dr bob

I have a suspicion that I have a failing positive cable. I want to have a new one made, but don't want to pull the old one to measure if I can avoid it. Need to drive to West Marine to get the new one made. So... Anybody know the eye-to-eye length of the positive cable?

TIA!

Tony

How does the cable fail?

he_mech_usmc

In theory, with age and location of where they decided to run the cable at the factory, should something cut or spike the cable casing in anyway, it would allow corrosion to build inside the cable, therefor rendering usable current nil. Thus would be the same if the cable was just plain cut (but not totally) or separated inside the casing which again you would have some form of continuity, however resistance would be high resulting in a "failed" cable.

I apologize for the smart @ssitude, however I have had a long and arduous day of wishing I could be working on my OB instead of actually doing it.

I would check the cable at both ends using a multimeter to check the resistance in the cable, you would also be doing a continuity check at the same time and that should tell you if the cable is "failing". As for length, I'm sorry I don't know.

928er

the problem with the power cables on the 928 is they are an 8 strand copper cable. It isn't the best and I've measured a 1.5 volt drop from one end of the cable to another.

Speedtoys

Sterling:

What would you use then?

928er

I used the 1000 strand high flow cable the car audio guys use...

RFJ

Welding cable is as good as anything.Ray

Speedtoys

Like 1250/30 1/0, assuming it fit.

Glenn M

I have not used these guys but they can make custom cables.

http://www.madelectrical.com/catalog/1-0.shtml

I would also like to get the length.

Speedtoys

When I do this..I'll just get 25', borrow a hammer crimper for the ends from a friend, and cut to length.

danglerb

Sometimes the car guys have a confused sense of what is actually good.

8 strand sounds pretty stiff, I think I would opt for about any marine grade same gauge as OEM, maybe look to a premium jacket type.

The number of strands doesn't relate to how well it carries DC electricity or how much, or how much voltage drop, just how flexible it is and how resistant to damage from movement.

dr bob

Diagnosis has been symptom-centric for the last couple years. Erratically and infrequently, the car has had a low-voltage problem serious enough to cause the dash computer to reset on start-up. Lately it has also been resetting the compute on engine shut-down once in a while. Additional symptoms include low voltage readings on the dash gauge with the car at hot idle speed in 90+ ambient conditions. I've swapped in new batteries, and everything perks up again for a while. Then in a few months, the symptoms would slowly return. I've Ohm'd the cables, cleaned all the connections, replaced the alternator.

Then, a week or so ago I drove to visit a blind friend in the local hospital. Car came up with dim dash lights, no clicks or similar on key to start position. After a few key cycles, suddenly all was as new again. Drove home, and got the low dash lights and computer reset on shutdown. Try a restart and same condition as first try in the hospital parking lot. Without changing anything, I was able to get the car on the lift and start at the battery and work forward to find the voltage drop. Didn't need to go far from the battery box. The voltage at the starter cable stud was between seven and eight volts. At the battery, 12.4 at rest. Verified with an end-to-end check with the voltmeter confirmed that the cable had the drop through it.


Of course, I added the battery charger directly to the battery for a few hours, and all is well again. The high voltage drop in that cable works both ways, so the new alternator wasn't able to push the voltage to the battery properly. Hot day, fans running from the battery end of the cable, the battery was slowly losing ground.

The inflexible factory cable suffers when the motor mounts are holding the engine up where it can move around. A work-around is to cut the original cable back a bit, add a lug to the end, and put a more flexible multi-strand section in where it needs to flex. If the flex section fails it's and easy off-the-shelf piece from a POLAPS to fix it. If I can get a 1- or 2-gauge welding cable to fit in the guide section and the holders, I'll certainly go that route.

dr bob

>> "I need a positive battery cable in black please."

"How long do you want it?"

>> "I plan to buy it, not borrow it!"

MainePorsche

I'm not a pro yet, but I'm trying. I believe it was 1 gauge that I used for a rewiring. It was twice the size of what was replaced.

My alternator output at the post was measured at 13.2 on a good day (with nothing on) with a new heavy Bosch alternator. Pre joining RL I talked to guys in the 928 community that I trust. I came away considering increased resistance in the power wires due to age/degradation. This is what I replaced. Battery voltage at the point was 12.4 - 12.6 as expected. Dissected all the harnesses from alt/starter to the points. No bare wires, but all seemed brittle and aged. The larger wires that pass to the starter in proximity to the exhaust manifold seemed the worst. Lot of work on this job. All insulation was with 2" fiberglass from an aircraft supply house tightly wound. Then tightly wound with silicon tape. This really made the harness thick and not very flexible, but it was workable. Had to order from a local electrical supply house a single terminal that I soldered on to 2 wires for I could not 'stack' the terminals on the alt/starter connections for they where so large.
Before the job 13.2 alt output at the point - would drop to 12.2 with lights, AC with blower on 2, radio. If I opened the roof or a window, I would hold my breath. Now 14.2 - 14.4 - 13.2 to 13.6 with everything on.
Cable degradation is apparently a real issue.

the flyin' scotsman

Could the new cable be made up with one end, alternator, routed under the car in the normal fashion, brought into the battery box, cut to length and the battery connector then secured?