Alternator Issues

BRP83SC · 06-07-2008, 04:33 PM

I am troubleshooting my SC electrical issue--the car does not start after sitting for a period of time.

Local garage tested and found no drain, but did not that the note that the reading on the multimeter was reading 13.45; that is, car running with multimeter on battery.

I replaced the alternator with a rebuilt, charged the battery and been running the car. The multimeter reading on the battery is 13.60.

I check the belt on the alternator and tension is good.

I am wondering if the connection(s) from the alternator to the battery are sound or I have a defective alternator?

Before contacting the place that sold me the rebuilt, is there any value in pulling the alternator hooking a couple of wires up to the alternator, put it together.

Then with the car running, take a reading off the two wires hooked up on the alternator?

Any thoughts?

ramonesfreak · ramonesfreak's Garage

im sure somebody here can help you. can you describe better what happens when you try to start it? totally dead? turn over? CDI sound is present? fuel pressure is present? green wire been damaged? etc...

BRP83SC · 06-11-2008, 09:52 PM

Bump (i have seen this in other posts, but am not sure what it does--maybe it good luck

)

Thanks Scott

After a while of driving (over a period of days), I will go out to drive the car and it will not start--dead battery.

When I purchase the car, I replaced the battery since it was about 4 years old. I conducted the battery drain test (i.e. hooked up a multimeter and pulled fuses to see if there drop) but did not detect a battery drain. Also, I did not have a situation with the door was ajar or the glove box left open to where a light burned

That is when I took it to a local Porsche shop where they did the battery drain test and found nothing; however, they said that the alternator was not properly charging the battery--the reading was ~12.87. The guy at the shop said that when the battery is charged the car will run for awhile, but after awhile it will not start since it is not being properly charged.

I purchased a rebuilt alternator and put it in the car--same problem, the car runs for about a week, then it will not start. With the new alternator, I am getting a 13.78 reading on the battery with the car running.

In all situations, the alternator light does not come on (only briefly when you start it)

I raised the car and cleaned the Engine/transmission to body strap and its connection points. I checked the connections at the starter which were tight. The battery was recharge to ~12.78.

On the solenoid, there was yellow wire with blue strip and a plain yellow wire. One thing I noticed was that there was a black wire spliced into the yellow wire prior to it being attached to the solenoid (picture below); I was not sure if this was part of the alarm system which appears to be aftermarket

In addition, I replaced the belt and have all six spaces--three on each side. the belt tension is within the specifications in all of the books (i.e. Bently, 101 projects...etc)

So fellow pelicans, I can only think of the possible situations:

1) The rebuilt alternator is no good; its a bosch
2) There is something wrong with the wiring between the alternator and the battery which is why i was thinking about removing the alternator; hooking a wire up to the positive side and one to the negative of the alternator; reinstall the alternator; start the car and take a reading of the two wires coming out from behind the alternator--this would give a true reading from the alternator??
3) something that I did not mention and/or think of

ANY help would be appreciated as this is starting to drive me nuts

Brad

mca · 06-12-2008, 04:28 PM

Hey Brad -

Maybe you answered this before, but did you have your battery replaced? Have you had it tested? I know you replaced it when you bought the car, but how long ago was that?

When my voltage regulator began to fail (wasn't a sudden, complete failure) it put a hurting on my battery. Apparently some of the "cells" were destroyed.

After switching to a new Optima all was good.

I suppose it is worth a try. You could always try it out and the return it if it doesn't solve the problem.

don gilbert · don gilbert's Garage

your descriptions are a little fuzzy, 13.8 at the batt with car running is good, 12.5 with car not running is good, does your light in the dash come on when key is turned to run (not start) position, its a skinny blue wire that excites the diodes and start the charging field, if bulb is burned out, most will not charge, if all is good i'll agree with mca and get an optima (they are awesome) be the way, one of those wire from that back of your starter sol. enegizes the cold start valve during cranking

BRP83SC · 06-12-2008, 08:58 PM

MCA: The battery is about a year old--if that. I was wondering about a bad cell. I will have the battery checked

Don: I ran the car out tonight for fuel; after that, I went for a spin of about 15 miles. When I pulled it into the garage and put a meter on the battery as it idle, the reading was 13.5. Yesterday, the reading was 13.8 while running. Now that you mention it, any number above 13.5 is acceptable. Yes, the alternator light comes on when I turn the key prior to start. Once started, the light shuts off

Any thoughts as to why I have a black wire feeding into the yellow as it connects to the solenoid and a black wire feeding into the yellow/blue wire as it connects to the solenoid?

