Battery Light On and Low Volts Tested on Meter

[tommytd]

Hello to all the great TD people out there,

My 1985 524td (July 1985 to be exact) is up to it agian. Not to long ago my battery light started coming on faintly and then went fully RED. So I tested the alternator w/ battery connected and car idling and it tested 12.1 volts and eventually it got to low (11.5 volts) to crank starter. I swapped out battery with a new battery, and same thing low voltage while running and the battery would finally get to low to start. So I took out the Bosch Alternator that was in there and got it tested at two places on there machines. Both places told me it was "BAD" or it "FAILED" and was only putting out 12.1v. So I purchased a remanufactured alt. Its a 65 amp alt. (fit perfect). Installed it, started TD and Volts are still at 12.0-12.5 and continue to drop. I brought this "new" alternator to 2 part stores and tested this one on there machines. It tested14.3v and 14.1v "PASS" or "GOOD"

So, what is going on?
I know there are two types to use; a 65amp and an 80amp. Parts store people tell me that I might need the 80 amp Alt? I looked at the 80amp they had and it was too wide in diameter and the bracket on top mount was to fat, it got it the way of the adj. bracket on top mt. so I stuck w/ the 65amp.

Could I have a bad Fuse, Relay, External Volt Regulator or?

Thing that sucks is I sold my original Bosch core to them and dont know if it was a 65amp or a 80amp. Guy told me it was an 80amp cause he ran the numbers and my Bosch came up and it was a 80amp. But my new one isn't a Bosch its a World Wide part number 13150 I believe.

I hope yall reading this can point me in the correct direction on how and where to troubleshoot this and/or chase down the problem,
Thanks!
Thomas

[Fimum Fit]

I once installed an 80 amp in my '86 524td but I had to bend and shim the brackets in various ways and hammer a little extra clearance into the frame, and the two pulleys were still not in perfect alignment, but it worked fine for several years.

If I remember correctly, it was also necessary to be careful in tightening the fuel filter into place to avoid incidental contact.

[Kyle in NO]

Does the alt light go off now? Did you ground the alternator body to the engine block?

[tommytd]

Ok so I grounded the alternator from a casing nut on alternator (nothing was labeled by it, just looked like a good place) and to the ground bar on the side wall next to battery (this is where neg. battery term. bolts to inside panel, and the volts jumped from 12.1 up to 13.9. So now I'm getting juice back to the battery.
There is one problem still that REALLY worries me. My new ground wire gets a little warm after while. it's bolted to the outer case but as I ground the wire to chassis bar theres a little spark at first and as I held it on it got a little warm. 30 seconds later as I pulled off the ground it sparked.
This normal?

[george_jetson]

What gauge wire did you use for your grnd wire? It may be too small for the amount of current.

[Kyle in NO]

You need to ground the alternator to the engine block, not the body.

[Frybrid 524td]

It's a lot easier to run the alternator ground right to the engine block ground point. It's on the driver's side of the block between freeze plugs #3 and #4 IIRC. I also added a ground strap on the passenger side of the block to the fender wall and from the coolant temp sensor housing to the firewall. This solved all erratic gauge cluster issues and allowed the battery to adequately recharge.

[mooseheadm5]

Don't ever cross post like this again. It is a waste of time for people trying to help you. Two of us posted about grounding the alternator in your other thread.

[tommytd]

The first wire I used was a skinny one. I upped it to a thicker size. However, I did mount it to the fender. I'm gonna hopefully find the block mount and move it there. With the alt. Properly grounded the battery charges between 13.9 and 14.1. Very satisfied.
Thanks everyone for the quick replys. None of the parts store clerks knew about the rubber grommets. I never would have thought either.
Sorry about the double post. Won't happen again.