alternator problems
04-20-2004, 04:25 PM
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alternator problems
hey guys & gals last year i removed my alternator because the voltage gauge in the car was showing 12 to 13 volts at normal rpm 2-3 k. well my car is a 944 turbo s and the alternator is a real pita to remove but i got it out took it to a repair shop. they bench tested it and said this alternator is fine. so i put it back in and it still shows the same thing. i used a volt meter at the battery and it shows the same as the gauge 12 to 13 volts. i thought they were suppose to put 13.5 to 14 back to the battery. this also
get worse when i put the air conditioning on the volt meter drops more. also the hotter it is outside the lower the volt meter reading. could the regulator be going and when it is hot it doesn't work well but when cold no problem. as upon starting in the morning the volt meter is 13.5 to 14. do i have to take it out again? or is there grounds i should check/clean that may cause this? any other ideas besides the taking the alter. out again.
greg
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get worse when i put the air conditioning on the volt meter drops more. also the hotter it is outside the lower the volt meter reading. could the regulator be going and when it is hot it doesn't work well but when cold no problem. as upon starting in the morning the volt meter is 13.5 to 14. do i have to take it out again? or is there grounds i should check/clean that may cause this? any other ideas besides the taking the alter. out again.
greg
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04-20-2004, 05:32 PM
#2
Nordschleife Master
You should have put in a higher voltage, voltage regulator when you had the alternator out. That would help get the battery up to full charge faster and remove the recharging load off the system. It only takes a minute to change the regulator out, but on a turbo you need to remove the alternator to get at things and that takes some work as you found out.
As far as voltage levels dropping with heat, that is normal. The alternator diodes lose efficiency when they get hot. The voltage regulator also has a circuit to drop voltage a bit under hot conditions. With everything in good shape, but very hot outside (say up towards 100*F) you may see between 0.5 to 0.75 volts drop. To reduce the voltage drop make sure the heat shield is in place at the back of the alternator and the cooling hose from the front air scoop is attached to the shield.
As far as voltage drop under higher current loads you have two issues. One is that the alternator can't make 14.4 volts once the load gets up towards somewhere around 45 amps. And the maximum volts the alt can make keeps droping the higher the load. Nothing you can do about this other than getting a larger alternator which is sort of impractical due to mounting issues and cost if you are concerned about money. There is also the voltage loss due to resistance in the wiring and the higher the load the more voltage you will lose. Here is where cleaning up terminal attachments, replacing the positive and negative battery cables with new and larger, and adding supplemental grounds and positives can reduce the resistance voltage losses.
You can also go and rewire the components that are important to you and are severely effected by low voltage. The big one is headlights. You lose only 15% of the voltage actually delivered to the headlight bulbs and you just lost 50% of light output. In other words if you can increase the voltage to the lights just 15% you will increase your headlight performance by 100%.
As far as voltage levels dropping with heat, that is normal. The alternator diodes lose efficiency when they get hot. The voltage regulator also has a circuit to drop voltage a bit under hot conditions. With everything in good shape, but very hot outside (say up towards 100*F) you may see between 0.5 to 0.75 volts drop. To reduce the voltage drop make sure the heat shield is in place at the back of the alternator and the cooling hose from the front air scoop is attached to the shield.
As far as voltage drop under higher current loads you have two issues. One is that the alternator can't make 14.4 volts once the load gets up towards somewhere around 45 amps. And the maximum volts the alt can make keeps droping the higher the load. Nothing you can do about this other than getting a larger alternator which is sort of impractical due to mounting issues and cost if you are concerned about money. There is also the voltage loss due to resistance in the wiring and the higher the load the more voltage you will lose. Here is where cleaning up terminal attachments, replacing the positive and negative battery cables with new and larger, and adding supplemental grounds and positives can reduce the resistance voltage losses.
You can also go and rewire the components that are important to you and are severely effected by low voltage. The big one is headlights. You lose only 15% of the voltage actually delivered to the headlight bulbs and you just lost 50% of light output. In other words if you can increase the voltage to the lights just 15% you will increase your headlight performance by 100%.
