-ford-mustang?pos=7

 

[Ecto1]

Current measurements are tricky. You can do them with a digital meter but you can damage the meter if the current exceeds the rating of the meter. Current must flow through the meter in order to measure the current. Most digital meters have both a fused connection and an unfused connection. The fused is usually limited to 1A and the unfused is only rated to 10A. This means that if you use the unfused connection and the meter receives over 10A it can kill the meter. You can insert a 10A fuse in the circuit when using the unfused connection. This way if the current exceeds 10A it should blow the fuse. Given your situation I suspect that you are drawing more than 10A. If things are getting hot and burning you're probably drawing MUCH more than 10A.

If this is the case find an analog Ammeter. I have a 50A and a 10A Ammeter I bought on eBay for a few bucks when I was searching for a drain on my battery when the car was turned off. The analog meters shouldn't be damaged from over current. At least a reasonable amount. When you connect the battery cable with the Ammeter in the circuit you will get a surge current that will peg the meter. This shouldn't damage the meter. I started with the 50A meter hoping that the drain wasn't over 50A.Turns out it wasn't. Once I knew I was looking for a problem under 10A I used my digital meter with a 10A fuse to protect it.

One other thing to check is the chassis connection to the battery negative cable. If this connection is loose or corroded it can cause lots of problems with your electrical system. If the negative battery cable is hot at the battery it MIGHT be a poor connection with the chassis. Definitely make sure this connection is solid before searching elsewhere.

Also pull the battery and have it tested at one of the local auto parts stores. They'll check it for free. If they use a hand held tester I wouldn't trust the results. I've had a few bad batteries that showed up as OK on these simple testers. See if you can find a store with a full sized machine for testing the battery. The local Walmart auto department has the only one in my area.

 

[DougS550]

As mentioned earlier, disconnect the wiring going to the alternator, especially the main output cable (the large gauge one). Then reconnect your negative cable to the battery and if it doesn't have that heavy spark like before, your alternator is toast. Out of curiosity, you did replace the alternator with an American made one, not a cheap Chinese one right? I know U.S. alternators are expensive as heck compared to the cheaper Chinese ones from Amazon, etc. but that could be the source of your problem. No Chinese parts in any of my cars; I learned that from my job in seeing too many part failures from O'reilly MasterPro branded stuff (which is all Chinese made).

If your are going with another alternator. For my mustang GT, I would check if a PP1 alternator would fit for it has a larger amp rating. As far as the mustang NAPA or OEM

 

[Garfy]

Current measurements are tricky. You can do them with a digital meter but you can damage the meter if the current exceeds the rating of the meter. Current must flow through the meter in order to measure the current. Most digital meters have both a fused connection and an unfused connection. The fused is usually limited to 1A and the unfused is only rated to 10A. This means that if you use the unfused connection and the meter receives over 10A it can kill the meter. You can insert a 10A fuse in the circuit when using the unfused connection. This way if the current exceeds 10A it should blow the fuse. Given your situation I suspect that you are drawing more than 10A. If things are getting hot and burning you're probably drawing MUCH more than 10A.

If this is the case find an analog Ammeter. I have a 50A and a 10A Ammeter I bought on eBay for a few bucks when I was searching for a drain on my battery when the car was turned off. The analog meters shouldn't be damaged from over current. At least a reasonable amount. When you connect the battery cable with the Ammeter in the circuit you will get a surge current that will peg the meter. This shouldn't damage the meter. I started with the 50A meter hoping that the drain wasn't over 50A.Turns out it wasn't. Once I knew I was looking for a problem under 10A I used my digital meter with a 10A fuse to protect it.

One other thing to check is the chassis connection to the battery negative cable. If this connection is loose or corroded it can cause lots of problems with your electrical system. If the negative battery cable is hot at the battery it MIGHT be a poor connection with the chassis. Definitely make sure this connection is solid before searching elsewhere.

Also pull the battery and have it tested at one of the local auto parts stores. They'll check it for free. If they use a hand held tester I wouldn't trust the results. I've had a few bad batteries that showed up as OK on these simple testers. See if you can find a store with a full sized machine for testing the battery. The local Walmart auto department has the only one in my area.

Yes, measuring current directly by putting an ammeter inline with the cable requires that the ammeter be capable of handling the maximum current in a particular circuit. It's also a PITA because you have to disconnect the circuit and place the ammeter in series with the circuit. I avoid this by using a current probe which has both a low current and high current position and you use it either with a DVOM or graphing MM. They're also good for tracking current draw as you merely clamp it around the wire you're trying to measure the current on.

 

[K4fxd]

Yes, measuring current directly by putting an ammeter inline with the cable requires that the ammeter be capable of handling the maximum current in a particular circuit.

