On-and-off charging problem at start-up

[CatsEyes]

Folks,

I had a mammoth thread about what turned out to be alternator and other issues a while back. Apologies: I'll try to not repeat that here!

I have what presents itself as an intermittent power drain that affects start-up. It comes and goes, but at the moment is with me all the time.

Sometimes my battery reads about 12.10v with the engine off; at other times (from memory) about 12.4 or more.

In the former case, when I start the engine, the battery voltage drops to around 11.5, and the charging gauge sits just above 10. The car labours a bit at idle, lacks power initially, and the lights are dim. Then, the moment I hit about 2500 revs or so everything instantly springs back to life. The charge gauge leaps up and hits about 12.5, the lights go bright etc.

In the latter case (when the 'off' battery reading is good) everything is fine at start-up, and with the engine running at idle the battery reads about 13.5 or so.

The alternator was overhauled recently, and the garage says it tests well. The wiring and connections there look good to me.

I have pulled fuses left, right and centre, but can't find a culprit. I've been under the car and checked and cleaned the wires and connections at the starter-motor, but all looks good there.

Recently I unearthed some so-so home-wiring from a previous owner (after-market immobiliser and stereo), and replaced it. (The immobiliser wiring went through the ignition switch, of course, so I was expecting that to be related.) After that it seemed the problem had gone. But no, it's returned again.

It's not the worst problem to have out in the country, but it's a pain if I have to start and then idle for long periods in city traffic, because the plugs really aren't getting a good spark.

Any other suggestions? I've run out of ideas for the moment.

Thanks in advance.

[Cocacolakidd]

Sounds like the voltage regulator at the alternator, but if that checks out to be good could also be a faulty battery that's not holding a good charge - Try replacing the battery with a known good one and see what happens...

[John_AZ]

CatsEyes,

I thought the earlier "long" post was quite informative.
Many of the replies offered solutions:

http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/621296-car-died-mid-journey-alternator-confused.html

Many electrical problems are either bad grounds or old cables and connectors.
The problems got so severe that a tech pro on Rennlist began to make new battery harnesses for the 944---IceShark . His kits were of the highest quality materials and sold for up to $500 after he died.
There is a current member on Rennlist that bought the remaining IceShark inventory and sells the kit for $285. Read more here:

IceShark Cable Kits... - Rennlist Discussion Forums

I owned early 924s and they were notorious for poor battery cables and grounds. The first repair was always to replace the battery cables with thicker guage wires.

I have a second ground wire on the '87S from the alternator top hold down bolt to the battery negative chassis ground on the firewall. The bolt that attaches the short negative cable can be lengthened to go into the engine compartment. Add a nut and there is a natural connection--no modification.

This last weekend, I spent a couple hours on a similiar problem, why was my starter getting sluggish and the battery not getting a full charge.

I ran the Clarks test on abnormal battery drain. 8.95ma = clock and radio presets= perfect

I then went and tested my wires using this rebuilders information:
Reduce Warranties with Battery & Voltage Drop Tests | AIM

I had a voltage drop from the starter to the battery POS connection.

I cut the POS cable connector in half and found on the inside of the crimp, there was corrosion and oxidation where the copper wires were crimped.

I went to NAPA and bought the military cable end and copper connector. My starter now "jumps" to quick start and the battery has stayed at full charge:



Keep trying to find the battery drain.
Upgrade your cables. They have to be OEM or thicker. Never buy a lower guage wire from an off the shelf supplier.

Some members even remove the alternator to starter cable and go direct from the alternator to the battery. This removes the connection at the starter. YMMV
Not suggesting this mod but at least check the cables and battery clamps. If you have acid corrosion on the cables --repair or replace.

GL
John

[CatsEyes]

Thanks, folks.

John: I may have expressed myself badly. The previous thread was very helpful, and I used the advice as well as I was able. I'm a late-bloomer with this stuff, and my mechanical knowledge is still very thin. I'm just a bloke who fell in love with a car and realises it needs a lot of careful maintenance, which will have to be done by me.

All I meant was that the previous thread was large out of proportion to the complexity of the eventual solution (alternator), and I was sorry if that wasted other people's time.

Both the suggestions are excellent ones: I will indeed run an additional ground from the alternator to a ground-point. And while I had checked the battery cables carefully, I had not cut open the copper connectors, so there could well be corrosion in there. (The hatch was clearly leaking badly at some point in the car's life, though it seals well now, thanks to the last PO.) I'm also working my way through the 'Power in Motion' page.

I should also mention that it's a RHD Euro-spec car (as they all are down here), and so the battery is above the left rear wheel-well in the hatch (passenger side). Hence there's no battery ground-point in the engine bay. The battery cables are massive, BTW. Don't think that's the issue. I'd add also that I have now cleaned every ground I could find around the car, which hopefully is all of them. (The Haynes manual diagram and my Euro-spec car don't match.)

Kid: I doubt it's the battery, and don't have a spare. Here the right battery-type for the 944 is considered 'exotic' and costs more than $200, so I don't want to replace unless there's a sound reason. And I did check out the VR after my alternator incident.

Also, the PO, in the interests of full-disclosure, did explain to me a problem he'd had that corresponds very closely to these symptoms. He said he'd changed the battery, without effect, but that problem eventually 'just went away'. Which obviously it didn't. It just took a while to resurface again.

Thanks for the all help, both of you.

[CatsEyes]

Quick update on this one.

I cleaned and re-did the battery cable. Don't think that was the issue: looked OK, actually.

I did have to buy a new battery in hte end: it was really struggling to hold a charge. Sorry, CCK: I should have listened to you on that one! now at least I have a good 12.6V+ with the engine off.

