Someone explain this electrical question

Ok, to start, I have a 74 with a 258.
I was over at my friend's tonight when I was bragging about my inspection sticker for my Jeep. Here in Louisiana, we have to get an anual inspection and a sticker is placed on the lower corner of our windshield. Well, I was worried it wouldn't pass, but it did. I spent yesterday trying to get the wipers to work, and finally, I did. So, I was showing him the wipers and they were not working. Everything else was, but theyt were not. I started to worry the original motor from 74 went out, maybe the brushes were bad, etc...
Then I noticed something hanging from under the jeep. It was my belt. So, I ran to the parts store, bought several belts to have some for backup, installed it, then my wipers started working.
What is the deal. Are the wipers run off the alternator? I always thought they would run off the battery. They ran last night without the jeep running, so I just can't figure it out. It is probably due to the fact that I have a limited knowledge about wipers, but if anyone wants to explain this to educate me, I am all ears.
Tahnks in advance.

 

I have 72 cj5 that I thought was possesed by the devil. Sometimes the wipers worked and sometimes they didn't. Sometimes they would start out working and then just stop, in a heavy rain, while driving a winding mountain road. I thought it was trying to kill me but it was just the wiper switch. It was worn out and since it has been replaced it works just fine. You might want to start there.

 

i had similar probs with my wipers. switch, good ground wire contact, and the linkages from motor to wiper are clean and lubricated good. those are the things i did to get mine going

 

All the suggestions here are great ones! I think what you experienced was a poor/corroded connection somewhere that is making contact but not good contact. Once the alternator starting charging the extra amperage and or voltage was able to overcome this poor connection somewhat to get the motor working. If this is the case then it will get worse and you will need to check all the wiring connections. It could also be the switch as was mentioned, as that would fit into the category of bad connection. It's also possible the motor is getting worn and the extra amperage from the alternator was enough to get it started. An electric motor requires quite a bit to get started but not near as much to keep working. Just a thought.:stout: Nickmil.

 

RainX...

 

I say FORGET the BRAKE TAG!...j/k