04-20-2004, 08:12 PM
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iceshark
thanks for the response do you think it is worth the effort to take it out again and have them replace the regu. brushes, bearings, and then see how it performs or just go for the higher volt reg and be done with it. will the higher volt reg do anything else ie. over charge the battery?
thanks again
greg
thanks for the response do you think it is worth the effort to take it out again and have them replace the regu. brushes, bearings, and then see how it performs or just go for the higher volt reg and be done with it. will the higher volt reg do anything else ie. over charge the battery?
thanks again
greg
04-20-2004, 09:21 PM
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83na944
i have a problem. the repair shop i took it to bench tested it and said fine.
i should have had them replace the reg, bearings, brushes, even if they said they were fine. as i think as the temp goes up this summer the volt reg performance goes down. running the air cond pulls the volt meter to around 12 volts if i run the headlights also i run the risk of draining the battery while the car is going down the highway. it must have to do with the reg getting hot while the car is running and then it starts to act up.
i talked to a general mechanic (not porsche specific) and he said that happens when the reg starts getting weak. i really wanted to know if i was missing something else to check before i rip the damn alter. out again.
greg
i have a problem. the repair shop i took it to bench tested it and said fine.
i should have had them replace the reg, bearings, brushes, even if they said they were fine. as i think as the temp goes up this summer the volt reg performance goes down. running the air cond pulls the volt meter to around 12 volts if i run the headlights also i run the risk of draining the battery while the car is going down the highway. it must have to do with the reg getting hot while the car is running and then it starts to act up.
i talked to a general mechanic (not porsche specific) and he said that happens when the reg starts getting weak. i really wanted to know if i was missing something else to check before i rip the damn alter. out again.
greg
04-20-2004, 10:08 PM
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[QUOTE]Originally posted by IceShark
[B]You should have put in a higher voltage, voltage regulator when you had the alternator out. That would help get the battery up to full charge faster and remove the recharging load off the system.
I have to disagree on this one. The set point of the regulator has nothing to do with how fast the battery gets recharged. The higher set point only raises the full-charge state of the battery and has no effect on charging until that point is reached.
How fast the battery gets recharged is strictly a function of rpm, alternator efficiency, and real-time electrical load(s) on the system.
Doug
[B]You should have put in a higher voltage, voltage regulator when you had the alternator out. That would help get the battery up to full charge faster and remove the recharging load off the system.
I have to disagree on this one. The set point of the regulator has nothing to do with how fast the battery gets recharged. The higher set point only raises the full-charge state of the battery and has no effect on charging until that point is reached.
How fast the battery gets recharged is strictly a function of rpm, alternator efficiency, and real-time electrical load(s) on the system.
Doug
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04-20-2004, 10:20 PM
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[QUOTE]Originally posted by greg rx2
[B]83na944
i have a problem. the repair shop i took it to bench tested it and said fine.
Kindly read one of my previous postings below, then tell me what you think of a bench test:
Due to the vast amount of misinformation I see posted regarding alternators I’m going to offer a semi long-winded diatribe on the subject. If the inner workings of alternators don’t interest you, skip the rest of this post. My license to speak with authority on this subject comes from 27+ years as the hands-on owner of a starter-alternator rebuilding shop.
When you have a low charge rate and you replace the regulator, it may seem to work better temporarily (provided that was the actual problem) but you’ve only fixed part of the problem. Included with that regulator you just replaced is a set of brushes. These brushes ride on two rings on the rotor (the spinning part inside). Now stay with me….the amount of output is controlled by how much current goes through a brush into one ring, through the rotor coil and back out the other ring, through the other brush and to ground. The more current, the more magnetism, the more output. Problem is, in most alternators full output only requires 4A of current though the rotor. When you replaced the regulator, you probably never realized that a lot of the carbon (built up on the rings) from the old worn brushes would lead you right back to the intermittent charging problem you were trying to solve. You may pass an amp or two through dirty rings, but you’ll never get what you need in high-demand situations. These rings need to be polished out with 600 paper until they look like new so full current can pass through when required. Any used alternator that has been sitting is GUARANTEED to have this problem. The rings are copper, and copper oxidizes. Go look at the pipes in your basement if you disagree.
If you keep a fresh, spare alternator, put it in a Ziploc bag.
The next problem. This one, especially on higher mileage Bosch (Porsche) units, is really common. You may find the aforementioned rings are deeply grooved or are no longer concentric. Slight grooves that ARE concentric are OK, but anything worse than that will require professional help. Well out-of-round rings cause the brushes to hop up and down with every rotation (making RF noise, too), and eventually the brush wires break off.
