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73 datsun 620 l20b not charging battery in need of help


Kadaj

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Hey guys new to the forum, as well as new to the datsun industry. I have a 73 620 with l20b, got it 2 weeks ago love the truck. When I purchased the truck I got home it was an hour drive car ran fine went to start it the next morning car was dying so typically I check the battery and it was low push started it for the next 2 days so I could purchase a new battery. Got a new battery car was fine and drove fine no problems. A week and 4 days later went to fill up on gas then went to start the truck and back to a low battery then as I started driving my fuel gauge lights signals all were out got home thought it's gotta be the alternator tested it with the negative disconnection and truck died had the original alternator rebuilt and replaced the voltage regulator thinking this was the problem now I'm back to a system that isn't charging I need help guys I checked the grounds all are fine had to add one from battery to frame. Fuses are fine no stereo don't know what's going on thanks for any info much appreciated!

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Stop replacing things. Usually the replacement isn't as good as the part replaced and there was nothing wrong with it. It gets both expensive and you run the real risk of a faulty new part being thrown into the mix.

 

Get a good $5 test lamp.

 

Half the fuses are hot at all times. They should be hot on both sides of the fuse. Touch the clips that hold the fuses, not the fuse. Do you have this?????

 

Turn ignition ON. The other half of the fuse box should now be hot. Check both sides of all these fuse clips too. Are they OK???

 

If the fuse box appears dirty/corroded, unplug it and remove the fuses and soak over night in a mixture of vinegar and lemon juice with salt. Rinse and dry in the morning and install.

 

50% of all electrical problems are in the fuses and or the fuse box.

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First thoughts, loose fuse,connections,burnt out ign light bulb,maybe even the wrong replacement voltage reg.

 

Ur best to start a notebook regaurding build date/model yr(not the same thing) also to keep track of upgraded parts and alternative sources for parts.

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Turn ignition on.... this is the bulb test. Light should go out when charging. If bulb does not light the plug in the back of the alternator may be loose or the regulator (maybe not grounded)

 

You say regulator rebuilt? If it was replaced by the rebuilder there were internally regulated alternators that do not use the external regulators. These will not work on a 'pre '78 620.

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Ok sorry for late reply. I did run a test light on the fuse box the clips, they have current on both sides with truck on the regulator I just replaced it with aftermarket, I still have original. the alternator I had rebuilt. For the second step regarding the back of alternator plug are you saying to run a test light on the t plug? Thanks again for the help guys

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Dont buy the Napa made in UDSA mechanical volt regs they suck.

 

How about just put a volt meter on the batter and se what the voltage is.

 

test when reved up then test at idle. then test with lights on and wehen reved up.

 

Maybe it works during the day not loading it down ,then at night you draining the battery where its not chargin. I had this happen once. Just was a weak alternator.

 get a Innove 3721 battery checker from Amazon plug in cig lighter. then youll know.

 

 

dont do the negaitive cabel removed ck. It will not work if you have the accessioers ON(lights ect....).  Might work with everything off.  I KNOW!!!!!!

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  • 2 weeks later...

I just joined this forum with my 74 620, I was searching around and I have same issue. New Alt, Bat, VR and just rewired all to factory diagram. No charging above 12.2 at all.

Upgraded the Alt to 60a Ext reg. alt. Solid state VR with no adjustment. Now I am puzzled.

 

12.2 w/o lights

11.8 w/lights

11.5 w/ everything on

Rev up changes

Disconnect battery and vehicle still operates

 

Starts right up no problems, but its only a matter of time. Can we continue here or should I create new thread?

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If it was working before with the 35 amp alternator but all you did was switch to a 60 amp alternator.take it back and have it tested or replaced if bad.

 

What year 60 amp alternator did you get?

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Ok, sorry for taking so long. Ok well I'm an idiot. I didn't have the belt tight enough. But, when I tightened up the belt it caused the water pump bearings to go out. Well It's all replaced and works great if you like your volts up in the 15 range. Now I'm down to fixing the short in the rear harness and the temp sensor.

 

I bought the VR from eBay from vintage imports. It is a NOS from 1980.

The Alternator is from an early 280z if I'm not mistaken.

 

Thanks guys for the input.

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