Alternator Voltage

[MarkC]

First of all thanks to Ahsai for the post on the wire and inspection mirror in order to access the rear of the alternator.

Same story as many others here, 14v at start up and as the car warms, drops to 13v (with nothing running). Dash volt meter drops to 12v with lights, a/c on, but actually measures 12.7v at jump start post and battery. I replaced the voltage regulator 9 months ago, appeared OK for 3-4 months. During the summer the problem re-occurred. I read many posts on other's problems.

When the engine is warm, the voltage drop from the back of the alternator to the +ve post in the engine bay (jump start post ?) is 0.8 volts, obviously way too high.

Car is a MY 2000 911 C2. There appears to be 2 different harness images posted from the various discussions, so I'm trying to figure out am do I need to replace the Y cable #28 or #21 from the respective images.

Also how difficult is this after the alternator is back out? Hoping not as bad as Equinox 997 post. Is it the same as Ahasi's description in this link? http://www.renntech.org/forums/topic/44682-how-do-i-replace-the-cable-from-the-alternator-to-the-starter/

Thanks

Mark

[Ahsai]

First of all thanks to Ahsai for the post on the wire and inspection mirror in order to access the rear of the alternator.

Same story as many others here, 14v at start up and as the car warms, drops to 13v (with nothing running). Dash volt meter drops to 12v with lights, a/c on, but actually measures 12.7v at jump start post and battery. I replaced the voltage regulator 9 months ago, appeared OK for 3-4 months. During the summer the problem re-occurred. I read many posts on other's problems.

When the engine is warm, the voltage drop from the back of the alternator to the +ve post in the engine bay (jump start post ?) is 0.8 volts, obviously way too high.

Car is a MY 2000 911 C2. There appears to be 2 different harness images posted from the various discussions, so I'm trying to figure out am do I need to replace the Y cable #28 or #21 from the respective images.

Also how difficult is this after the alternator is back out? Hoping not as bad as Equinox 997 post. Is it the same as Ahasi's description in this link? http://www.renntech.org/forums/topic/44682-how-do-i-replace-the-cable-from-the-alternator-to-the-starter/

Thanks

Mark

Hi Mark,

Glad to hear the wire trick works for you. Yours should be #21 in this diagram

http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996-99-05&section=902-05

The other diagram you saw was probably for the Boxsters.

Send your VIN to Sunset Porsche parts and they will send you the right cable. Regarding replacement, I can't say for sure since mine is an '03 but I would imagine the design should be similar. Hopefully someone who knows will chime in.

[MarkC]

Ahsai,

I've removed airbox, alternator, throttle body and intake plenum - so now have access to the starter wiring. Took less than 1 hour, not bad so far.

One of your other posts states the AC compressor must be loosened to remove the wire. Does the jump start post not come apart, so only the #21 wire and spade can be withdrawn? I can see (and almost touch the whole length of the wire) and there appears to be sufficient space for the wire & spade to pass between the compressor and intake. Am I missing something? Might be looking for more guidance if the compressor has to be removed.

Is it possible to fish the wire(s) the other way out, i.e. pulled from the jump post, between compressor and intake? Guess I'll find all this out next weekend, after the parts arrive.

Thanks

Mark

[Ahsai]

Mark, sounds like you are making pretty good progress. Yes, the jump post "head" is too big that I had to remove the ac compressor to create clearance. No, pulling from the jump post side would not work, at least not for me. It will be much clearer once you got the new cable in your hand. I do hope that you find some shortcut though. Keep us posted.

[MarkC]

The connection at the starter was the problem, heavily corroded - see first 2 images below. My car spent 3 years in Boston, and the last 10 in Southern California where it hasn't see rain since. Parts ordered, but not in stock, so I have 5 days to figure out the last 2 challenges...

I've succumbed to the fact the AC Compressor has to come off. I removed the temp sensor and can see a bolt which looks like it's on a bracket directly below what appears to be a HVAC line - see next image. Is this the correct bolt? Just a little concerned on how to get it back in after removal. Anything else I need to know here (other wires/hoses etc to come off)? Any gotcha on that rear bolt?

As far as the power steering reservoir. I presume rotate the red circled (last image) lock at which point whatever is in the reservoir is coming out (unless I suck out what's in there first). Is that correct?

Thanks

Mark

[Ahsai]

Yup, very typical corrosion.

Hard to tell from your photo but that hidden bolt is almost a vertical drop from where the engine temp sensor is. You have to do it by feel. Should not give you much trouble though.

You can use a syringe or alike to suck out as much power steering fluid as you can. I did and no fluid came out when I loosen (but not remove) that collar circled in red. The reservoir only needs to tilt a bit anticlockwise for the ac compressor to clear it.

[MarkC]

So I've rotated the reservoir, undone all 3 bolts (removed the front 2 to ensure they aren't catching), but still can't remove the AC Compressor.

I can rotate L-R, and pull forward 1/4" and lift the front. Think the rear bolt is catching and not clearing the threads. One of the AC lines catches on the inlet, but don't think that's the problem.

