John Speake

Someone sent me this email this morning, I have been trying to help him sort out a problem, which sounded like a temp 2 issue...

""All ok now!!!! Issue was corrosion on terminal 2 wire about 4 inches from the temp 2 sensor (inside the plastic protective casing). There was a small amount of tape on casing but I thought that this was to keep it from cracking as it was getting a little stiff to move. Examination revealled a corrosion "balloon" probably from previous damage,hence the tape on the cover. I followed your advice and again made a careful measurement of temp2 resistances but this time I tested them directly at both the LH and EZK connectors. Again both readings were within a couple of ohms of each other so I thought I would try a loaded circuit test to check the integrity of the wiring. With all 3 connectors removed,I fed 12v into both terminals of temp2 connector from a jump post at the right front corner of the engine compartment. Then with a test light connected to ground,I first touched terminal 19 of the EZK connector...nice bright light...then touched terminal 13 of the LH connector...nothing...voltmeter showed 12v but when test light touched to lead...showedabou t .25v. I was actually relieved that I now had an obvious problem. It seemed reasonable to start looking out front first and suddenly that tape on the harness cover took on a whole new meaning. Anyway,after a proper repair,all is great. Idle is steady and 02 sweep rate is perfect,but the main thing it starts instantly after hot-soak!!! ""

Just goes to show.....

hacker-pschorr

I just finished refurbishing a EuroS harness for my car, IMO cheap insurance if not a bit labor intensive. All new connectors / tabs and new wire sleeve.

I also rebuilt the harness for the starter / alternator. I found the starter trigger wire almost completely frayed with 90% of the wire sleeve disintegrated. It's a miracle my car ever started with this wire (I had no starting issues). Gave me a chance to also remove every wire in my 14 pin connector, clean and update those connections as well.

In the Ferrari world there is a vendor who supplies a kit to replace all of the tabs in every connector with new, kit comes with all necessary tools and boots. Even with cars less than 10 years old they are finding this fixes a lot of annoying and intermittent problems. I can only imagine the condition most 928's are in with regards to the individual connectors.

It would be interesting to do a search for how many 928's were fixed by simply replacing or cleaning a ground connection.

Landseer

Thanks for sharing that, John.


We 928 guys need that kind of electrical connector kit.

I wonder how many cars change hands due to these types of electrical issues. ( I know of two since Friday)

Here's two that drove me nuts, looks like the first might have been stemmed from an earlier fix, but I'm not sure.

John Speake

Thanks for those contributions. It seems that at least a close inspection of wiring harnesses is needed as preventitive mantanance.

I've certainly seen several ring terminals where several wires are crimped together, suffering fron inner corrosion. In theory a good crimp joint should keep air/moisture out but after being in a difficult engine environment for 20+ years, these assumptions break down.....

hacker-pschorr

After all the research I did sourcing my parts, I could attempt to put something together.

To make it easy, a few tools that can run upwards of $50 would be necessary.

I replaced every connector (not just the tabs) because most were so brittle they would not have survived trying to gently take them apart.

the flyin' scotsman

Thats interesting John.

I'll fully inspect the T2 connector and wiring on the S4; perhaps thats part of my issue.

John Speake

I thought it was very smart of the guy to check the wiring while drawing a couple of amps through it.

taffelman

Good info!

My wires are also taped just above the temp II sensor

This will help diagnose my fluctuating warmup phase. Thanks.

Mongo

Great I hope my issue is just as easy to solve.

AO

That temp II sensor can play havoc. My '87 was having no start, erratic idles issuse, and it was all becasue it wasn't grounding well. I've since attached a nominal ground strap to it, and all is fine. But I really like the idea of running some current to verify integrity.

Landseer

Not an application for teflon tape.

fraggle

Hmmmm. Wonde if my excellent powdercoat job is doing the same thing. I'll be adding a ground strap to mine today.

AO

I've received 2 PMs now about this ground strap I did. Here's a pic.

Mongo

Mine isn't powdercoated, but I have corrosion where the bottom grounds to the water jacket. I have been told that this corrosion will have no affect on continuity.

dr bob

Andrew--

You can solder to a copper banjo washer.

There may also be a case for running a tap through the threads under the T2 sensor, and using a star washer under at least one of the water manifold hold-down bolts for a secure ground, cleaning the powder coating off the mating surfaces, etc. Your 'ground' jumper is a great diagnostic but may not be the perfect longer-term fix.

I would think one or two possible Galvanic problems would be avoided completely with a concious effort toward maintaining ground path integrity throughout that whole area.

On the idea of passing more amps through the sensor to identify the extr resisitance, tread lightly. A test lamp can easily draw more current through a thermistor than it was designed to handle. I know it was needed to find the weakest link in the system, but one might do well isolating the sensor itself and passing the current through the wiring directly to ground at engine end, with the test light at the end where the brains have been disconnected. The elements in the thermistor look a lot like a fuse under the right circumstances-- weakest link and all. Don't forget the various permutations of Fig Newton's Third Law of Electrical Reciprocity when testing relatively expensive/inconvenient/fragile elements. The Most Expensive, Hardest to Access, Toughest to Source, Most Important elements in a circuit have a disproportionally higher probability of failure. Multiply that by a consequential damages factor of at least a hundred when you consider tha EZK and LH boxes at the other end of the wires. At least that's what I've found...