I seldom see a bad Bosch regulator, maybe one out of fifteen or twenty units. The adjustable regulator is fine if you want to play, but you won’t be any better off with it if you don’t heed my advice above and correct your problems. I will say that it is easier for the home mechanic to simply change the regulator than to change the brushes, especially without good soldering skill or equipment.
To just remove a regulator and bolt another one is simply a half-assed solution without checking and correcting the above stuff.
Doug
[B]83na944
i have a problem. the repair shop i took it to bench tested it and said fine.
Kindly read one of my previous postings below, then tell me what you think of a bench test:
Due to the vast amount of misinformation I see posted regarding alternators I’m going to offer a semi long-winded diatribe on the subject. If the inner workings of alternators don’t interest you, skip the rest of this post. My license to speak with authority on this subject comes from 27+ years as the hands-on owner of a starter-alternator rebuilding shop.
When you have a low charge rate and you replace the regulator, it may seem to work better temporarily (provided that was the actual problem) but you’ve only fixed part of the problem. Included with that regulator you just replaced is a set of brushes. These brushes ride on two rings on the rotor (the spinning part inside). Now stay with me….the amount of output is controlled by how much current goes through a brush into one ring, through the rotor coil and back out the other ring, through the other brush and to ground. The more current, the more magnetism, the more output. Problem is, in most alternators full output only requires 4A of current though the rotor. When you replaced the regulator, you probably never realized that a lot of the carbon (built up on the rings) from the old worn brushes would lead you right back to the intermittent charging problem you were trying to solve. You may pass an amp or two through dirty rings, but you’ll never get what you need in high-demand situations. These rings need to be polished out with 600 paper until they look like new so full current can pass through when required. Any used alternator that has been sitting is GUARANTEED to have this problem. The rings are copper, and copper oxidizes. Go look at the pipes in your basement if you disagree.
If you keep a fresh, spare alternator, put it in a Ziploc bag.
The next problem. This one, especially on higher mileage Bosch (Porsche) units, is really common. You may find the aforementioned rings are deeply grooved or are no longer concentric. Slight grooves that ARE concentric are OK, but anything worse than that will require professional help. Well out-of-round rings cause the brushes to hop up and down with every rotation (making RF noise, too), and eventually the brush wires break off.
I seldom see a bad Bosch regulator, maybe one out of fifteen or twenty units. The adjustable regulator is fine if you want to play, but you won’t be any better off with it if you don’t heed my advice above and correct your problems. I will say that it is easier for the home mechanic to simply change the regulator than to change the brushes, especially without good soldering skill or equipment.
To just remove a regulator and bolt another one is simply a half-assed solution without checking and correcting the above stuff.
Doug
04-20-2004, 10:42 PM
#10
Nordschleife Master
Well that is not really true Doug. The stock regulator is set at 14.0 or 14.1 volts and that is all that will get out under optimal conditions. If you put in a 14.4v regulator and the alternator still has legs you will put 14.4 v into the battery and push it up to full charge much faster. That 0.4v additional differential really makes a difference. Now if you are drawing 90 amps off the alternator, which regulator you have makes no difference because neither will limit the voltage level as the alternator can't make it there under those loads. Period.
Greg, well you know know the work involved in pulling the alternator so you decide. I'd do it if you have some other work to do in the area. The voltage regulator will come with attached brushes so the other item on your wish would be bearings. They are most likely just fine and don't need to be replaced. A voltage regulator set at 14.4v will not overcharge the battery so nothing to worry about there. Many automakers put in voltage regulators that are set up towards 15 volts and there is no big rush on replacement batteries. Though I wouldn't go that high.
Get my Full Boat headlight package and you can do the whole job (headlight package includes a new voltage regulator) and up your headlight performance by several hundreds percent, some have bumped performance up by 450%. Then you have a good reason to go pull the alternator again. And that is the hardest part of the install job.
The full package includes the Cibie E-Code lenses, (4) 90/100 H4 bulbs (extra pair), wiring harness and supplemental ground, adjustable voltage regulator and attached brushes, instructions, shipping, etc. Total cost is now $369.50. Since you have had the alt out once already your installation should go fairly quick as you know how to do the most difficult part.
Greg, well you know know the work involved in pulling the alternator so you decide. I'd do it if you have some other work to do in the area. The voltage regulator will come with attached brushes so the other item on your wish would be bearings. They are most likely just fine and don't need to be replaced. A voltage regulator set at 14.4v will not overcharge the battery so nothing to worry about there. Many automakers put in voltage regulators that are set up towards 15 volts and there is no big rush on replacement batteries. Though I wouldn't go that high.
