If you run 240's long enough, you'll eventually see it all.

I just isolated a particularly nasty problem in a '93 sedan - an intermittent electrical fault. After bunches of futile tests, I finally found that the ungrounded lead from the FI Coolant Temp Sensor is in fact, at times, grounded. I've traced the wiring loom from the computer to the Temp Sensor and as much as I can tell, it does not seem to have been gnawed on by some little critter.

Now, the great things about 240's is that they are so plentiful and similar that if a failure occurs in one, it is bound to have occurred in many others. Before I start butchering the wiring harness, I have to ask anyone else who has had a shorted FI Coolant Temp conductor at what point in its routing did it occur?

Thanks, one and all.

Rich

Could it be a problem with the sensor itself?
--
1966 122s, 1968 142s, 1969 144s, 1979 245dl, 1989 244gl

No. As I said in my original message, I've isolated the problem to an intermittent short to ground in the FI Coolant Temp Sensor conductor between the sensor and the computer.

Rich

Didja ever figure this one out? As a veteran of electrical troubleshooting, I was curious about how, exactly, you determined it was, like you said so strongly, intermittent short to ground within the harness.

You may be fully qualified to say that, but you'd be one of a very few on this board. As for usual causes? There's really only one: someone had something out, and put it back in, pinching the wire. Intake manifold? Heater core? This is rarely a case of rodent damage. You say it is "the ungrounded lead" but that sensor has two. You say it is the one to the computer -- which computer?

Jorrell has you covered on the AC, I'd say. As for the high side port, it is interesting to hear the 93's didn't get one with an R134 fitting. What were they thinking? Hard enough to reach the gauge ports on the compressor with screw-on fittings.
--
Art Benstein near Baltimore

You're getting old when you get the same sensation from a rocking chair that you once got from a roller coaster.

Today is my birthday and last night right after midnight, the god's must have decided to give me a break because I found the short to ground - the conductor was skinned.

I bought this car as a no-start after the original owner had replaced almost anything attached to the engine and given up the battle. I had a sick feeling in the pit of my stomach because I have already reversed some of his wiring expedients in the tailgate and the radio install.

I first thought the Coolant Temp Sensor had gone south because at one point in time it showed 0 resistance to ground at the LH Control Unit connector. Since the Temp Sensor is such a pain-in-the-ass to exchange, I hooked up a test plug to isolate it and checked it on the engine - it read good. So with both ends free, I rung out the conductor to the LH Control Unit which showed that it had gone to ground . . . at first. Then the short cleared itself and I could not resurrect it no matter what I probed or shook.

This led me on a wild goose chase throughout the engine compartment and beyond. Now, every time I checked the FI Temp Sensor circuit, it proved good, but once I buttoned everything up and tried the car, it still idled like a pig.

Knowing how capricious shorts can be and grasping for straws, I decided to spare the Temp Sensor conductor and marry a tough machine tool wire to the outside of the wiring loom, tucking it in at both ends. The taping at the Control Unit end had obviously been previously removed and I thought I would redress it while I was adding the conductor. Just by chance and half-blinded by the glare of a trouble light, as I removed the old tape I saw the glint of some clean copper. A small patch of insulation had been skinned off the conductor. Eyeballing things up, the bared conductor must have been contacting the cable clamp.

I breathed a deep sigh of relief because when I bought the car it had been sitting in a farmyard for a few months and I was worried that some little creature had created a whore's nightmare by snacking on the car's wiring.

Rich

PS - "You may be fully qualified to say that, but you'd be one of a very few on this board."

This puzzles me. I doubt that FEW on this board would not recognize a dead short whenever it rears its ugly head. As far as MY ability to notice a short to ground, let me tell you about the grandest ground fault in my experience.

About 40 years ago (it pains me to say that), I was standing on the decking beside an 8000 HP, 13.2 KV vertical Primary Coolant Pump Motor at Calvert Cliffs Nuclear Power Plant, near Baltimore, getting ready to breathe life into that monster for the first time. As the start-up approached, I heard the rotor hydraulic lift pumps come on. Then, . . . . five, four, three, two, one . . . KA-BLAM! Have you ever been within 50 feet of 13.2 KV going to ground? I thought some joker had set off an M-80 under my hardhat!

When the dust settled, we found one of the HV phases had shorted to ground. I took it personally because I had mother-henned that system from day one and had made a nuisance of myself with the competent craftsmen who had done this ballet many times before. They were bemused, took it in stride and then taught me a lot about the realities of engineering.

While we were regrouping from this catastrophe, I said to the area superintendent in charge of the men working with the tools, "What did I do wrong?" That system had been signal-traced, hy-potted and meggared to within an inch of its life. This flinty veteran of many such battles had mercy on me and said it was probably just the electricians looking for some overtime (double time, at that). He said all it takes to send 13.2 to ground is a straight pin and a pencil line.

