Weak Battery on Hot Start

[Andry]

I have a 2007 911 C2 with 94,000 Km.  Recently a problem has been creeping up on my.  The car starts fine when I don't use it for a while (few days).  However, when I drive it, then park and go to re-start after a few minutes (up to an hour or so), it's a very weak start -- the engine turns over slowly as if the battery was low.  I don't think that it's a battery issue -- I have a new Optima Red Top and use a "battery tender".  I've also tried a different battery with same results.

 

This is so frustrating.  The car starts strong the first time I start it but when I park it and go to re-start, it's very weak!!  I read a similar thread on this forum (but for a 2002 996 -- "Dead or weak Battery Issues").  Note that my car is not winter driven and has no rust.  All battery cables, including ground straps, are in top shape with no corrosion present.

 

Is this a starter problem or should I replace the alternator Voltage Regulator?  Any other ideas?  Please provide part numbers if possible (for a 997 C2).  I have a track day on Thursday and would love to solve this beforehand.

 

Thanks in advance!

 

[Ahsai]

The symptoms point to a bad starter or starter y-cable and other cables. The cables can be diagnosed with a voltmeter when a slow cranking condition occurs.

 

You can't always visually id a bad cable. It could look shinny but still fails. The only way is voltage drop tests.

Edited July 25, 2016 by Ahsai

[Andry]

I will look into those cables and do some voltage tests.  You mention the starter but not the Voltage Regulator (on the alternator).  Why would the starter behave differently on cold vs hot starts?  I would have thought that starters should be good for well over 100K km.  Other threads on this forum (www.renntech.org/forums/topic/43051-dead-or-weak-battery-issues/#comment-230288) specifically mention the regulator.  Have you heard anything about that?

 

Thanks.

 

Edited July 25, 2016 by Andry

[Ahsai]

If your voltage regulator is bad, you should have problem at cold start as well.

 

Electrical resistance increases on corroded contacts as temperature increases. The starter inside can have open windings or corroded solenoid contacts once warmed/hot. Mechanically it can also seize when it's too hot.

 

[Ahsai]

Btw, please check my write-up here 

 

[Andry]

Ahsai -- thanks for the reply.  I'll check into all of that (including your write-up) and will report on progress.  Looks like others are also running into this issue...

If anyone else has had similar problems recently -- feel free to chime in.

 

[JFP in PA]

This is a common hot weather complaint at the shop.  Porsche has actually updated the cables to help eliminate the problem.

[Andry]

Therefore, what both JFP and Ahsai are saying is to change the "Y" cable first and see if this resolves the problem.  Makes sense -- least expensive option first!  I like!

 

BTW, what's the part number for a 997 C2 (because Ahsai has a 996).  Thanks!!!

 

[JFP in PA]

4 minutes ago, Andry said:

Therefore, what both JFP and Ahsai are saying is to change the "Y" cable first and see if this resolves the problem.  Makes sense -- least expensive option first!  I like!

 

BTW, what's the part number for a 997 C2 (because Ahsai has a 996).  Thanks!!!

 

 

Actually, what we a both saying, if I can speak for Duncan, is to do a voltage drop test across the cables before changing anything.  That will tell you exactly where the problem lies, and what needs to be replaced. 

[Andry]

Of course I'll do the voltage drop test first -- that's a "no cost" approach which is always the best.   However, I suspect that something must be wrong since any car should start flawlessly either hot or cold.  It's just frustrating when an old clunker start first try beside you and the Porsche is coughing and spitting

 

[JFP in PA]

6 minutes ago, Andry said:

Of course I'll do the voltage drop test first -- that's a "no cost" approach which is always the best.   However, I suspect that something must be wrong since any car should start flawlessly either hot or cold.  It's just frustrating when an old clunker start first try beside you and the Porsche is coughing and spitting

 

 

To give you some idea of how common this problem is, Porsche actually released a TSB about the cables when they released the updated parts.  Soon as it gets hot, and it is 100F here today, we start getting calls with the same parameters.  Fortunately, the fix is both inexpensive and relatively easy.

[Andry]

Sorry to bother you again...  In case I find the cables to be my problem, what's the correct part number for my 2007 997 C2?  Can you point me to a place (site, manual, etc.) where I could get this info without troubling members on this forum?

 

Again, thanks for your patience with all my questions!

 

[JFP in PA]

55 minutes ago, Andry said:

Sorry to bother you again...  In case I find the cables to be my problem, what's the correct part number for my 2007 997 C2?  Can you point me to a place (site, manual, etc.) where I could get this info without troubling members on this forum?

 

Again, thanks for your patience with all my questions!

 

This should give you everything you need: Sunset Porsche parts catalog

[Andry]

Great!! Thanks a million!

[Ahsai]

2 hours ago, JFP in PA said:

 

Actually, what we a both saying, if I can speak for Duncan, is to do a voltage drop test across the cables before changing anything.  That will tell you exactly where the problem lies, and what needs to be replaced. 

Exactly. Thanks, John :)

[Andry]

Success!!    Here are the details of how the problem was solved.  The following tests were conducted:

1. Charging voltage at battery posts = 13.9V

2. Charging voltage at alternator = 14.5V

3. Voltage drop between alternator and side post of transmission = 0.3V

4. "Y" cable harness (mine is still the old p/n 997-607-018-02, new p/n is -03) was inspected with no visible corrosion at any point and had negligible resistance readout.

 

This lead me to suspect the battery (Optima Red Top) which has been in use for 4 years.  Optimas usually last a long time if you cycle charging with a "smart" battery charger (I use a CTEK), but in recent years I think that Optima's quality has significantly dropped.  I use my car only during the summer months (about 10K km per year) and store it the other 8 months with the battery hooked up to the charger.

