Topic: Charging system FUBAR

[parrothead305]

I have a YJ 1990 with a big malfunction in the charging system. Problem is that the alternator is not charging the batt. I have replaced the Alternator, the battery, the starter relay. I have 12V coming form the Ignition to the Atl. also have the constant 12V going in in the #2 terminal. The output of the ALT reads the same as the Voltage of the Batt. After I start the Jeep the Batt. drops in voltage steady, with the new batt. and the old. I removed the alternator from the car and had it tested and everything check out fine. check every circuit from the jeep to the point of removing every fuse from the car minus the ing. and the fuel pump/ t.b. injector. I tried the light test from the negative pole of the batt. the ground in the engine block and it seems like the is no drain in the system. The only thing that I have done so far that I am not sure about is the 12V (Grey cable) that comes on when the  ignition swith is turns on that is attatch to #1 in the alternator goes to ground with Ohm 0.20 if the switch is off. If any body have any suggestion please let me know because I reach my limit. next thing will be to solve the problem with 50cents of fuel and a match. 

[parrothead305]

Thank you all for all the help 

[Jeffy]

You should give people more then a day to respond. 

If you've replaced everything else and it's still not working then your PCM is screwed.  That controls the alternator.

[Bounty Hunter]

Thank you all for all the help 

Nice attitude, do you behave this way everyplace you're new to?

I read your post, didn't have any idea where to look, so I didn't post.  it happens.

[parrothead305]

It is frustating...

[Jeffy]

It is frustating...

Problem with the older Jeeps is that there aren't .pdf's of the FSM's floating around so it's not so easy to look it up.  Someone else had charging issues with a later model jeep and ended up having to replace their PCM as well.

[parrothead305]

Thank you Jeffy, Problem fixed with new ECU and an added bonus, my fuel pump relay and F.I. relays were bypass about two years ago, after I installed the  new ECU they stated working.

[Jeffy]

Thank you Jeffy, Problem fixed with new ECU and an added bonus, my fuel pump relay and F.I. relays were bypass about two years ago, after I installed the  new ECU they stated working.

Congrats!  Where'd you get your ECM from?  One of the links I posted on the other thread?

[parrothead305]

Back to 0 everything failed again... No charge, I have voltage out of the Alt. but a AMPS. Help what else can it be.

[Jeffy]

Back to 0 everything failed again... No charge, I have voltage out of the Alt. but a AMPS. Help what else can it be.

You replaced the Alt., Battery and the PCM, there isn't much else other then a loose connection.  Or perhaps this PCM has problems too.

[oldjeep]

I can post up an electrical drawing for the 1990 YJ.  The PCM doesn't have anything to do with the regulator on the renix setups

[oldjeep]

Link to the diagram.  Left it pretty big so you can read it.   I'd vote for crappy connection somewhere.
http://www.oldjeep.com/files/90YJ25Elec.jpg

[chardrc]

heres that same diagram from autozone that is a little clearer(no see thought)

http://www.autozone.com/az/cds/en_us/0900823d/80/1f/ec/6b/0900823d801fec6b/repairInfoPages.htm

[Jeffy]

Link to the diagram.  Left it pretty big so you can read it.   I'd vote for crappy connection somewhere.
http://www.oldjeep.com/files/90YJ25Elec.jpg

Hmm, learn something new...  Although since it did work fine when he initially swapped them, I would say connection also.  And at least he fixed some other issues with the new PCM.

[parrothead305]

Ok I just finish swapping the ALT with a new one. Connected all the wires IAW the instruction in the ALT (no by pass or rigs) I have 13V out of the ALT when it meets the BATT drops down to 12.20V when the fan (electric) kicks in goes to 11.90v and very slowly goes back to 12.20 if I take all the loads off from the electrical system and let the engine idle I get 12.50+- If I use the lights, forget about it it keeps droping at a steady rate. What is going on what is regulating the current? Is it the right ALT?

4 new ALT (3 burn out)
2 new BATT
1 Starting relay
1 ECU
2 week of troubleshooting
3 days of miss work
4 times stranded in the road without juice
and countless suggestions from IDIOTS recommending to sell or burn my jeep