: Charging Problem?

07-08-09, 02:21 PM
I replaced my Alternator in my 84 Deville about a year ago. Now the other day the Service Now light cam on and after the car was shut the battery seemed like it was very low. So I had the alternator tested while it was in the car and it was like 12.XX volts. So he said he would give me a new one. I get there with it out and it tests good on the machine. So i tried a new belt and tightened it. Still not charging. Would a fuse throw off the charging system?

07-08-09, 07:23 PM
Most common problem with a rear wheel drive 4100 is with a loose smog pump belt. This belt if loose, will cause the alternator belt to slip above idle and eventually discharge the battery. To verify, try to rotate the alt. pulley by hand, ENGINE OFF! if you can rotate it, look down while it moves and you will see the smog belt slipping on the water pump pulley. Thats why, I think, it tests weak in the car and normal bench tested. I would say a third of these cars still running have a loose smog pump belt because nobody checks tension and the smog pump is a bugger to get to, to tighten and/or replace its belt. If it were a fuse or wiring, you would have a code and a battery light on. You telling us the service light came on but not telling us what code is present does nothing to help diagnose.

07-10-09, 02:03 PM
Thanks once again, i would have not checked that.

01-03-11, 06:40 PM
I am having charging problems to, but on my 4100 there are two belts. one for alternator and one for the s-pump, so I know it not the belts. I have new alternato and new battery and still the alt will not the charges the battery back up and when tested it is showing low voltage come from the alt. (I have changed the alt 3 times now so I can rule that out and the battery test good to.

01-05-11, 09:22 AM
Please re read my post. The alternator belt only wraps around the water pump pulley so if the smog pump belt is loose, then the alternator belt will slip.