Problem is lessened, but still hasn't gone away.

I'll have a good look at the alternator next weekend, when I have a bit of spare time. And run the extra ground, as suggested by John.

Thanks again, folks.

[dpoul34]

I have the same problem still on my 87 NA. Sometimes start, sometimes not, and sometimes the battery has a great charge, go out driving for hours. Try to start it up the following morning, and nothing - have to jump it to get it to go. A battery that tests upward of 12.5+ volts at night is a mere 11 the following morning and the battery is a new INterstate.

I have new battery cables equivalent to IceShark's set up but have yet to install them. The other issue that was presented to me as a fault to no start issues was testing/replacing the reference sensors in the car.

I'll be following this to see how you make out. I'm hoping your issues work out to the positive.

[CatsEyes]

Thanks, dpoul.

In case it helps at all, my battery seemingly deteriorated very fast at the end. One week I was getting marginal readings between 12 and 12.4 with the ignition off. A week later, I was working on the pop-up headlamps (if you keep them up with the ignition off the parking lights stay on, producing a moderate battery drain), and the battery quickly fell to below 11V.

Just to repeat, though: I now have a brand-new battery giving a good 12.6V with ignition off, all the time. And yet the problem is still there, if somewhat less marked. In fact, every time I turn the key to 'on' the meter in the dash has a slightly different reading, anywhere from about 12.3 down to 10.5. (Of ocurse, the gauge itself may not be accurate - none of mine are, exactly, except maybe the tacho! - but the differences presumably are meaningful).

I'll keep at the alternator angle, aided by John_AZ's link here:

Reduce Warranties with Battery & Voltage Drop Tests | AIM

[dpoul34]

That's how mine is on almost every start - way below 12V on the gauge. Sometimes it turns over, sometimes it doesn't. Quite frustrating when you think of all the money already invested.

[Arthropraxis]

I was having trouble with my alternator charging and it turned out to be the factory alarm. The alternator has a path through the alarm. I didn't check out your last post about your problem, it may have been suggested earlier.

[CatsEyes]

Originally Posted by Arthropraxis

I was having trouble with my alternator charging and it turned out to be the factory alarm. The alternator has a path through the alarm. I didn't check out your last post about your problem, it may have been suggested earlier.

No, this wasn't suggested, as I recall.

How did you fix it: disable the alarm? Or was it just wiring?

A PO home-installed an aftermarket immobiliser, and I keep having a bad feeling that's involved. But can't see any obvious issues there, having checked and fixed the wiring.

Thanks for the suggestion!

[CatsEyes]

Hi folks,

A quick update for this old thread on irregular alternator readings at start-up. Both for my own sake (after advice!) and for others who have reported similar problems in the past.

A recent development seems to have narrowed-down my problem (though I'm still not 100% sure what it is).

At start-up I now have one of two experiences: either

1. the voltage gauge in the dash starts low, but pops straight up to 12V+ or so as the engine starts; or

2. The voltage gauge starts low, and there's a short period of belt squeal (varying from a couple of seconds to longer) while the gauge struggles to head up to 12V, and either succeeds or doesn't.

After 2., if I rev the engine to about 2k revs the gauge then instantly pops up to 12v+. Sometimes with squeal, sometimes not. (Not advisable every start!) No squeal once the engine is running.

This is the latest instalment in a long-standing problem, which became acute when the a/c compressor started to flex on its bolts at one point (tired old bolts), and the belt wouldn't stay tight. One day in traffic the car died altogether.

I had the alternator reconditioned and the a/c compressor re-attached. Couldn't find an affordable compressor at the time, though I have located a second-hand one now.

The battery is newish, and is behaving normally with the engine off, and once the gauge gets to 12v+. (The previous battery symptoms were with a dying battery, which led me astray.)

Both alternator and power-steering belts are new, and I have adjusted them so they feel pretty well perfect. So the squeal is a mystery, on the face of it.

A couple of possibilities occur to me:

1. Either the alternator or the compressor are not spinning freely, or are otherwise damaged.

2. There is still some flexing of one or other on their mounts (not discernible by touch with the engine off).

I'll have the compressor with me in a week or so, and that should narrow things down. I fear I'll need to look for a new alternator as well, though, and funds are tight right now.

So any other suggestions very welcome!

[Cocacolakidd]

Just throwing out ideas for consideration -

1.) The Alternator Gauge in the cluster may very well be faulty - Do check Voltages and conditions for awhile under hood to confirm accuracy of findings.

2.) AC Compressors are notorious for sticking, sluggishness, and or freezing up. With the belt off check for free spin on both the Alternator and AC Compressor.
It also may be possible that one of the brushes in the Alternator is faulty and causing the Alternator to be sluggish at start-up, and also not charging properly then ??

Curious note: Most if not all batteries in Porsches are a right hand positive post. Where as, at least here in the US, 99.9% of the batteries sold are left hand positive post. Maybe this is why they called it an exotic battery.

Have a down-under good day

[CatsEyes]

Thanks, Kid.

Yes, all your suggestions seem very logical. Both compressor and alternator seem to be spinning freely enough. But I am a bit concerned about the alternator: I never quite sorted out what the auto-electrician repaired on it, and will open it up again and have another look. (From memory, the VR looked brand-new, but couldn't see what else was done.)

As to the gauge, you may well be right: I don't trust it! But regardless of whether the actual readings are accurate, I'm presuming whatever reads as 10.5V is still less than whatever is reading as 12V, if you get my drift.

Tightening the alternator belt a bit little more seemed to improve the situation a bit. But I'm hesitant to tighten it too much, for fear of killing one or the other.

Don't know what I'd do without this forum...

Have an up-above good day!