I use clamp on meters. The days of having to wire in an amp meter are long gone.

 

[Garfy]

I use clamp on meters. The days of having to wire in an amp meter are long gone.

Yeah, haven't done that in many decades, hence the current probe.

 

[Basspro302]

Its the alternator, go oem. I have had many of aftermarket reman alternators go bad. One caught fire, just last week one shorted causing the same thing. All these aftermarket parts are pure garbage now. Anything “reman” or well any parts from any of the parts stores stay away. Just buy oem and be done with it.

 

[tdstuart]

Its the alternator, go oem. I have had many of aftermarket reman alternators go bad. One caught fire, just last week one shorted causing the same thing. All these aftermarket parts are pure garbage now. Anything “reman” or well any parts from any of the parts stores stay away. Just buy oem and be done with it.

It’s my guess they don’t like the 8000rpm haha. I wonder what everyone else is using that is revving high. I did accidentally rev this one to 9000…

Probably will keep a fire extinguisher in the car now

I’ll update by the end of the weekend. I’m debating just throwing in another reman one because it’s free but also I have no fire insurance on the car so a fire would be pretty bad.

 

[DougS550]

It’s my guess they don’t like the 8000rpm haha. I wonder what everyone else is using that is revving high. I did accidentally rev this one to 9000…

Probably will keep a fire extinguisher in the car now

I’ll update by the end of the weekend. I’m debating just throwing in another reman one because it’s free but also I have no fire insurance on the car so a fire would be pretty bad.

I agree, Only OEM Alternator. Using a multi meter for checking current is for checking llow amerage electrical circuits because they are sensitive and current below 10 amps I only use "High" quality circuitry clamp on Amp and voltage meter which cost over $150 for them to be accurate and make sure they are used correctly.

 

[Cobra Jet]

Good advice from all…

However prior to this event, you have mentioned you already had to replace the battery and you have already replaced the alternator…. If you have already replaced both - and all manufacturing defects aside that fluid after a “new” or “manufactured part - the issue could be as simple as a voltage regulator issue OR you have a short somewhere.

Here’s some advice for you and others RE: “alternator replacement”:

Most alternators don’t have to be “replaced” when there’s a possible charging issue. Usually the only time an alt would definitely need to be replaced is if the thing is squealing, howling, or seized and that would be due to a high mileage internal alt bearing failure.

The internal windings (field coil) - again usually they don’t fail, but yes there is the possibility.

Now the kicker…
If you were getting a warning light on the dash and you were having charging issues, yes could be the alternator not functioning properly (charging higher than normal or not charging). Usually and in MANY instances this is due to the voltage regulator failing, NOT necessarily an “alternator” failure as in needing to replace the alternator. Most vehicles from about 1987 forward have what is called an internal regulator that is just inserted into the back side of the alternator and secured usually by 2 or 3 Torx security screws depending on alt type. Usually when these regulators start to fail, you will get charging issues and dash warning lights. The voltage regulator is what regulates the charging of the system.

The internal voltage regulators have (2) brushes with springs on them that rides the rotor, which contains the field coil (windings). The springs put tension on the brushes keeping them on the rotor. The regulator monitors the output voltage of the alternator and adjusts the current going through the field coil, which goes out to the electrical system.

If you’re familiar with electric slot cars, then you’ll recall that they too have brushes within the motor. These brushes in a slot car AND in a voltage regulator wear down over time. When they wear down to the “end”, the springs are fully extended and there’s either hardly anything left of the brush or it’s no longer making proper contact on the rotor. At this stage of wear, the function of the voltage regulator is affected, which directly affects the alternator charging - either over charging, not charging, random electrical problems, and throwing dash warning lights.

This is a totally random alternator image pulled offline to show the placement of a modern voltage regulator (circled). You need a security Torx bit to remove it. Voltage regulators are available at many parts stores (brick and mortar or online places like Rock Auto)Super easy to replace…

I believe your initial problem with the stock alt (before you bought a replacement) was a failing voltage regulator which costs far less than a complete alt replacement. This is where many (dishonest) Servicing Dealers and private garages rape people by telling them “you need a new alternator”, because they know the voltage regulator costs far less - but they can “ka-ching” the customer with a much larger bill for a complete alt replacement.

On an S550, as others suggested, also check the BMS because that too plays a role in charging aspects on the newer vehicles.

I would also start checking around in the engine bay and under the car for any wiring that has been chewed through by rodents, which can cause a short…

Be aware that just because you bought a “name brand” part off of Amazon that there are a shit ton of counterfeit goods being sold on Amazon… So despite the name, the packaging, and the quality of the supposed “name brand” part in the package - it could be an offshore fake…. If you just installed those Amazon bulbs and the problem happened - pull those bulbs and really look them over….