The wiring diagram in Bentley does not show either of these black wires.

911pcars · 06-12-2008, 09:41 PM

With the engine running, switch all electrical accessories, lights, fans to ON. Observe the system voltage at the battery. Raising the idle speed should produce 14+ volts. If the alternator doesn't compensate for the increased electrical load, somethings wrong with the alternator or reguulator.

After the engine starts, the battery is just along for the ride. After the alternator recharges the battery (it discharges while cranking), all the electrical energy needed to run the vehicle is supplied by the alternator. If instead the battery supplies more than the alternator can, the red light goes on.

Sherwood

rick-l · 06-13-2008, 07:16 AM

Quote:

Originally Posted by BRP83SC

I conducted the battery drain test (i.e. hooked up a multimeter and pulled fuses to see if there drop) but did not detect a battery drain. Also, I did not have a situation with the door was ajar or the glove box left open to where a light burned

When you disconnect your negative cable and put your multimeter in series with the battery and the cable how many milli amps do you read?

911pcars · 06-13-2008, 10:27 AM

"Local garage tested and found no drain, but did not that the note that the reading on the multimeter was reading 13.45; that is, car running with multimeter on battery."

There could be some battery drainage issues as well (garage said negative, yes?), but this sounds like a charging issue - voltage generated by the alternator is insufficient to recharge battery. However, as long as vehicle load requirements are below charging voltage (battery not operating at a deficit), you're borderline ok if not extreme borderline.

Voltage at battery with engine ON should be 14+ volts.

Sherwood

cljsf · 06-13-2008, 10:53 AM

Brad,

I had a similar problem with my '87 Carrera. I thought of doing what you suggested about running wires to the alternator terminals. However, after looking at a wiring diagram, it turns out that the B+ terminal supplies current to both the starter and to the heater relay/motor (on your SC as well as my Carrera). You should be able to check the output of the alternator at the fuse board in the engine bay. With the engine running, compare the voltage there to the voltage at the battery. That should help you identify whether the alternator is not putting out enough voltage or whether the wire from the alternator to the starter is at fault. You might also see if the voltage changes with revs. Suggest you try these things and report back.

Also, in my case, it looks like I started out with a problem with the voltage regulator, but after that was fixed I didn't reinstall the alternator correctly. When I went to remove it a second time, I discovered the insulation on the ground wire connection had come loose and it looked as though the ground wire connector was actually touching the diodes running to the B+ terminal. I fully insulated all three connections to the alternator with electrical tape and when I reinstalled the alternator everything worked fine.

Hope this helps,

Charlie

BRP83SC · 06-13-2008, 03:37 PM

Thanks for the MUCH needed advice.

Rick, I will perform the test and report back; I am a little green with the multimeter tool (which is why I had the garage verify the test I initially performed)

Sherwood, Last night the reading with the car ON and idling was 13.5; if I do as you suggested (i.e. turn switch all electrical accessories, lights, fans to ON.) and raising the idle speed produces 14+ volts. Am I OK if the alternator responds with 14+ reading?

Charlie, I will look up the fuse # in your post in the Bently book and perform the test. I am glad I asked first

Brad

BRP83SC · 06-13-2008, 05:42 PM

I just fished one test:

Started the car, move the idle to 1500 and kept it there.

1) took a reading of 13.60
2) turned the head lights on; took a reading of 12.30
3) turned the head lights off; took a reading of 13.60

based on these results, Bentley book info, and advice on this post, it appears the alternator is still not providing enough juice--am I correct?

911pcars · 06-13-2008, 11:19 PM

Quote:

Originally Posted by BRP83SC

I just fished one test:

Started the car, move the idle to 1500 and kept it there.

1) took a reading of 13.60
2) turned the head lights on; took a reading of 12.30
3) turned the head lights off; took a reading of 13.60

based on these results, Bentley book info, and advice on this post, it appears the alternator is still not providing enough juice--am I correct?

With an electrical load ON (headlights), the alternator should supply the needed current with a 14+V charging rate. Since you only measured 12.3V, that indicates the alternator isn't charging (battery is discharging). The 13.6 volts is basically battery voltage. With the headlights ON for any length of time, the vehicle battery will discharge to the point where the engine won't run.