Any ideas?
Mark

[MarkC]

Solved. Here is the offending cable out of the car, waiting for the new part arrival.

For me the bolt on the rear of the compressor has to come out (who knows how I'm going to get it back in), see picture - there's a bracket that connects the bolt (red circle) to one of the refrigerant lines that is just not reachable. On the refrigerant side It has a 10mm bolt on one side and a 5.5 female hex on the other (yellow circle), but neither location is accessible unless you have 5 year old's hands.

Mark

[Ahsai]

Good job getting that sucker out.

[britdave]

Guys, I think you may have solved my 2 year long problem in my 2002 911 C2 ! :thankyou:

Briefly, the alternator, is not charging the battery the way it should,especially after driving for a while. I have mentioned this problem in another post elsewhere on Renn Tec. Initial start up, it's putting out "about" 13.3 to 13.6 volts, then after about 3 or 4 miles (motor warming up of course) it starts delivering 13.20 , 13.10 , then a while later, about 12 .90 12.80 ,and even less, and of course that 13.0 and below, triggers the red light on my mini cigarette lighter voltage output indicator/meter (when it's above 13.10 it's yellow, and has to be about 13.40 to show green and charging correctly)

I've changed the battery, even got a new larger one with more cranking amps, removed the alternator, had it bench tested, and the guy put in a newer updated voltage regulator , so both battery and alternator are fine. Now more than ever I believe this is the culprit, that **** :cursing: alternator/starter wire !

I'm not sure if I can do all described above as my mechanical abilities are somewhat limited, so I'll probably just take my 2002 996 C2 to a dealer, and ask them how much $$$ :eek: they would charge me to replace this wire, any idea ?

I'm sure after they do this, all will be fine, unless it's the ground strap ? Is this a common problem, especially as when the motor warms up ? Thanks, I hope this will solve my problem, and the dealer doesn't fleece me $$$ that bad :rolleyes: any thoughts ?

Cheers Dave.

[britdave]

Anyone got anything to add to this alternator problem, where it doesn't put out what it should, especially after a few miles, when the motor heats up ? Any other advice, or theories on this issue will be most welcome, before I do the old 'Trial & error tactics ? I see I'm not the only one that has this baffling issue ??? Thanks Dave.

[Ahsai]

Anyone got anything to add to this alternator problem, where it doesn't put out what it should, especially after a few miles, when the motor heats up ? Any other advice, or theories on this issue will be most welcome, before I do the old 'Trial & error tactics ? I see I'm not the only one that has this baffling issue ??? Thanks Dave.

Dave, no need to trail and error. All you need is a $15 multimeter to measure a few points for voltage drop. If you have already replaced your alternator, then it's likely your starter cable but again only way to be 100% sure is to do some measurements.

You can use a jumper cable to connect the airbox negative bolt and the engine (exhaust will be fine). If you see improvements, that means you ground strap is bad.

[britdave]

Great thanks a lot ! Thats one I had not thought of ? DC

[MarkC]

Returning from a long business trip I started to put everything back together today. Right now I'm going through fiddling with the alternator reinstall. I remember how tricky that was last time.

Updates:

The first image shows how to locate the rear bolt on the AC Compressor. I've removed my wedding ring and slid the solid freon line between my 3rd and 4th fingers (counting thumb as #1) highlighted by the yellow hand drawn lines. By doing so you should be able to touch the head of the bolt.

The second image is another shot from beteen the intake runners.

The 3rd shot shows how I'm holding my phone in movie mode with my left hand (power lead because my battery is nearly dead) and have my fingers between the solid AC line, while my right hand is holding the top of the bolt. I can see from the phone/camera exactly where the bolt is and my left hand fingers can nudge it into place.

The next 2 pictures just show the camera/phone location clearer.

The last picture shows the rear bolt angle the same as the front 2 as the extension bar lies between the intake runners.

For a video see the follow up post. I ended up repeating the whole procedure due to dropping the temperature sensor rubber grommet behind the AC Compressor during re-install. I can confirm the AC Compressor can be removed in 5 minutes and installed in about 7.

Mark

[Ahsai]

So did the new cable fix your dropping voltage issue?

[MarkC]

Yes thank you (photo is a snap shot with lights running).

Took 20 minutes Friday night to wiggle the alternator back in, but then found a snapped vacuum line - the one that runs to the far side of the engine, so $4 for a rubber 2" x 1/4" vacuum link later + 20 minutes Saturday morning to re-assemble the intake plenum, throttle body and air intake and we're back in business.

I had a flutter when the car first started because it wouldn't rev, no response from throttle. Obviously I hadn't completely connected the wire for the throttle body, plus had some idle hunting when warm (750-800 rpm) but there were still loose air connections.

I still have a slight idle flutter, 4 seconds at 750rpm then a little rise to maybe 775 and then back down to 750. So may have too take another look at those universal clips around the intake plenum.

I actually think this job can be done now, without the alternator being removed and in under 2 hours start to finish (air box, throttle body, intake plenum, wire off rear of alternator, wire off starter, bolts off compressor, loosen power steering reservoir, pull out wire. Hindsight is always 20/20.

