What kind of battery did you install?

 

Hi DubyaTT

I installed a brand new 85A Made in Germany lead acid battery that is supposed to be good. It charged to 12.6V prior to installation.

 

What group size and manufacturer?

 

Niceguy,

Sorry to hear you're going thru all this aggravation with charge voltage especially since you said you just replaced alt. and bat. I've read on this forum of a similar occurrence (changed alt. and bat.) with same results. New ground cable at bat. fixed their problem. Not sure if you put a new alt. in or a rebuilt but the voltage still sounds lower that what it should be. After replacing my alt. VR, voltage was approx. 13.5 vdc with any load applied.

If it were a rebuilt alt., I'd reluctantly consider removing the alt. again, bring it to a local shop that especializes in electrical repair and have it tested. Not sure how reliable a rebuilt is over a new alt?

PS: I want to thank the members of this forum that responded to my alt. issue several weeks ago, and those that recommended removal and replacement of the VR as a DIY alternative to bringing it to a shop. It took me about 1.5 hrs. to remove it, 5 minutes to replace the VR and 2.5 hrs. to replace it. It only issue I had during the restallation, was that I over-torqued one of the pressure pipe to throttle body hose clamps. Had to remove it, and rework the screw attachment to the band in order to hold torque. Not sure what that torque is supposed to be.

 

Hi gillrich,

Thank you for your sympthy

I am really going thu disappointments one after another. First, battery, next alternator.

The alternator and volt regulator are brand new units and not rebuilt items. Moreover, the battery is a brand new, too. The difference I noticed with the new alternator is that the voltage now sits at 13.0V without any load (no ac, no music, only headlights). With AC on, the voltage goes down to 12.4V. But, however, these voltages have already been improved by about 0.5V on average.

I will look into the ground batt cable tonight. Do I have to buy a stock one or can I change to a DIY one?

Thanks

James

 

I would say replacement of the cable is a DIY task. As you mentioned a new alt. was installed and not a rebuilt, I'd be more reluctant to remove it again. Unless other forum members can provide additions recommendations, guess I'd contact a shop that deals mre specifically wih electrical systems and get their take on charge voltage level then bring the car in or take the alt. to them for testing.

 

An update

I just checked more voltages measured from

AC OFF & headlights OFF
+ve engine bay terminal & air filter bolt @ Idle = 13.2v (Not cold start)
directly from battery @ Idle = 12.9v

Does this indicate the 0.3v loss is talomg place between the alternator to the battery? How can I fix this or carry out further diagnosis?

Thanks a lot

James

 

I am sorry guys, I havent had time and the energy to check all the terminals according to minny. Thanks minny again! I will check those this weekend when I finally get enough sleep.

But, as my car was sat in traffic today, it got pretty hot, coolant to around 85 degrees, and the battery managed to drop to a worrying 11.8v (I have new battery, new alternator & regulator). As a result, the oil pressure also dropped to near 0 at idling. I thought the car was going to die but luckily it didnt before I made it home. The only good news is that once I left the traffic jam, I managed around 60mph and the voltage went back to 12.5v and the oil pressure went back to normal. Can this low voltage symptom when hot suggest any kind of problem lie within my car?

Many thanks and I am truly worried now....

 

I know most healthy 996s do see almost 14v. Could a slipping belt lead to a lower voltage when the engine is hot sitting in the traffic? As soon as I went on the motorway, the voltage climbed to its previous normal at 12.8v. If slipping belt cannot be the source of the issue, what can it be?

I started paying more attention to the sound of the belt. It does appear that sometimes it gives some strange sound like "gg gggg ggg git..." But, it doesnt have that sound all the time. Coincidentally, I do hear that same sound every time after washing my car though.

Tonight, I carefully cleaned both the positive and negative terminals of the battery and their leads. What I found was the resistance of the negative lead can sometimes be showing not zero at ohm measurements.

 

i throw my car on a trickle charger once a week whether it needs it or not, and my constant voltage is steady btw 14, maybe 13.8.. and never below 13 with a full load a/c/lights etc. just as another point of reference.

