Bill Ball

Good point, Charley. The only direct observation I made is that the jump post showed only a couple of volts when the no power event was happening. So, it was rather poorly connected to the battery at that point, with the battery showing over 12V. I thought I had it solved when cleaning the positive post and clamp restored power, but the problem recurred a week later and persisted despite cleaning all the major junctions.

Bill Ball

Dave: I could be wrong, but my observations just don't fit a bad battery as it has not shown any abnormality in voltage when the car is otherwise dead, but I will verify that with some more testing....with eye protection.

outbackgeorgia

Bill,
Good point, but just pressing down on the pos post can restore power. Also, the same corrosion situation that occurs in the neg lead can also occur on the pos lead-corrosion under the insulation.
Sounds like your methodical troubleshooting will yield results soon. Intermittents are very frustrating.
Dave

SeanR

I know you've been there, but I had a car lately that had an airbag fault and it was only on left turns, when it was warm, and the A/C would quit working at the same time. It was all due to this:



If you look close you can see one wire with no insulation. What you can't see are the 4 others that are all close to touching each other.

Mrmerlin

When i find the red wire insulation cracking,
I put heat shrink on the thick red wire pictured,
same for the ABS red wire attached next to the ABS unit.

Bill since you replaced the ground cable there has to be a bad connection between the battery Positive terminal and the hot post.
I would swap in another battery to test this idea

Bill Ball

The saga continues....

The subject 87 S4 ran perfectly for a couple of months of daily use. Then, one morning there was no (or essential none - maybe a couple of volts) electrical power anywhere in the car. The owner waited a few hours, power reappeared and the car ran fine for several days.

I decided to take the car to my place and put it on the lift for further inspection of the main positive cable. I got a couple of miles down the highway when the car just died and again was totally dead electrically. This was the first time it died while driving, indicating for the first time that the alternator must have become disconnected as well.

The California Highway Patrol towed me off the highway for free. I was only stranded for maybe 5 minutes before the service truck showed up. It's a regular service they provide on some of the more busy corridors. Nice. Then I walked 3 miles back to the owner's house. We drove his other car back to the 87, and lo and behold it started up and I drove it back to his house.

A week or two later all power failed again in the driveway. Eventually it returned and started right up and the owner took it to a local automotive electrical shop that easily solved a few other electrical things with this car before.

It's been at the shop for 3 weeks. The electrician can find nothing wrong. He has not been able to reproduce the problem. The car has started and run fine the whole time. I discussed it with him and said almost everything points to a bad positive cable and/or engine harness. He said that unless he can recreate the problem, there is nothing he can do to diagnose it.

We're kinda stuck. Even though I've never measured poor voltage across the battery posts when the rest of the car had essentially no power (no more than 2-4 volts), swapping the battery is easy, not horribly expensive, and is one of the likely culprits ignoring my seemingly normal measurements across the posts.

Anyway, this continues to be a head-scratcher.

daveo90s4

Bill, can you get hold of a known good battery to starter cable and temporarily mount that (while leaving the original in place, but disconnected at each end). Might help in confirming whether the original cable is the cause of the problem or not.

dr bob

Bill--

My doofus diagnostics led me to replace the positive cable. I'd run test leads from the battery positive at the rear of the car to a meter, other side of the meter on the starter + post, or the CE positive. I was sure I was seeing voltage drops at times, but it wasn't consistent enough to draw a real conclusion. So I replaced the positive cable anyway just to it from the list.

I eventually replaced the ground strap at the battery and solved the low-battery-charging problem, But the diagnostiic for the positive cable is still a voltmeter between the battery + and the CE panel, then the jump post, then the starter positive post. When you no longer see a voltage drop, step back one test and you have the culprit.

FYI, I made the long jumpers from some 18ga non-exotic wire, added a ring terminal at one end of each, and used some alligator-clip test leads from the meter drawer to connect them to the meter. Figured the thin wire would self-destruct if it faulted to ground accidentally. Could have added a couple fuses pretty easily, but was feeling pretty lucky that day. You've had those days I'm sure, the ones that usually end with a bit of smoke and the unmistakable fragrance of charred insulation.

Bill Ball

Well, here we are again....the problem continues. Seemed to be dormant for months. Here's what happened today.

1. Started and drove fine for 20 miles. Only odd thing was the ABS and ! lights flickered and then came on steady during the ride. When I got to the destination, I stopped and restarted the car and the ABS and ! lights stayed off.

2. Restarted several times while working on the car.

3. Started to drive the car back to the owner. Less than a mile into the drive I noticed the voltage gauge fluctuating, bouncing off 16V. And the tachometer zoomed up to 3-4000 RPM while I was idling at normal idle RPM. So, I knew again that somehow the battery was no longer in the circuit.

4. I pulled over, killed the ignition. Attempted to restart - NO ELECTRICAL POWER ANYWHERE. Well the digital clock showed its numbers, but it would fade when I turned the ignition to start the car. No lights at all. Nothing.

5. Got out, undid the ground cable from the rear deck - no sparks at all (no power). Opened the battery door, fiddled. Power came back and car started.

NOTE: BATTERY IS NEW - not the battery we had when this problem started.

Other things done already.
- Ground cable was replaced
- All major grounds cleaned.
- Jump post checked.
- Terminals cleaned.
- Connectors at starter and alternator cleaned.

