Gary Knox

I'm posting this, hoping my experience may help someone PREVENT this from happening.

I was away from home for a month, and during that time I had a battery tender connected to the + post in the engine bay on my '89 S4 manual with ~130K miles on the odometer.

I disconnected the battery tender after returning home, and a few days later, started the car and moved it for the first time. After it had been running ~ 4-5 minutes, I saw smoke rising from the crack between the hood and the fender on the right side of the engine bay. IMMEDIATELY turned off the ignition switch and opened the hood. There was a lot of smoke coming from the 14 pin connector and the large wire bundle connected to it that heads toward the firewall (then comes back to the front of the engine).

Since my friend Earl Gillstrom is much more knowledgable about these cars electronics than I am, he came to help "unravel" what had happened and to manage it's repair.

It turns out that about 1/4 of the black molex plastic part that holds all the male pins in place was melted, 3 or the smaller wires were burned/melted, and the solder melted/disconnected at a couple of those male pins.

In analyzing what had apparently happened, we concluded that there was an excessive amount of resistance (corrosion) in some of the male to female pin connections within the 14 pin connector. That resistance had caused significant heat, leading to the melting of the black connector, and the heat transfer through the solder/wires to the first 1" or so of the wiring harness. The connection may not have been separated and re-connected for about 4 years.

SO - a new wiring harness had to be installed, as this one was probably unrepairable. We installed the "new/used" wiring harness that we had on hand.

In reassembly, we thoroughly cleaned ALL the male and female pins in the connector, and used Corrosion Block on all of them (both sides) when re-connecting. The engine started immediately and ran well after the re-assembly was complete. I have since driven the car about 800 miles - to, from, and about 220 miles on the track at Watkins Glen last week. No issues whatsoever - and I checked the "touch temperature" of the connectors frequently - always cold.

I have observed two slight differences since this work was done in the instrument panel gauges. The voltage reads about 0.2 higher than it had before and the oil pressure is about 0.5 bar higher than before. These indicate to me that the current flow to these two gauges (at least) is better than it was previously.

You all might want to check this connection some time and be sure both the male and female pins are clean and free of corrosion.

Gary Knox

PS: The comments about keeping moisture out are great ones. Thanks for adding that.
As Info: This car - for the past 6+ years, and two timing belt changes (28K miles) has always been in the garage, except for about 15 days a year when I'm going to/from or at tracks. There have been 4 trips of 50-200 miles where the car has been driven in the rain over the past 6 years. The hot post cover and plastic "nut" have always been in place.

Before I bought it, the only three owners (New Hyde Park NY, Tulsa OK, and Springdale AR) may or may not have let the car set outside.

SeanR

Great advice Gary, this is one of those things that sort of gets over looked but should be checked out every so often.

AirtekHVAC

Sorry for the problems Gary, but thanks for the info. Still being a newb...14-pin connector maintenance was one of the first things I was made aware of.....I had looked into re-making a better connector, but settled for cleaning and reassembly...

Mrmerlin

Thats a Good synopsis Gary,
I would add, make sure you have a hot post cover fitted to keep out water,
I also take a piece of bike inner tube about 8 in long and 3 in wide and drape it over the connector then fit the hot post cover, put a hole in the rubber to fit over the hot post.
the draped rubber will add to the water resistance of the connector

jeff spahn

I rebuilt my connector last year but I will take it apart and put corrosion block on the connectors and clean them up. I'd love to have as much free electron flow as possible in this car.

mickster

Sorry-made me think of this scene:

Strat_928

Had a similar problem with my 83 while diagnosing starting issues. Turns out I had to replace both top and bottom pieces of the 14 pin connector, refit/resolder the male, female connections as needed and eventually pulled the whole harness, fixing bad spots in that as well. Has run like a top for over a year now. I also did something similiar as suggested by MrMerlin in that I took a piece of rubber hose to put on the post to keep moisture out and keep the plastic cover on tighter.

Good time to remind everyone, do not overlook this very important area of the electrics on the car! It can be a hassle, but better than letting it go too long.

Lizard928

I would add that the problem wasn't 100% caused by the 14 pin connector. As more and more time goes on I see more and more harnesses that have the shielding on the wires intact, but the wire under the shielding is completely corroded.
As most of the electricity travels on the outside edge of the wire this increases resistance and heat. The #1 wire that I see this on is the large yellow pin 14 which is the starter activation. I would suspect the problem to have started while cranking, igniting nearby plastic or oil residue it would take a little soldering before it burst into an actual fire.

If I see any problems on that large wire now I recommend rebuilding the front of engine harness and have all the wires in my shop to do so.

Speedtoys

Lizard928

Oops just checked and that is moreso only with AC. (and possibly ign leads)

michaelathome

I just bought a replacement for mine as well.

Connecters looked ok however they were brittle and cracked upon seperation. Figured that if one connector was that bad they likely all were. Individual wire shielding is shot on the first 1-2 inches on the original harness which is why I tried to seperate it. I am at 89K miles per documents that I have.

Maybe it was an '89 production/material issue? I never witnessed the problem with my '88. I do know that the pin out changed between years, perhaps it had something to do with the amount of voltage passing thru the terminal?

Michael

Bertrand Daoust

Good advice Stan.
Thanks.

dr bob

Gary-

Not doubting the obvious results you experienced, but I'm scratching my head trying to think of any high-current circuits that actually pass through the 14-pin. The 50 circuit between starter relay and the starter solenoid coil is one of the two biggest, but is very low duty time. The other is the AC clutch circuit. Any clue from your forensics which circuit/pin actually caused the problem?

IcemanG17

interesting.....I noticed my racer tends to always show low voltage....whats interesting is my stand alone ECU brain is always 1+ volt higher.....so the gauge shows maybe 12V...but the computer shows 13.4V....car runs great so I believe the ECU since its fresh wires (4 years old)...not 33 like the car

blazing928

and there are a lot more connectors gone as well.....