 

Thanks for the advice on a tickle charger 02996ttx50. I do plan to buy one but first I must try to sort out the low voltage problem once and for all and share the solution to this extremely small but annoying issue here with every 996 owners.

After the car has been driven, there is only around 0.3v difference between the alternator terminal (average 12.5-12.9v) to the battery itself (12.3-12.6v) at idle.

Just another thought, since I've never seen above 13.5v from the alternator even on a cold start, am I right to think that my new battery, new alternator and new regulator could be faulty? Or could it still only caused by a corroded earth or live cable between the alternator to the starter?

 

A big update!

I have finally borrowed some diesel grade jump leads from a friend and did all the measurements.

First, for the measure of voltage,

with the engine running from cold start,
across the transmission terminal +ve to the transmission oil tray -ve, 14.0v (the silver aluminum tranny oil tray).
battery @ 13.0v
engine terminal 13.3v.

with engine off,
voltage at transmission terminal 12.2v
across battery 12.2v
engine terminal 12.2v

Second, for the measurement of resistance,
alternator body to airfilter ground, multimeter @200 Ohm = 0.8 Ohm
alternator body to fuel filter @ 200 Ohm = 0.7 Ohm
alternator body to most metal parts @ 200 Ohm = 0.7 Ohm

Positive battery lead to alternator body @ 200 Ohm= 0.8 Ohm (But, it keeps dropping to 0 Ohm)
So, I tried multimeter @ 200 Ohm = 0 Ohm
Then, I tried @ 20k Ohm = 0.3 keep rising to 0.8 Ohm.

Third, with the engine idling, at full load (ac on & headlights on)
-ve battery terminal to alternator case = 1.0-1.2v (indicate a problem)

Some say when the voltage is greater than 0.01-0.02v, the ground circuit has too much resistance. Is this true?

Lastly, am I right to conclude that the alternator is producing healthy voltage? The issue is that the voltage cannot be transferred to the battery and the rest of the car.

With my poor electrical knowledge, could you advice me on which cable or ground to replace?

Thank you very much for your time and attention.

Best wishes,

James

 

Having thought that the ground strap is the culprit, I connected the alternator case to the airfilter bolt (ground terminal) using 1 jump lead and measured the following voltages. Here are the results:

Measured from a cold start
at the battery 13.0v (same, no change)
at the engine +ve terminal to airfilter bolt 13.3v (same, no change)
engine +ve terminal directly to the jump lead 14.0v (new finding)
*But, as soon as I placed the multimeter on the airfilter bolt again, the voltage goes down to 13.3v again.


So, I tried measuring the engine +ve terminal to alternator case 14.0v

In conclusion, the reading of the voltmeter on the dashboard 13.3v (again, no change)

At last, I unhooked everything and I removed the driver side rear wheel (Right Hand Drive), and looked very hard under the car and I couldnt find the ground strap as shown in the attachment, which is supposed to be near the cyclinder 6 ignition coil. There is a heat shield that stopped me from seeing the 3 ignition coils and the ground strap.

What should I do next?

Would it be a good idea to connect part of the engine case to the ground with 1 jump lead and measure again?

cheers mate

 

With the car running out your positive meter lead to ground lead at the battery and check for voltage to vehicle ground. I know it sounds weird, but if you have a suspect ground you may see voltage which would indicate a resistance to ground. Keep in mind that often simply reading a ground lead to ground will not show an issue because a ground problem often does not surface until current is higher.

As for your voltage problem, you may have a slipping alternator pulley. Did you replace it with new or use the old one? The pulleys are clutch type that can fail.

 

Thanks VAGscum for your reply,

Do you mean I should put the +ve lead of my multimeter to the battery negative lead and -ve lead of my multimeter to the car's ground, such as the engine case or alternator case or the car's sub frame or chassis using something like a couple of jump leads and measure the if any voltage exists? If any voltage exists when the engine is at idle, it is saying that the battery ground lead is the culprit.

The pulley in front of the alternator is also brand new, it came with the alternator.

Thank you for your input!