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Old 03-14-2015, 10:26 AM   #1
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Alternator voltage

When I start my 98 2.5 the voltage is 14.4v and slowly drops to around 14.1v Problem is the Becker radio has voltage protection and only works below 14.15v and so cuts out continously. So i suspect the alternators voltage regulator need replacing.

Has anybody else had this?
Does this sound about right?
Can one buy the voltage regulator seperatorly? I think its a VW or Audi part too.
Can the voltage regulator be replaced without having to remove the alternator?

Thanks,

James
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Old 03-14-2015, 10:53 AM   #2
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Originally Posted by James_Hatton View Post
When I start my 98 2.5 the voltage is 14.4v and slowly drops to around 14.1v Problem is the Becker radio has voltage protection and only works below 14.15v and so cuts out continously. So i suspect the alternators voltage regulator need replacing.

Has anybody else had this?
Does this sound about right?
Can one buy the voltage regulator seperatorly? I think its a VW or Audi part too.
Can the voltage regulator be replaced without having to remove the alternator?

Thanks,

James
Couple of possible's here. Yes, the voltage regulator can be problematic, but it is also an over the counter part that is used on VW, Mercedes, and even some Ford models, so it should not be hard to find.

Porsches have also suffered from corrosion build up in the large battery cables, which leads to increased resistance and voltage drops across the cables themselves.

Do a Google search for voltage drop test methods, it only requires a simple electrical multimeter and some time to evaluate your cables to see if the car candidates for replacement.
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Old 03-14-2015, 11:51 AM   #3
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Sounds like the voltage regulator. Voltage should be constant at 13.8 V.
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Old 03-14-2015, 12:03 PM   #4
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Originally Posted by Smallblock454 View Post
Sounds like the voltage regulator. Voltage should be constant at 13.8 V.
Specs on the alternator with the engine running should be 13.5-14.5 V.
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Old 03-14-2015, 12:24 PM   #5
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If the engine is warm, running and is on idle it should stay at 13.8 V in neutral. Even if you turn on parking lights it should regulate back to 13.8 V. If it is 14.4 V there could be a regulator problem that has to be checked.
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Old 03-14-2015, 02:54 PM   #6
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If the engine is warm, running and is on idle it should stay at 13.8 V in neutral. Even if you turn on parking lights it should regulate back to 13.8 V. If it is 14.4 V there could be a regulator problem that has to be checked.
See my above comment on the specifications for voltage output, it is from the factory service manual for the car.
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Old 03-15-2015, 03:16 AM   #7
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Maybe you should connect a voltmeter to your battery instead of reading manuals?
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Old 03-15-2015, 07:00 AM   #8
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Maybe you should connect a voltmeter to your battery instead of reading manuals?
Besides reading the manuals, I also fix them for a living. At 14.1V, that alternator is well within specifications. I still think he should be testing for voltage drop across the cables as that would lower the applied voltage at the radio.
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Old 03-15-2015, 07:59 AM   #9
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Besides reading the manuals, I also fix them for a living. At 14.1V, that alternator is well within specifications. I still think he should be testing for voltage drop across the cables as that would lower the applied voltage at the radio.
He has a high voltage problem, not low. You are so worried about being right that you're not even addressing the correct issue.

Why people think you know something is beyond me. You've never posted a single thing from your own brain. You just regurgitate others work, sometimes inaccurately.
Seriously. Step down from your self-made pedestal. You look ridiculous.
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Old 03-15-2015, 08:38 AM   #10
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He has a high voltage problem, not low. You are so worried about being right that you're not even addressing the correct issue.

Why people think you know something is beyond me. You've never posted a single thing from your own brain. You just regurgitate others work, sometimes inaccurately.
Seriously. Step down from your self-made pedestal. You look ridiculous.
Well, we see Becker equipped cars regularly that are running 14.2 to 14.4V at the alternator, and the radios do not cut out. So unless he has checked voltage at the radio itself, I would still be looking at voltage drop across the cables as the Becker's also are known to drop out at low voltages as well. Checking voltage drop cost nothing, replacing an alternator or voltage regulator that there is nothing wrong with is a waste of money and time.

Now who looks ridiculous?
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Old 03-15-2015, 08:40 AM   #11
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You still do, swinging at air

BTW, I never told him to replace anything, only pointed out the fact that you were not even addressing the issue. Now, you have twisted and molded your own response in order to contort it into a position that may or may not have a grain of validity.

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Old 03-15-2015, 08:58 AM   #12
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You still do, swinging at air

BTW, I never told him to replace anything, only pointed out the fact that you were not even addressing the issue. Now, you have twisted and molded your own response in order to contort it into a position that may or may not have a grain of validity.
Actually, it is the other way around, your employer contacted me. I think I still have his PM if you would like it...........
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Old 03-15-2015, 09:16 AM   #13
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Yeah, right. You've got some nerve trying to mess with a mans job.

Not cold enough, yet
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Old 03-15-2015, 09:50 AM   #14
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Yeah, right. You've got some nerve trying to mess with a mans job.

