whats that black thing that bolts onto the alternator?

Ok im trying to figure out why my battery was getting overcharged and then died on me. I thought it was the alternator and still have not ruled it out. looking for breaks in circuits and grounds, etc. but this black box that bolts onto the alternator looks like it is held together with electricial tape. How do i test it, and what is it in case i have to buy another. it's an 93 Cherokee Country with a 4.0 litre. Thanks

Pic?

Your alternator should have three connections - a heavy-gage output lead, and two smaller leads for supplying regulator current.

There should not be a "box" of any sort on the unit. The three connections may be contained in a moulded rubber block (for "convenience",) but that's about it. The regulator is in the PCM, and if there was any sort of "ripple filter" installed, it's usually just a cap - and looks like an ignition condenser (cylinder about 1" long and 1/2" wide, dull silver in colour.)

5-90

Some kind of noise suppressor for the radio?

5-90 said:

Pic?

Your alternator should have three connections - a heavy-gage output lead, and two smaller leads for supplying regulator current.

There should not be a "box" of any sort on the unit. The three connections may be contained in a moulded rubber block (for "convenience",) but that's about it. The regulator is in the PCM, and if there was any sort of "ripple filter" installed, it's usually just a cap - and looks like an ignition condenser (cylinder about 1" long and 1/2" wide, dull silver in colour.)

5-90

Click to expand...

http://i46.photobucket.com/albums/f111/blathan/1071591852_ORIG.jpg
http://i46.photobucket.com/albums/f111/blathan/1071591834_ORIG.jpg
http://i46.photobucket.com/albums/f111/blathan/1071591785_ORIG.jpg

That splans it then

langer1 said:

That splans it then

Click to expand...

so what is it? haynes manual only shows the pos and neg lead. this is not covered in the manual. btw the negative lead is built into this device.

Yep - that's the moulded rubber block, all right!

Those two that come out the long side of the block are the regulator terminals - and they should go on those two screws on your alternator that share a common "shield block" (which merely prevents grounding - it's an insulator.)

Looking at the first picture (since you don't have one of the block in situ,) I'd have to say that the third terminal on the block - with the flexible wire - is the alternator ground proper, and that the output lead is separate in your harness (I've also seen it where the regulator leads and the output lead are moulded into the block, and no case ground.)

So, the "Positive" lead should run to the PDC, the "Negative" lead is a case ground, and should go DIRECTLY to earth (possibly via a splice - but that would be bad design,) and the other two wires you should be able to follow to the SBEC/PCM.

The only thing that looks like it's "held together with electrical tape" is the harness upstream of the moulded block - the tape can be removed, since it just groups the wires. Using tape is a fairly common practise, because it's cheap (I'll usually pull it off and replace it with split loom or spiral wrap - makes it easier to work on the wiring that way...)

5-90

hey everybody thanks for all the help. got the new alternator in and man that was a pain in the butt... everything like the bolts that adjust tension on the power steering pump the bolts that held the alt. on were rusted, however putting it back in was pretty easy. i noticed that there were some corosion on the wire that led from the alt. to the Engine PDC. sanded it off, sanded corrosion off of the battery clamps as well.

Again you all are great and thanks for all of the help.