No charge and no start

[DeRRis]

Hey guys I need your help. My battery isn’t charging and I’m sort of lost as to why. Oh and I’m going on a epic trip through the Alps in a weeks time so I need to get this fixed!

I’ll start from the beginning. On my 1986 911 3.2 Carrera I had a battery fail on me so I changed that. Just to be sure I also changed the fan belt as it was getting old. While changing the fan belt I noticed that there was some play on the fan/alternator shaft. I couldn’t ignore that so I got a brand new Valeo alternator (A14N67 90A). I installed that. And it worked like a dream and I had 14,4 volts at the battery.

Now 500 miles later my battery isn’t charging 12.2 volts at the battery but the charge light on the dash does go out. But here it gets bizarre. When I charge my battery with a remote charger it starts right up. When I take a full battery out of my other car it starts once. If I shut the ignition and I try to start again I just get a click. When I hook up another battery with jumper cables it fires right up. And if I take that battery out of the Porsche and put it in my Land Rover Freelander TD4 it has no problem starting the Landy.

The starter motor is maybe a year old and all the wires are clean and tight.

Any suggestions or methodical plan is greatly appreciated because like I said I’m going on a epic trip with 15 other old Porsches.

Thanks

[eimkeith]

How's your ground cable?


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[DeRRis]

Originally Posted by eimkeith

How's your ground cable?


Sent from my iPhone using Tapatalk

The one on the gearbox is brand new and the one in the trunk looks okay. But I'll measure to see if there is any resistance.

[T77911S]

looks don't do it.

need to remove it and clean it. same with tranny ground strap.
also check cable on starter.

did you connect the ground strap from the alternator to the engine

[DeRRis]

So I've checked the + cable from the starter motor to the battery and I have no resistance so the cable should be good. I've also checked from the gearbox to the - cable on the battery there I also have no resistance.

To me that says that my cables are good. Right?

[DeRRis]

Originally Posted by T77911S

looks don't do it.

did you connect the ground strap from the alternator to the engine

Yes I connected the Red (+) Brown (ground) and blue (charge) wires back on the alternator.

[DeRRis]

What's making my head spin the most is the fact that the battery won't start my Porsche without "help" but it will start a Land Rover Diesel!

BTW the starter motor isn't slow or anything it's either a click or she goes like the clappers.

[pete3799]

Pretty sure you have a ground problem.
Is the 12.2 volts at the battery with the motor running?

[DeRRis]

Yes it is. So why would it start when I help it with a secundairy battery.

I'll buy a new ground cable tommorow to eliminate that.

[pmax]

Originally Posted by DeRRis

What's making my head spin the most is the fact that the battery won't start my Porsche without "help" but it will start a Land Rover Diesel!

Modern high torque low current starter is the reason for the tinny starting sound of the latter as opposed to the low rumble of the 911.

[DeRRis]

Okay so that's like comparing apples to oranges.

[pete3799]

When I bought my car the only way it would start was with jumper cables attached.
Removed and cleaned the trans. ground strap and never had the problem again.

The charging voltage issue may be unrelated.
How old is the battery?

[jlex]

That transmission ground strap is pretty critical. About one time out of ten, my starter wouldn't go, just a click or two. Thought it was a bad starter but decided to replace the ground strap just in case. Starter has been 100% ever since

[DeRRis]

Originally Posted by pete3799

How old is the battery?

The battery is a brand new Varta 72Ah.

Today I'll buy two new ground straps and clean al the contacts. I'll let you guys know.

Thanks

[Quicksilver]

If you are only getting 12.2 volts when running and a short while ago you were getting 14.4 I'd say that the new alternator has an issue but I would test it first.

First up I'd check the condition of the ground and the positive cable at the alternator, the transmission ground strap, and the battery ground strap.
- Note: Just because you don't have resistance when checking with a meter doesn't mean you don't have an issue. If a cable has broken down inside so that a lot of the strands have broken you will still see no resistance from the negligible current from a multimeter. But when you start pushing amps through the same connection for charging or spinning the starter, that is a whole different story.

If jumping the car or charging the battery makes it easily come to life that would mean it is less likely that it is the battery's circuit to the starter. That would put the alternator and its wiring higher on the list.
If you can hook up a wire at the alternator and check the running voltage there it will quickly tell you if you have a charging issue.

[mysocal911]

Measure the voltage at the alternator light, which will be a very good indication of what the
actual alternator output is at the alternator B+ terminal. If the voltage there is much greater,
about 1 - 1.5V, than the voltage at the starter, then there's a connection problem at the
alternator B+ wire (crimped connector) or the crimped connector at the starter from the
alternator.

[T77911S]

Originally Posted by DeRRis

What's making my head spin the most is the fact that the battery won't start my Porsche without "help" but it will start a Land Rover Diesel!

BTW the starter motor isn't slow or anything it's either a click or she goes like the clappers.

hi resistance.
2 batteries provide enough current to overcome the resistance.

the solenoid requires a lot of current to pull in. if there is no "click" from the starter look at this path.
if it clicks but does not turn over it could be a bad solenoid or you have a bad connection in the main power system. I leaned towards this since you said you have charging issues too.
if the battery cant provide power to the car, then the car( alternator) cant provide power to the battery.


there are 2 red wires on the starter. one from the alt, the other from the battery.
ALL the connections HAVE to be clean.
what do you battery terminals look like? are they the factory molded type or are they the crappy replacement terminals that clamp onto the battery cable?
are the cables tight on the battery. give them a twist and see if they turn. don't damage the battery.

if you have no click, check power at the yellow wire at the starter. you might do this anyway. use a test light. compare the yellow wire while starting to the battery wire at the starter. should be just as bright. I don't suggest a MM. a MM can read 12v but there not be enough current to pull in the starter.

[mysocal911]

Originally Posted by T77911S

hi resistance.
2 batteries provide enough current to overcome the resistance.

It's simple! Just disconnect the in-car battery and use the jumper battery to crank the engine.
If the engine cranks OK with just the jumper battery, then the in-car battery is too weak by itself,
and there's NO voltage drop (resistance) from the front to the rear.

Originally Posted by T77911S

current to overcome the resistance

Current doesn't "overcome" resistance, it's higher voltage that "overcomes" resistance,
i.e. adequate voltage.

[DeRRis]

Well guys if you ever come to Holland the beers are on me! I changed the Battery ground cable, cleaned the body terminal and she fired right up. I’ve got 14.4 volts at the battery again so I’m happy. I’ve started her half a dozen times and she runs instantly.

As a precaution I also changed the gearbox ground strap so I should be safe for the moment. Looks like I’ll have to include this in some sort of regular maintenance. I still cannot get my head around the fact that such a cheap part can cause so much grief but I won’t dwell on that!

Thanks again

[Luccia at Pelican Parts]

whoo-hoo go Pelican community! So happy they were able to help you find the culprit. Seems to be a popular discussion in our electrical troubleshooting article here as well: Porsche 911 Electrical Problem Troubleshooting | Pelican Parts DIY Maintenance Article. Glad you got it figured out and I do hope you enjoy your trip through the Alps!