If anyone in Southern California needs help on this one, just PM me, I may be able to come round to help. Will try to add a complete write up later this week - shame I can't add the video to show the rear AC Compressor bolt, but will probably just dump to You-Tube and link to it.

Thanks

Mark

[Ahsai]

Well done! Good to see the solid 14v there.

[drspyros]

Hello,

I think that i have the same problem...but not sure ;)

That's why i want to ask you a question.

Now that you have fix the problem the volts are about 14 as i saw at the photos.

But when you turn on the lights, air condition and heating seats all together, does the voltage goes down to 13v lets say? Or it still stays at 14 volts?

Thanks in advance!

[MarkC]

The dash display gauge when the engine is hot now drops to about 13.7v volts with lights, heater, stereo, indicator & wipers on, but my gauge under reads, so will really be closer to 14v. Never drops to where it was before. The picture above is with the engine hot, at night with the lights and heater on.

Previously when the engine was cold the gauge displayed 13.5v, but when warm would drop to hover around 12v. I had been driving with the rear wing up for several months to keep the cables cooler.

For diagnostics follow Ahsai's post, #9 in this thread. The wire I changed shows up in test #3 (between A & J in his diagram).

http://www.renntech.org/forums/topic/44471-voltage-regulator-affected-by-heat-hence-low-voltage/#entry240001

To complete the testing follow Ahsai's post, #15 in this thread. There is no danger of causing damage as we are only testing loss due to the cables, there is little or no current plus the rear of the alternator is all plastic except for the bolt the starter cable is attached to so there is nothing to 'catch' on. You can stab around with the wire without worry. I'd still suggest finding some kind of inspection mirror (ladies make up mirror also works).

http://www.renntech.org/forums/topic/44652-alternator-terminal-b-access/

Hope this helps.

Mark

[drspyros]

Thanks a lot for the help. I try to fix this problem as well as other problems i have.

Thanks again!

[Gary S K Lee]

my 02 C4S's battery just died on me...i tried jump starting it but it died shortly after. Is that mean the battery is dead or the alternator is not working?? It just happened over night without any symtoms.

[JFP in PA]

my 02 C4S's battery just died on me...i tried jump starting it but it died shortly after. Is that mean the battery is dead or the alternator is not working?? It just happened over night without any symtoms.

Hard to say without more data. I'd get the battery load tested, and also have the alternator output voltage tested.

[injurylawyer]

I have to thank you and everyone who contributed to this thread. I am really grateful for the valuable information shared.

I purchased a '99 996 C2 in October 2014. Less than 10k miles before I purchased the car, the engine was replaced on the car by the previous owner professionally with a complete rebuild using a '01 block, L&N Engineering Nickies upgrading the bore from 3.4L to 3.6L, forged pistons and their IMS upgrade.

I had the exact problem happening on my car. Thinking it was the alternator, starter, voltage regulator, battery, etc., I was ready to endure a massive repair bill one way or the other.

However, going through the service records carefully, I then recognizing that only 5,000 miles had passed since the alternator was replaced with a new one, I became suspicious...

At that time, a new cable was installed and it was part number 99660701901...the older number Porsche had.

Curious, I sprayed a little WD-40 on the contacts at the starter and the + jump pole of the cable and the voltage increased, at least when cold and then the resistance of the heat when the engine warmed up made the voltage drop just like all the rest of you experienced...I knew something else had to be going on.

I too contacted Sunset Porsche and gave my VIN. I got the updated/upgraded part No. 99660701903...I had the parts specialist check and he indicated that he was aware of the other number but to go with this one....how right he was.

It took about a week to get the part in. Just as you said, about $42!

When bringing it back to the indie shop that had been servicing the car for the prior owner and actually did the engine rebuild, I brought the cable with me. Unlike other shops that whine about not wanting to install a 'customer provided part', since it was a genuine Porsche part, from a dealership no-less, they actually thanked me for having it.

However, to be on the safe side, they ran all the electrical tests that confirmed our hunch. The alternator/voltage regulator, battery and starter were all good.

Thereafter, the plan was to install the cable and then retest and if necessary do whatever else was needed. It turns out, nothing else was...

The previous cable had actually 'melted' in certain areas...they apologized for using the older part 99660701901 when replacing the alternator for the previous owner because their supplier did not have the new part number 99660701903, which they admittedly stated had some noticeable differences at the terminals and a bit in the length. They say it happens a lot when an older part is sitting on a shelf and the supplier moves what they have...

Makes me think that the changed configuration of the part and the trouble that we all share, the part should have been an optional recall.

Overall, between the testing, removing of the old one, installation of the new one, retesting, and closing the project out, they put in about 4 hours but lucky me, I was charged for only 2.8 hours which is more than fair for the work done.

My results are the same....an overall increase in voltage...nearly 1 1/2 volts making it run in the same range as you specified (as it should).

Once more, without the direction of your thread, and the contribution of all of you, I would not have had the insight to target the problem and arrive at a simple and cost effective solution.

Thank you.

 

:notworthy:

Edited May 8, 2015 by injurylawyer