battery cable (+) replacement

MikeB · 12-26-2001, 04:53 PM

For those who have tracked my starter problem, I finally found the culprit. Load tested new battery and tested rebuilt starter/solenoid; both OK. Jumped solenoid + terminal with known good battery and cables. Voila! Time for new positive cable, although it is hard for me to understand why a hefty cable like that could go bad,unless there is corrosion or a cut that I can't see. Anyway...

Does anyone know the routing of this cable? Car is an 85 coupe.
Both ends of the cable disappear into never-never land pretty quickly...

I want to build the cable beforehand. Anyone know the gauge size and approximate length required? Can I swage the terminals now or should I wait until the cable is threaded through the car? Any other hints? This will be my first time into the innards of the car.

Nothing in Bentley on this stuff... thanks in advance.

yelcab1 · 12-26-2001, 05:00 PM

Not so fast my friend. I would not wish a cable replacement on anyone. With this car, it is a very labor intensive thing to do. And, the cable is not cheap.

So, to make sure it is your cable, I would crawl underneath and measure the voltage at the starter and solenoid while someone else is cranking the switch to see what voltage you are getting.

At the very least, clean the ground connection from the tranny to the body, clean the ground connection from the body to the battery negative post.

See if that helps before you go tearing up your positive cable. As you have noted, that monster does not fail easily. Do not replace it unless you have positive proof that it is the culprit.

Your simple test of jumping the solenoid with a known good cable and battery is not sufficient to deduce that the + cable has failed.

MikeB · 12-26-2001, 05:10 PM

Yelcab 1
Did all of the above. See my previous thread "starter problem." The volts are there, but the amps aren't. You are right about the cable replacement; looks like a lousy job. Hence, the post. Cleaning grounds, replacing starters are cake. Replacing the cable doesn't look easy to me. Please reply if I have missed something else.
Thanks
Mike

john walker's workshop · 06:03 PM

remove the 50 wire from the solenoid and check voltage with the ignition switch in start position. is it less than battery voltage? check corrosion at the 14 pin connector it goes thru in the engine room. there's rarely anything wrong with the positive cable other than at each end connector (corrosion). you could also run another ground cable from the starter bolt to the firewall where the trans strap attaches if you don't think it's grounding properly.

MikeB · 12-26-2001, 06:21 PM

JWW:
Terminal 50 showed 11 volts at start. Bentley calling for minimum of 7.5 volts. Battery 12.5 volts. I don't see a multi pin connector for terminal 50 in my Bentley diagram. Looks to me it is a direct line from ignition switch to the solenoid.
Did I miss something? Car is an 85 coupe. I also wire wheeled the paint under the starter mount nuts and the mating surfaces between the starter and engine; nice and clean.
Thanks
Mike

john walker's workshop · 12-26-2001, 06:37 PM

so you're loosing 1.5 volts somewhere. i bet the starter would work if you got most of it back. the 14 pin connector is under the cover on the left side of the engine room. it's the main harness plug off the engine. the big yellow wire is the 50 wire. check the terminals for corrosion. some folks run the 50 wire to a relay which gets power directly from the battery connection at the solenoid, which gives the solenoid full battery power when you turn the key. old solenoids don't respond as well as new ones to lower voltage. the bentley leaves a lot to be desired.

yelcab1 · 12-26-2001, 07:15 PM

Do you have an alarm system with ignition kill? They normally do that by inserting a relay in between the yellow wire from the ignition switch and the solenoid + terminal. THis is how you lose 1.5V from 12.5 to 11V.

Still, I do not think it is your problem. Since you have already replaced the starter and solenoid, let's assume they are not your problem either. That leaves grounding and wiring.

Inspect carefully the two ends of the + battery cable, make sure they are good, not corroded, or cut some how.

Clean off the ground strap connection points (all of them, including the ones in the engine compartment). Inspect the ground points to see if they are corroded or broken.

If you are able to connect from the starter terminal + to the + winding of the starter and get the starter to turn, then it is not your + cable, it is somewhere in the solenoid circuit or the grounding.

I really do not think it is the + cable unless you can see corrosion at the two ends. It is probably in the grounding someplace. Exhaust all possibilities before you replace your + cable. It is a pain in the butt. It goes from the battery, and immediately dives underneath the trunk carpet, snakes under the gas tank, to inside the tunnel where the shift linkages lives, comes out the other side of the tunnel near the engine through a rubber grommet (a big one) and it looks absolutely a b#$%^ to pull out and replace. And it is about 10 feet.

65-911 · 12-27-2001, 05:28 AM

Mike,
You can get the new battery cable from a decent battery shop, or a wielding supply store.
I replaced the one in my 65 911, but I also have the car mostly taking apart so it was easy compared to what you will go thru. I had most of the stuff out of the tunnel.

I had the shop install the connector for the starter side, then I also soldered it to make sure it was well connected. I also covered the part of the cable that is exposed to the outside with shreink tubing.

I fed it in from the rear part of the car, and installed the Battery terminal once it was installed.

Good luck if you decide to replace it, the hardest part will be getting it thru the tunnel, there are clips inside and on mine there was an inner tube to run it thru part of the way.

Bruce

cds72911 · 12-27-2001, 05:38 AM

Of course, I wouldn't advocate changing it if you don't need to, but if you do and you are looking for an alternative to factory part$, you can condsider this idea - welding cable.

A lot of the guys I know that built rally cars (myself included) relocated the batteries and therefore had to have a longer battery cable. The bulk multi strand welding wire that you can get at farm supply stores, welding stores, etc works really well as a replacement.

Charlie

Early_S_Man · 05:03 PM

There just ISN'T any good reason to replace that piece of double-sheathed copper cable of approximately USA 4 gauge ... except for superstition!

Any problem with that cable will be within 1" of either end of the cable ... cut 1/2" off both ends, strip off the insulation, and replace both battery positive connector and a new lug for the starter ... and you effectively have a NEW cable on your car!!!

RoninLB · 12-27-2001, 07:16 AM

My '77 has a connection in luggage comp. under dash for the yellow wire. A voltage test there while trying to start could be enlightning. This is the place where alarm starter kill sol. gets inserted. Ign. switchs don't last forever

yelcab1 · 12-27-2001, 04:49 PM

Mike

One more thing, if you suspect it is your cable, get someone to crank the key over to start, and measure the fileld voltage across the starter.

If something is wrong with your cable, it will show as a very low voltage across the starter. If you are still getting decent voltage at the field winding after the solenoid has kicked in, then it is not your +cable.