 

[tdstuart]

I would also start checking around in the engine bay and under the car for any wiring that has been chewed through by rodents, which can cause a short…

Be aware that just because you bought a “name brand” part off of Amazon that there are a shit ton of counterfeit goods being sold on Amazon… So despite the name, the packaging, and the quality of the supposed “name brand” part in the package - it could be an offshore fake…. If you just installed those Amazon bulbs and the problem happened - pull those bulbs and really look them over….

Good info. Luckily I am in Phoenix Arizona and we don’t have rodent issues that I know of.

I’ll pull the bulbs and see if I notice anything weird just incase for some reason it did cause something.

I’ll try to give an update by the weekend on doing some tests some recommended and seeing if I can point to the alternator or something else for atleast the high current draw I think I am seeing

 

[Basspro302]

Good advice from all…

However prior to this event, you have mentioned you already had to replace the battery and you have already replaced the alternator…. If you have already replaced both - and all manufacturing defects aside that fluid after a “new” or “manufactured part - the issue could be as simple as a voltage regulator issue OR you have a short somewhere.

Here’s some advice for you and others RE: “alternator replacement”:

Most alternators don’t have to be “replaced” when there’s a possible charging issue. Usually the only time an alt would definitely need to be replaced is if the thing is squealing, howling, or seized and that would be due to a high mileage internal alt bearing failure.

The internal windings (field coil) - again usually they don’t fail, but yes there is the possibility.

Now the kicker…
If you were getting a warning light on the dash and you were having charging issues, yes could be the alternator not functioning properly (charging higher than normal or not charging). Usually and in MANY instances this is due to the voltage regulator failing, NOT necessarily an “alternator” failure as in needing to replace the alternator. Most vehicles from about 1987 forward have what is called an internal regulator that is just inserted into the back side of the alternator and secured usually by 2 or 3 Torx security screws depending on alt type. Usually when these regulators start to fail, you will get charging issues and dash warning lights. The voltage regulator is what regulates the charging of the system.

The internal voltage regulators have (2) brushes with springs on them that rides the rotor, which contains the field coil (windings). The springs put tension on the brushes keeping them on the rotor. The regulator monitors the output voltage of the alternator and adjusts the current going through the field coil, which goes out to the electrical system.

If you’re familiar with electric slot cars, then you’ll recall that they too have brushes within the motor. These brushes in a slot car AND in a voltage regulator wear down over time. When they wear down to the “end”, the springs are fully extended and there’s either hardly anything left of the brush or it’s no longer making proper contact on the rotor. At this stage of wear, the function of the voltage regulator is affected, which directly affects the alternator charging - either over charging, not charging, random electrical problems, and throwing dash warning lights.

This is a totally random alternator image pulled offline to show the placement of a modern voltage regulator (circled). You need a security Torx bit to remove it. Voltage regulators are available at many parts stores (brick and mortar or online places like Rock Auto)Super easy to replace…

I believe your initial problem with the stock alt (before you bought a replacement) was a failing voltage regulator which costs far less than a complete alt replacement. This is where many (dishonest) Servicing Dealers and private garages rape people by telling them “you need a new alternator”, because they know the voltage regulator costs far less - but they can “ka-ching” the customer with a much larger bill for a complete alt replacement.

On an S550, as others suggested, also check the BMS because that too plays a role in charging aspects on the newer vehicles.

I would also start checking around in the engine bay and under the car for any wiring that has been chewed through by rodents, which can cause a short…

Be aware that just because you bought a “name brand” part off of Amazon that there are a shit ton of counterfeit goods being sold on Amazon… So despite the name, the packaging, and the quality of the supposed “name brand” part in the package - it could be an offshore fake…. If you just installed those Amazon bulbs and the problem happened - pull those bulbs and really look them over….

We aren’t dishonest or raping people for not replacing a voltage regulator. The part is not available from ford only the complete alternator. Im looking right now and cant find it. Sad fact is that was long ago and if you can find one on the internet it’s probably a knock off and won’t work. Its not the mechanics its the big corporations squeezing every ounce of profit they can while reducing quality.

 

[K4fxd]

I believe the voltage regulator is part of the PCM on the S550 mustang and not on the alt.

 

[Skye]

From the readings I have, the regulator is integrated into the alternator.

"414-00 Charging System - General Information Description and Operation"

"The PCM controls the voltage regulation setpoint and communicates this information to the generator internal voltage regulator over a generator communication (GENCOM) communication circuit. "

"The PCM controlled Smart Charge charging system determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. This system uses 2 communication lines between the PCM and the generator/voltage regulator: A generator communication (GENCOM) line communicates the desired setpoint from the PCM to the voltage regulator, and a generator monitor (GENMON) line communicates the generator load and error conditions to the PCM ."

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