 

In short -- I took the battery to my dealer and had them do a battery test.  They did it twice and it failed both times.

 

So, off to WalMart I went and bought an EverStart MAXX 94R/7H for CAD$137.97.  This seems to be a preference as recommended by many 997 users on various Porsche forums.  We'll see after a couple of years...

 

After testing out the car this afternoon -- all is good and I'm a happy camper ready for Track Days this Thursday!

 P.S.  Thanks to Ahsai (Duncan ?) and JFP in PA (John ?) for their help in steering me on the right path to success.

 

[Ahsai]

Glad to hear you got it sorted but I must say I was misled by this description :)

 

"I don't think that it's a battery issue -- I have a new Optima Red Top and use a "battery tender".  I've also tried a different battery with same results. "

[Andry]

You are correct -- when I re-read my post, I noticed that I did not convey the info properly.  What I mean to say was that the "different battery" was a separate new Optima Red Top which I have in one of my "classic" vehicles.  That Optima is new and hooked up to a battery tender.

 

What I did during my initial try at resolving the "hot start" problem was to disconnect that new Optima from the other vehicle and connect it via booster cables to the 997.  I now realize the faulty approach because the resistance in those long booster cables probably caused the same problem as the "dying battery" in the Porsche, i.e., very weak start.  Next time I'll run tests the proper way right from the get-go.  Live and learn!

 

[Ahsai]

Ah, it all makes sense now. Glad it was just the battery. Those cables while not expensive, they are a pain to get to.

[Roger Floydman]

My daily driver is a 2006 997.1 2S and i have also been having battery issues. Initially (6 months back) i had replaced the battery with a  EverStart MAXX 94R and thought the problem had gone away, but it started to get worse again. Warm starts very weak. Ended up buying a battery tender which is a pain as i live in a place without an electrical socket close to my car. So i took it into the dealer and they said the alternator was good & the battery was shot and i needed a new battery. I was surprised but hey, they are the pros right? So replaced battery with recommended Porsche battery and problem comes back soon after.

 

Dealer said that i don't drive the car enough ( i'm doing about 10 miles a day, mostly in traffic, max 20-30 mph ) but i find that hard to believe as i have driven many other cars over the years, most no where near as expensive as a 911 and none had similar battery issues.

 

The dealer did not mention anything about the TSB about the cables mentioned here. I'm assuming they checked the voltages as they charged enough for diag. labor costs.

 

Any advise appreciated.

 

[Hilux2400]

I had a cranking speed problem with mine (2003/996) and when I replaced the battery I put in a much larger one with higher cold cranking ability.  However, I still had problems at times.  The problem disappeared after I cleaned up the earth strap between the engine and frame. The one under the rear wheel arch.  Since then I only get the problem if I leave the car, not on charge, and unused for about 7/10 days depending on weather.  Then it's very slow to crank, but quite often starts.  If I drive it every day, even for short journeys it's OK. 

 

I find these cars quite strange from this cold cranking perspective. I have two Toyotas which will stand easily for a month unused and even longer.  

[Ahsai]

14 minutes ago, Roger Floydman said:

My daily driver is a 2006 997.1 2S and i have also been having battery issues. Initially (6 months back) i had replaced the battery with a  EverStart MAXX 94R and thought the problem had gone away, but it started to get worse again. Warm starts very weak. Ended up buying a battery tender which is a pain as i live in a place without an electrical socket close to my car. So i took it into the dealer and they said the alternator was good & the battery was shot and i needed a new battery. I was surprised but hey, they are the pros right? So replaced battery with recommended Porsche battery and problem comes back soon after.

 

Dealer said that i don't drive the car enough ( i'm doing about 10 miles a day, mostly in traffic, max 20-30 mph ) but i find that hard to believe as i have driven many other cars over the years, most no where near as expensive as a 911 and none had similar battery issues.

 

The dealer did not mention anything about the TSB about the cables mentioned here. I'm assuming they checked the voltages as they charged enough for diag. labor costs.

 

Any advise appreciated.

 

 

Sounds like the dealer has not diagnosed completely.

 

You really need to diagnose the following to be complete:

1) The battery

2) The charging system and all the cables between the battery and the starter and alternator

3) Any parasitic drain

[JFP in PA]

To follow up on what Ahsai has outlined, you need to:

 

1. Load test the battery
2. Voltage and load test the alternator
3. Check the voltage drop across the primary battery cables
4. You should have a 40-60 mA draw on the battery for about 1 hour or so after the car is shut off.  Any more than that and you have a parasitic drain on the system.

Lesson to be learned: Do not assume anything when it comes to diagnostics, even at the dealer.  You should have gotten a detailed break down of what they tested and what they found.  We regularly see cars that were just at the dealers, and they completely missed an obvious problem that I would expect an intern to catch.

[Roger Floydman]

Does anyone have a link to the TSB related to the cable issue? I wonder whether my 997 has the original cable. I think they replaced it with an improved version for the 997.2

[Roger Floydman]

2 minutes ago, JFP in PA said:

To follow up on what Ahsai has outlined, you need to:

 

1. Load test the battery
2. Voltage and load test the alternator
3. Check the voltage drop across the primary battery cables
4. You should have a 40-60 mA draw on the battery for about 1 hour or so after the car is shut off.  Any more than that and you have a parasitic drain on the system.

Lesson to be learned: Do not assume anything when it comes to diagnostics, even at the dealer.  You should have gotten a detailed break down of what they tested and what they found.  We regularly see cars that were just at the dealers, and they completely missed an obvious problem that I would expect an intern to catch.

Thanks all for the replies. I'll be heading back to the dealer.