The problem is so transient, it's hard to evaluate. I think the battery box manipulation is a coincidence. I can wiggle the posts and cables and bounce the battery around (after I remove the hold down beacket) till the cows come home but I cannot replicate the problem. We had the car at an automotive electrical shop for 2 weeks and the guy, who is good at what he does, could find nothing wrong and could not replicate the problem.

I think Alan has given me some advice in post 24, but I've manipulated the engine harness and alternator cables and, again, cannot replicate the problem.

Now, we did find a while back that one of the smaller wires terminals on the positive battery post was at least intermittently shorting against the battery box lid. Of course that shorts the battery, but the evidence was just a tiny burn mark on the underside of the lid, no serious arcing. Anyway, I took car of that so the post is fully covered, and that battery was replaced. I don't think this accounted for what happened then and it can't account for it anymore. Even if this damaged one of the attached components, what could account for loss of all electrical power INTERMITTENTLY? To be clear - the is a small amount of power - 1-2 volts measured at the jump post, enough to power the clock but nothing else. Also, it appears it has to be something that would isolate the battery from the charging circuit.

Frustrating. Hard to test since in almost all cases the problem resolves fairly quickly and doesn't recur for weeks to months.

Mrmerlin

Bill a WAG , I would suggest to check the ABS wire where it connects with the Phillips screw near the PS reservoir check that the wire isnt worn through,
trace this wire bask into the harness junction where it passes through the timing cover

infact why not add a few layers of heat shrink to it make sure the battery is disconnected first

MainePorsche

Bill,
I had a similar and perplexing issue occur one time. Car was running very well at the time. I had done some work 2-3 months prior (hint). I was pulling off the street at slow speed into a gas station. R front wheel up incline first, and as soon as the car was somewhat angulated it quietly turned off. I attempted to start and absolutely NO electricity. As I was in a bad position in the gas station, I pushed her to a good area. Walked back to the car, opened the door, and lights on... then she started right up. Got my gas and made it home to my garage. Got her up and started the inspection. The work that I had done was fabricating new, larger power cables from alt/starter to points. Also completely dissected and 'rebuilt' the spaghetti bundles accompanying the lines to the 14 pin connector. Thermally and mechanically insulated/protected very well. I went through everything related to a complete blackout from the battery to the 14 pin. Went through all my connections at starter and alternator. All seemed well. All of my harnesses were still fresh and nothing VISIBLY awry. Buttoned it all up, but still kept my eyebrow raised.

2 weeks later I'm 6 hours from home in Canada with my son for summer hockey. We just got over the bridge from PEI and I go over a little chicane in the road and it quietly dies again. Now it won't restart. This is now Saturday afternoon. Get towed to 'best' mechanic in town, but don't see him till Monday AM. The fellow who picked us up was the owner/mechanics nephew. We got the car on the lift. The only abnormality I could now see was my thick insulated line from alternator to starter had jumped the heat shield. It was still protected and not making contact, but it was not where I designed it to be. I couldn't make out anything else, and if I did, nephew wouldn't let me work on it.
Anyway, Monday AM I direct the fellow to the line and behold a little further forward (out of line of sight) the line's insulation/protection was burned through by contact/friction with the engine up front. You couldn't see it. Only after we took the line out could it be seen. This essentially shorted out the cars power in when this line was in contact with the block.

Anyway I know I am long winded but like Stan mentioned a few posts back, by the symptoms you describe, you have a fault in a major power line which is intermittently contacting ground and killing ALL electricity. Like I did, I would examine/detach/inspect the major lines from battery, starter, and alternator. Somewhere one of these is electrically contacting a grounding item/structure.

Bill Ball

Stan I looked at the ABS wire and connection today. Seemed fine. Note that the ABS warning did not occur when the car lost battery power. And this is the first and only time the ABS warning has popped up. Most ABS failures are due to bad wheel sensor wiring. Still I will recheck.

Maine, your problem was a little different in that your car died. This one keeps running on the alternator and even sometimes "fixes" itself while driving (the battery comes back into the circuit and the voltage fluctuations stop), so may be in a different part of the harness, but still somewhere in the front engine harness. That's what Alan suggests in post 24. I need to go over this again. I saw nothing wrong on first examination. Too bad I sold my lift. Have to change my avatar.

FredR

Bill,

If you have not been able to fix this one by now I reckon it is time to call in "The ghostbusters".

Don't you just love these cars!

Fred

SeanR

Bill, I encountered something similar on my car over the past few months and replacing the front engine harness and isolating the battery positive cable cured it. The positive cable had a small tear on the insulation and was shorting to the chassis. My front engine harness was completely shot.

Alan

Bill's note above (#5) suggests an Open Circuit somewhere is much more likley than a short to ground - since with a short to ground - while there was no power (/reduced power) - there would be a huge battery current flowing. That there were no sparks at the ground post says this wasn't the case. Battery performance would be hugely impacted, recovery on its own seems unlikley - the kind of current you get with a battery direct short is like welding (it IS welding) tends not to reset very well...

At this point if it were my car - for reassurance I'd just change out the ground strap, main battery feeder to starter, alternator to starter, alternator to jump post and engine block to chassis ground. Basically everything that is critical to power maintenance & integrity all the way to the Jump Post.

Not cheap - but neither is repeated detective work and possibly towing - and the inconvenience of a car that can't be relied on.

If you wanted to go in stages - Battery ground strap and then engine JP - Alt - starter would be my first picks.

Alan