Not cold enough, yet
I never "messed" with your job in anyway. The gentleman from your firm that called you out on this site for making what they felt were both incorrect, and from their perspective, inappropriate comment's about your employer's manufacturing technologies and products (which promptly resulted in you quickly deleting many of your posts as well as changing you online public information to make yourself harder to trace) happens to be someone that personally knows me and has done more than a little business with me over the last couple of decades; so of course he contacted me.

But that was not your problem; your problem was that you shot off your mouth, made multiple grossly incorrect statements, and your employer justifiably called you out for it. So nothing that I did or said brought this on, you did it all by yourself.
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Old 03-15-2015, 12:39 PM   #15
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What voltage does your 986 2.5 run at?

Wow, thanks guys, you've throw handbags and everything into the ring. I'm flattered. But now chill!

My problem is exactly the same described by the guy in this thread:

http://986forum.com/forums/general-discussions/31114-boxster-986-1998-radio-cutting-out.html

I am still convinced its an over voltage issue. Exactly as this guy describes, it works fine with the engine off at 12.8v but with the engine on at 14.4v it does not. Then also as he describes it starts working once its warm. We all know that as alternators get warm they become slightly less efficient, and hence the radio begins to work again. Also if the radio is cut out and I add a load to the electrical circuit, like turn the lights on or the window demister then the radio starts working again.

So now we're established its an over voltage issue let me rather ask:

What voltage does your 986 2.5 run at?
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Old 03-15-2015, 12:52 PM   #16
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Back to the issue?
Smallblock is very modestly concealing his expertise .he has some impressive connections(pun intended) in the automotive engineering business in Germany. He said:
"Sounds like the voltage regulator. Voltage should be constant at 13.8 V."
So let's try to understand first and debate only when the facts are understood ?
13,8v -gotta love that precision :-). Is that 13.8v +/- 0.5v for example or exactly 13.8v ? I ask because that would be an extremely useful Volts value to use in diagnostics.It is also very easy to test accurately.
If we get JFP's reading range(per the Factory Manual) of 13.5 to 14.5v what does this indicate -if anything?
For example is 13.5v a problem that the Becker radio coincidentally indicates ? or is it just a 'normal' variation? High resistance/corroded cables seem to be a theoretical possibility. I have seen reports of this issue at the battery end of the +ve main battery cable. Just strip off some insulation to observe/check.
Similarly , what does 14.5 (instead of 13.8v) tell us ? Just a Voltage Regulator that is beginning to fail?
I guess you would also need to know the un-regulated Alternator output voltage also -if it was reading low ?
Just trying to understand/clarify the issue.
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Old 03-15-2015, 12:59 PM   #17
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James,
To make sure we give you good suggestions, please tell us exactly where you are measuring the voltage.
You said:
"Problem is the Becker radio has voltage protection and only works below 14.15v and so cuts out continuously"
If you get different voltage readings in various locations ,that may be very useful. If there is an abnormally high resistance in the circuits, that would cause all sorts of aberrant problems. The obvious comparison would be voltage from the alternator VR compared to at the battery cables on the battery. Check battery cable to ground/body connection also?
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Old 03-15-2015, 01:39 PM   #18
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I was reading the voltage directly across the battery terminals, with a digital voltmeter.

12.8v without the engine running.
14.4v immediately after starting the engine.

The voltage then gradually drops over a period of about 5 minutes to 14.1v

Adding loads like the lights or rear demister also pulls the voltage down but only very slightly.

I came across this issue on the 996 on the web, but I'm battling to find the page again.

PS Check the voltage on my Touareg to compare and it stayed perfectly on 13.8v under all conditions.

Hey, I've just figured it out, put the Treg alternator in the Boxster, hehe! It's 200A if I can remember correctly.
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Old 03-15-2015, 01:45 PM   #19
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" the voltage on my Touareg to compare and it stayed perfectly on 13.8v under all conditions."
Smallblock was correct. I guess he knows something about this issue that the Factory Manual does not make clear?
Now we need to figure out what voltage to expect where & why.
We had better be nice to Markus(a.k.a. Smallblock) and ask him?
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Old 03-15-2015, 02:32 PM   #20
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@ James_Hatton:

Under the conditions i described above in post #5 the voltage should be stable at around 13.8 volts. There are some factors that can lower the voltage. The voltage should not go above 13.9 volts. 14.4 volts is too much. I think your problem is a dying voltage regulator.

Voltage regulators in Bosch alternators of that time can most often be replaced seperately. If you have a Bosch Service near you, you should ask them to check and perhaps repair the alternator; or send it in. Maybe they can repair it.

In germany Bosch has a lot of Service stations called Bosch Dienst. They are competent and specialized repair shops for all Bosch products.

Else unhappily you have to replace the complete alternator, which in my opnion is often not that useful, because contacts, brushes (don't know if that is the right term) and bearings normally can be changed by a specialized service shop. I'm not a friend of planned obsolescence.

Regards from germany
Markus

PS: i'm nobody, know nobody and know nothing.

Last edited by Smallblock454; 03-16-2015 at 12:13 AM.
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