Strange Alternator Failure…

Image result for bosch alternatorSparky, my 87 924S, had an alternator failure a couple of weeks ago, but it was, without a doubt, one of the strangest alternator failures I have ever experienced.  Not to say that it has never happened to me before – I have lost the belt, had them suddenly stop working, lost the bearings and had them make horrific dying screams, and even had one fall out of the car.  But this one was a new one.

It was Friday afternoon and I was at the Nort Northam Collection when I decided to head home to DeLand, braving the murderous traffic on an under-construction I-4 in Orlando.  However, a stop at the local Trader Joe’s was in order to purchase a package of carrot-cake creme-filled cookie/pastry things (happy pills.)  When I got in the car, I had the key in hand but not in the ignition. The battery light was on.  Key in the ignition, turn it on, and the battery light went off.  Crank up the car, and no battery light.  The car started fine, light was out, all is good.  Out to the interstate to try my luck at not getting killed.

It started raining.  Heavy traffic, construction, and rain.  Oooooo fun.

I like listening to the radio, but the radio kept cutting out.  Then, about three miles into the traffic, the battery light came on.  Bam.  Radio off.  Headlights off.  Let’s find out how far the battery alone will take me.

tzQR+cABTIuAQm5ozRCQggNot that far, but far enough to get out of the construction.

Call home, wife comes to pick me up, I hook up the trailer to the truck, go back and pick up Sparky, and head home.  Rain had stopped by then, traffic had thinned out a bit, so the ride home wasn’t too bad.  Unload at the house, put Sparky to bed in the garage.

Saturday morning.  I charged the battery, started the car and tested the alternator.  Nothing.  The alternator had ceased alternating.  Of course, the local DeLand auto parts houses don’t stock alternators for a 924S, so I went to the headquarters in Orange City and pulled a used alternator off the shelf.  A stop at O’Reilly to check it for function, and back home.  Installed the new unit in an hour or so, cranked up ol’ Sparky and all was good.  Charging at 14.2 volts. I then took Sparky for a test-drive, and that’s when I made a discovery.

Sparky was running a whole lot better.  Idle was smoother.  No change in idle when turning on the air conditioning.  Faster acceleration.

Without making this any longer than it has to be, it seems that Sparky had some knacky wiring left over from the engine fire two years earlier, causing the battery light to glow ever-so-slightly.  Discovering this when I bought him back a few months ago, I bit the bullet and spent the money to acquire new harnesses for the battery-alternator-starter and also for the primary wiring under the hood – all from Ian at 944Online in south Florida.  A bit pricy, but it seemed that the positive terminal connections with the primaries (the three wires on the positive terminal that feed power to the rest of the car) had been getting a bit hot to the point of melting some of the insulation near the terminal.  Replacement was in order so I spent a few hours one weekend doing the job.  As a result, no more glowing battery light and no more hot terminal connections.

in that first month or so, I had also noticed that the idle was a little rough and the car lacked acceleration, even for a 924S.  Checking, the motor mounts were new.  I tried to pay attention to pick up on some clues, think about what had been done and what could be making the engine do what it was – or was not – doing.  But changing the alternator cured both the idle and the acceleration issues.  Why?

A trip to see Richard at S.E.A. Manufacturing in Orange City – the alternator-and-starter guy – revealed the answer.  It seems that the hot wiring was messing with the alternator, and the alternator was well on its way to a heated death when I repaired the wiring.  It seems that the rotor in the alternator “fried” – a technically-correct term.  It is also not repairable.  The failure was related to heat building up from resistance in the knacky wiring which over time was feeding electricity back into the alternator and slowly destroying it.

The old alternator was sucking up electricity, so there was barely enough electricity available to make the engine run.  Thus, when I replaced the alternator coupled with the new wiring, the engine suddenly had a ton more electrons moving around, and it ran better.  Lots better.

So this was a new one.  Lessons learned.

Looking on the internet – which of course is always right – I found that this phenomenon of back feeding into the alternator and ultimately frying it is a real and common thing.  As our cars get older, things tend to wear out, including the insulation on various wiring, connectors and cables.  That said, the insulation on the larger power and ground cables cracks, opening the copper to the air.  If you can see copper through a crack in the insulation, and the copper is actually green, the ability for that cable to carry electricity efficiently has been compromised and that cable needs to be replaced.  Simply taping it up to “seal” the insulation is not enough – the damage has been done.  The so-called “bad ground” may not be a ground connection, but instead may be a bad cable.  Something to keep in mind.

Image result for corroded ground wire

Author: Kevin Duffy, LLC, DeLand, FL

After retiring from a career in Law Enforcement, Kevin Duffy turned his attention to one of his passions, Porsche 944's and 924S's. He owns LLC in DeLand, FL, rescuing and restoring forgotten Porsches, bringing them back to a useful life. He is especially interested in the rare-but-beautiful 924S Special Edition. He can be found at Porsche Club events, including track days, tours and shows, as well as other car-focused events around the southeastern United States.

One thought

  1. Great article……I was just going to mention SEA Manf. in the OC. They are great…..glad you got it sorted.

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