I learned one thing that day so long ago - don't screw with the IBEW.

Rico, this has been a long time in coming, but here I go.

"I learned one thing that day so long ago - don't screw with the IBEW."

You shouldn't screw with anyone, and you have. I don't know why, but I'll bet you dealt with those electricians in the same way you replied to me in this post a long time ago. It has been a long time, but I remember the degrading comments very well. If those electricians sabotaged the work, they shouldn't have. However, after your degrading comments they probably couldn't stop themselves....

Another post where you degrade someone is here. That person now happens to be a certified welder who routinely does high purity stainless steel orbital welding, working for a mechanical subcontractor, on site, for the largest computer chip manufacturer in the world. He has also built many bases for fab tools for the same computer chip manufacturer. That chip manufacturer has high standards for welding. I'm certain your welding skills don't begin to compare to his, not even close. No, he doesn't use a welder that came from Sam's Club. The home welding machine then, as now, is an Airco Dip/Stick 160. It is not a cheap unit and uses an inert gas shield.

You've had the nice guy face on for a while, but others need to know the true RicoS.

Maybe you can tell me why you made those unprovoked degrading and offensive posts? With a few exceptions the brickboard RWD section has been free of acrimonious posts.

--
john

Rich,

That story helps a lot. I can guarantee you there are few on this board who will be able to top that experience with power.

And yes, you are right, many can define a short with the context in view -- meaning the relationship between operating current and the unintended path -- sort of like your graphite and straight pin analogy. But the intermittent is generally a tough nut to crack. You actually measured it while it was shorted. Then it disappeared. You related that to what you were doing at the time, I'm sure, but catching it at both ends, so to speak, and knowing it was in the middle, is not a feat all of us can depend on attaining. It bears a few words of explanation.

Because we can't click on your resume, the rest of us have no clue how well qualified your assertions are. At first glance, I thought you dismissed Bud's question a little hastily. I can only go by other statements, such as the niggling discrepancies I noted, which sometimes are just typos, or misstatements, but other times can be clues to misunderstanding. For instance, you say you saw a shiner, but maybe you could warn us where to expect it. What action rubbed off the insulation? Which cable clamp, where? Root cause? Certainly it wasn't caused by an IBEW member, but I've very little experience with multiple PO's -- have been lucky to have mostly professionally maintained second hand cars and not too many zip ties.

I won't make the mistake again, Rich-- being curious about how you've arrived at an assertion. I can take you at your word. Shazzam!

--
Art Benstein near Baltimore

REAL men don't need voltmeters.

Art asked - "What action rubbed off the insulation? Which cable clamp, where? Root cause?"

Art,

I'd have to say all circumstantial evidence points to the PO as the root cause of this calamity. The insulation appeared as if it had been cleanly removed with a knife, no hanging chad, so to speak, and no nicked strands. I just have to think that the fellow either intentionally or inadvertently stripped it away while he was wrestling with the no-start problem. The missing insulation was under the spring metal harness clamp (hanger?) which is clipped to the bracket holding the ignition controller under the glovebox.

Just to give you an idea of how the previous owner approached a repair job, the wires in the tailgate harnesses had, as they always do eventually, separated inside the hinges. His solution: drill holes in the tailgate and the tailgate surround, cut into the harness down in the spare tire well, tag some wires onto the conductors, snake the wires up through the D-pillar and through the new holes into the tailgate, then connect the new wires to the stuff in the tailgate until things sort of work.

There were a number of other things which I've had to return to normal, but all considered, it's a decent car. The body is rust-free, the drivetrain runs out nicely and it doesn't burn or leak a drop of fluid.

By the way, Art, thank you for all the words of wisdom which you so generously share with us here.

Rich









i

OK, I know exactly where now. Those spring clips where the FI relay is meant to go are pretty sharp... But it was the ECU temp sensor lead, not the ICU, right? Oh, yes, you're clear about that, I see on second look.

I suppose the hope you had someone ran into this before would exclude PO tampering, so not much of a lesson for the rest of us to take from your experience. It won't probably help JW in ECT AND THE LH ECU to suggest he look for skinned wires.

Still, I think the best part was your story about Calvert Cliffs. I almost worked at Three Mile Island during its construction a few years before your Maryland job. Almost. Took a different job an hour south of there. I'm sure the one I passed up would have been the more exciting job.
--
Art Benstein near Baltimore

Experience is something you don't get until just after you need it.

I am glad to hear you finally found it. Those shorts are a real pain, expecially when they aren't consistant. Reminds me to remove electrical tape and inspect the wire before 'assuming' anything.

Good luck with getting it road worthy.

--
My name is Klaus and I am a V♂lv♂holic

Amen to that, Klaus. Assume NOTHING!