Charging system updates complete!

[gw204]

Well, after about a year of alternator whine and low output I finally got around to fixing the '88. Previously, the charge was fine when I didn't turn anything on but dropped drastically when I flipped on any accessories. Got in the XJ to go to work yesterday and the charge never came up. Pulled into a gas station to check the belt for tightness (I had just replaced that as well). It barely kicked over when I went to start it again so I headed home and got the tools out.

Had been experiencing a varying charge of between 9.5 and 14 V and noticed that the ground cable to the 4.0 was split and cracked badly at the mouting post on the engine. I knew the alternator was dead at this point so I picked up a new 100 amp from Autozone and got two real HD battery cables from Pep Boys, one 32" and one 36" (only down fall is they were both black, no big deal). Picked up the 100 amp fuse from West Marine as well as two 5/16" HD lugs and some adhesive lined heatshrink (red and black). I already had some 4 ga. cable and other lugs at home from when I rewired the boat so I used those. Turn out the lugs I had were 2 gauge and the cable was 4 guage. Rather than heading back up the road I tinned the cable ends, filled the lugs w/ solder and stuck the wire end in. Not the cleanest installation but it works and I covered all the connections in heatshrink. Negative cables got black heatshirk and the positive got red so it's easy to tell what is what. Made the appropriate length cables for battery -> ground, alternator -> main juncion and battery -> main junction.

Pulled the old alternator out and noticed it was completely locked up. I'm not sure if that is from me banging on it with a hammer or not, but who cares at this point! Put the new one in, connected everything up and reinstalled the re-charged battery. It definitely cranked quicker than before and a voltmeter on the battery revealed around 14.6. I turned on every accessory (high beams, flashers, rear defrost, wipers, heater on high, etc.) and the voltage at the battery only dropped to 14.3 at idle.

Cool!!

Just wanted to say thanks to you all for pointing out the site below which was a tremendous help. And many thanks specifically to Craig for taking the time to do the write up!

http://www.olypen.com/craigh/charge.htm

Brian

 

[martin]

Brian,

One more thing you can do is add a bonding strap from the alternator case to the chassis. I found a 24 inch wire is as long as you want, go longer and the current will find another path.

I used a 8 mm bolt to attach the cable to the alternator case - nice of GM to give you a threaded hole! I then attached the other end to the aft hold down bolt for the ingnition coil module.

I wrote Craigh about this and he told me he meant to add this to his article but had not found the time.

With my suggestion you will have 3 paths back to the alternator:
* Chassis-ground strap-block-alternator mount-alternator case
* New battery bonding cable-neg battery cable-block-alternator mount-alternator case
* chassis-bonding wire I suggested- alternator case.

See my running a bonding wire to the alternator case you eliminate the engine block & alternator mount as ground path. In case you have a bad connection between the mount and the block or the block and one of the wires. you still have a good path to the alternator.

I had an electrical engineer tell me it a bonding strap, not a ground strap. It has to do with the potential. Since the alterntor case and the chassis are supose to be both at zero volts then running a wire between them bonds them together electrically.

I agree Craigh has a great article. I also recommend his cooling system maintenance article.

Martin