Just_exploring

Despite all the snow i was able to swap the alternator out. Everything is working properly now!

The pump has a min pressure of 3 lbs and max of 5 lbs. I'm picking up a new alternator at oreillys tomorrow. The truck needs to run and drive so my fiance can get back and forth to work. Hopefully that will get it on the road until I can go hunting at the salvage yard or convert to a more reliable alt. Thank you all for your help and I'll let you know if the new alternator fixes it!

I hooked the voltometer up to the alternator and it was At 13.20 I put the positive on the feed wire and the negative on the negative battery post.

I had it bench tested at oreilleys and it passed. Is there anyway to test the alternator on the truck while it's running?

¤not running 12.33 ¤running at idle 12.60 ¤running with throttle 13.20 ¤running with lights 12.28 ¤running with lights and throttle 12.21 The belt is brand new and the tension is good. Any ideas?

This is the tester I'm using tells you if it is over or undercharging......

Sorry guys it is a 1978 620. ¤when the truck is at idle with no accessories on it is under charging. ¤when the trucks rpms are raised it is charging and sometimes goes into overcharging. ¤with any accessories on it is under charging even with raised rpms. I'm using a battery/alternator tester as my multimeter is mia. So I don't know the exact voltage.

Yes the battery was replaced with a new one.

Just purchased a 78 620. Truck ran fine charge light was on but dim. Truck broke down on highway and brand new mechanical pump failed. The part store did not have the right pump so I had to install an electric pump. Drove 200 miles and had to jump it every 50 miles or so.I took the battery and alternator to the store and had them tested the alt passed and the battery failed. I put everything back together wired the pump correctly. The charge light is still on. Now the issue I'm having in the alt is not making enough power at idle but if you rev it up it is good will even overcharge. If you use the lights it is not charging enough even while revving. I've cleaned all wiring and fuse block. I'm going to add grounds from battery to body and body to frame. Any thing I should check?