electrical??????

[gettinbetterXJ]

The xj is dead again..kinda. Here's what happens, I fire it up and it runs fine for a few minutes down the road, then I slow to a stop sign and it idles way down and tries to die unless I keep the rpms up real high. When I start out again I have to keep the rpms way up there until finally the jeep begins to move forward ever so slowly. On top of all this there is the interesting phenomenon of the radio cutting out when I turn the headlights on, or the radio stays on but the headlights dim real low. I replaced the stock alternator about 11 months ago, then replaced that alternator about 2 months ago. On the current alternator when I take the negative lead off the battery the engine dies immediately which means bad alternator right? What in the jeep could possibly be killing aternators? As far as I know the aternator only outputs and takes no inputs right? With a full charge on the battery (which is also only 2 months old) the jeep will run for a few days or weeks depending on the type of driving I do until this problem rears it's ugly head again. Can anybody shed some light on this for me? I can't keep putting in new alternators every two months or so.
Thanks in advance for all the help!
BILL

 

[kbeckman]

What year, engine?

 

[gettinbetterXJ]

The Jeep is an 88 4.0 I6. However I just replaced the block with a new one last week...Yes, I had this problem prior to the engine swap, I was hoping it would go away with the swap.

 

[kbeckman]

The Alternator is pretty simple on the '88. There is one input, the Yellow wire, which shold have 12V on it only when the engine is running. The Red heavy wire goes through a Fusible link (Blue one) and is attached to the starter relay, and then to the battery. Make sure this the fusible link is still good, and chack the connection on the starter realy. It's best just to take it apart and clean it well, and put it back together.

Do you have a volt meter? You should be able to see when the alternator is charging by looking at the output volatge (Red wire). It should be 13 - 14 Volts when charging. The Tan/White wire goes to the charging indicator.

You should be able to start the engine, and remove all the wires but the red one. Apply 12V to where the yellow wire geos into the alternator, and hear it drop then RPM's slightly as it's charging.

It's either a bad connection someplace, or you've got a bad alternator.

 

[homey_15]

where are you buying your alternators? cheap alternators (oreillys, autozone) are pretty notorious for being incredibly cheap and shitty, definetly would reccomend a quality replacement. although more expensive, it'll be less of a pita in the long run. good luck

 

[gettinbetterXJ]

In taking everythign apart and checking connections I got to pull the battery cables out of the engine compartment and examine them out side of the heat shield they were in, both of them were trashed the insulation literally crumbled off both cables leaving about 8 inches of bare wire. So I replaced both cables and the xj has run fine for going on four days now. With the engine off the battery reads 12.7 volts on my meter. With the engine running it reads about 13.8--14.6. Also I didn't find any kind of fusable link between the starter and the battery, are some not equipped with this or do I need to get one installed?