I'm not 100% condemning the alternator yet. Check the many electrical connections in the circuit and the regulator. For this, you'll need more test instruments (high current ammeter) most likely at an auto electrical shop,. Here's a check list of tests for the alternator:

http://www.smccd.net/accounts/mcafee/LabWorksheets/AlternatorDiagnosisWork.html

Some folks risk it and start replacing parts (alternator) to see if that works. Can get expensive.

Sherwood

BRP83SC · 06-14-2008, 07:35 AM

Quote:

Originally Posted by 911pcars

With an electrical load ON (headlights), the alternator should supply the needed current with a 14+V charging rate. Since you only measured 12.3V, that indicates the alternator isn't charging (battery is discharging). The 13.6 volts is basically battery voltage. With the headlights ON for any length of time, the vehicle battery will discharge to the point where the engine won't run.

I'm not 100% condemning the alternator yet. Check the many electrical connections in the circuit and the regulator. For this, you'll need more test instruments (high current ammeter) most likely at an auto electrical shop,. Here's a check list of tests for the alternator:

http://www.smccd.net/accounts/mcafee/LabWorksheets/AlternatorDiagnosisWork.html

Some folks risk it and start replacing parts (alternator) to see if that works. Can get expensive.

Sherwood

Thanks, some of these, I have already done, some I will need/perfer a shop (i.e. experienced tech) to carry out.

Looks like you reside in So Cal, any suggestions (i.e. ones that you feel comfortable recommending) on porsche shops.

rick-l · 06-14-2008, 08:42 AM

Quote:

Originally Posted by BRP83SC

I am troubleshooting my SC electrical issue--the car does not start after sitting for a period of time.

Again the first thing to check is if there is a drain on the battery with the car off. Your mechanic said there is no drain but some wrenches don't make good sparkies.

Just out of curiosity do your door lights work, a common source of this problem.

911pcars · 06-14-2008, 11:20 AM

"Looks like you reside in So Cal, any suggestions (i.e. ones that you feel comfortable recommending) on porsche shops."

I'm 200 miles north of you in the L.A. area. There are some guys in your area that can provide more useful information. Try Doug Wierenga (DW SD) or Mike Gagen (Ted) off the top of my head. Maybe others from SD area can chime in.

Sherwood

BRP83SC · 06-14-2008, 09:47 PM

Quote:

Originally Posted by rick-l

Again the first thing to check is if there is a drain on the battery with the car off. Your mechanic said there is no drain but some wrenches don't make good sparkies.

Just out of curiosity do your door lights work, a common source of this problem.

Understand what your statement--that all mechanics are created equal; they received the same results as I did, but I plan to run the drain test again.

Assuming you are referring to the light between the visors above the rear view mirror, I have the light set not to turn on when the door is open, but to answer your question, the light will come on when the passenger door is opened provide I have the console light toggled to that position. The drivers side door does not trigger the light to come on--it has an issue.

mca · 06-15-2008, 06:53 AM

I still can't believe you haven't tested your battery.

That is the easiest and most logical step.

Just think, if the battery is bad you have been stressing for days over nothing!

rick-l · 06-15-2008, 07:22 AM

Quote:

Originally Posted by BRP83SC

Assuming you are referring to the light between the visors above the rear view mirror, I have the light set not to turn on when the door is open,

There is a power window relay in the door light circuit that in some cars if the door doesn't open it stays on. This will drain the battery.

Quote:

Understand what your statement--that all mechanics are created equal; they received the same results as I did, but I plan to run the drain test again.

The drain on the battery would be measured in amps not volts. I haven't seen any numbers like that.

BRP83SC · 06-15-2008, 08:57 AM

Quote:

Originally Posted by mca

I still can't believe you haven't tested your battery.

That is the easiest and most logical step.

Just think, if the battery is bad you have been stressing for days over nothing!

That is the next test, I replaced the battery less than a year ago.

I was going to take the battery somewhere for a test.

As it was explained to me, by the garage, the battery is charged. You take it out for a drive, but since the alternator is not doing it's job (i.e. producing less than 14 while running), the car is functioning a bit off the battery. This will last a few days depending how much driving and how much the accessories are being used.

Eventually, you go out to start the car and nothing.

So, I have a fairly new battery, a new alternator, good belt tension, no drain (after me testing and the garage testing). The new battery was installed first, then the new alternator was installed.

As posted earlier, the alternator performance is suspect, but I am going to have both tested again.

Will report back on the test

Happy Father's Day