Get my Full Boat headlight package and you can do the whole job (headlight package includes a new voltage regulator) and up your headlight performance by several hundreds percent, some have bumped performance up by 450%. Then you have a good reason to go pull the alternator again. And that is the hardest part of the install job.
The full package includes the Cibie E-Code lenses, (4) 90/100 H4 bulbs (extra pair), wiring harness and supplemental ground, adjustable voltage regulator and attached brushes, instructions, shipping, etc. Total cost is now $369.50. Since you have had the alt out once already your installation should go fairly quick as you know how to do the most difficult part.
04-20-2004, 11:28 PM
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Greg,
What I was asking is have you had a battery discharged this way or any other problem relaterd to this? I mean not just the voltmeter telling you that you have a low voltage? Maybe you really don't have a problem. Apparently the alternator shop thinks there is no problem.
Anyway, I'd replace the brushes/voltage regulator if you have it off. The piece is relatively cheap. Even if it doesn't solve the problem, it probably won't hurt. If you have to have the alternator rebuilt, you're only out a little money.
Good Luck,
Steve
What I was asking is have you had a battery discharged this way or any other problem relaterd to this? I mean not just the voltmeter telling you that you have a low voltage? Maybe you really don't have a problem. Apparently the alternator shop thinks there is no problem.
Anyway, I'd replace the brushes/voltage regulator if you have it off. The piece is relatively cheap. Even if it doesn't solve the problem, it probably won't hurt. If you have to have the alternator rebuilt, you're only out a little money.
Good Luck,
Steve
04-21-2004, 08:04 PM
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Greg,
Maybe the solution for your problem is a piece of duct tape over the voltmeter.
Seriously, when it gets to be a problemor when you're worried about it so much that you're willing to pull the alternator, then take it out and replace the voltage regulator. Or take it to the shop and tell them to rebuild it regardless of the test results.
Good luck,
Steve
Maybe the solution for your problem is a piece of duct tape over the voltmeter.
Seriously, when it gets to be a problemor when you're worried about it so much that you're willing to pull the alternator, then take it out and replace the voltage regulator. Or take it to the shop and tell them to rebuild it regardless of the test results.
Good luck,
Steve
04-21-2004, 09:56 PM
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[QUOTE]Originally posted by IceShark
[B]Well that is not really true Doug. The stock regulator is set at 14.0 or 14.1 volts and that is all that will get out under optimal conditions. If you put in a 14.4v regulator and the alternator still has legs you will put 14.4 v into the battery and push it up to full charge much faster. That 0.4v additional differential really makes a difference. Now if you are drawing 90 amps off the alternator, which regulator you have makes no difference because neither will limit the voltage level as the alternator can't make it there under those loads. Period.
Ice;
You won't be putting 14.4 volts into a battery that currently has 12.6 (or anything less than 14.4). The voltage climbs gradually as the battery becomes fuller. The 14.4 volt setting is the limit of the charge and means nothing on the trip to attain that voltage.
At the risk of making a bad analogy, AND if I understand your theory correctly let me try this. Liken the amperage to a football player running for the goal. Under your theory he's running faster than he used to...but (I say) that now the goal post is further away making the trip take the same amount of time as when he ran slower.
Doug
[B]Well that is not really true Doug. The stock regulator is set at 14.0 or 14.1 volts and that is all that will get out under optimal conditions. If you put in a 14.4v regulator and the alternator still has legs you will put 14.4 v into the battery and push it up to full charge much faster. That 0.4v additional differential really makes a difference. Now if you are drawing 90 amps off the alternator, which regulator you have makes no difference because neither will limit the voltage level as the alternator can't make it there under those loads. Period.
Ice;
You won't be putting 14.4 volts into a battery that currently has 12.6 (or anything less than 14.4). The voltage climbs gradually as the battery becomes fuller. The 14.4 volt setting is the limit of the charge and means nothing on the trip to attain that voltage.
At the risk of making a bad analogy, AND if I understand your theory correctly let me try this. Liken the amperage to a football player running for the goal. Under your theory he's running faster than he used to...but (I say) that now the goal post is further away making the trip take the same amount of time as when he ran slower.
Doug
04-22-2004, 10:14 AM
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How difficult is it to take the alternator apart to clean the rings and replace the brushes? I'm feeling masochistic right now and am ready for my next project