Overcharging 620

[Jabron]

Hey y'all.  So, I've been reading the posts on Ratsun for a few years now, but haven't come up with an answer to this.  Here it goes (and I know, the best answer is "put in an internally regulated alt").....which I PLAN to do!  But in the mean time:

 

The issue:  the 620 wouldn't start one day.  Wouldn't do anything.  Checked the battery, and had burnt a couple cells due to overcharging (was hitting around 17v).

 

Got a new battery and a new regulator.  On starting, new regulator started smoking.  No good.  Got a new alt (rebuilt Hitachi stock) and another new regulator.  Installed both.  Now, still overcharging and the charge light came on (this had not been on before).  Another interesting side effect:  it wouldn't shut off by ignition switch.  Hmmm...how could this be related?

 

After cleaning grounds VERY well, ensuring voltage was consistent at all + contacts (batt, starter, ignition, etc) when not running, I noticed some burning on the harness side of the regulator 6-pin connector.  I decided I would trace all six wires back to a nice non-burnt section, replace the offending wires, and hard-wire the regulator in, just to be sure nothing was shorting out.  In doing so, I found that the black (ground) wire was missing from the harness side of the 6-pin connector.  I thought this was great, as I had obviously found the problem.  Wrong.

 

After all connections were re-wired and checked for continuity, I'm still overcharging.  Adjusted the regulator some (not really sure what the hell I'm doing here), but got the charge down to 14.9v with high beams, heater fan and radio on.  Charge light is still on.  The kicker....it now shuts off with the ignition (strange).

 

THE QUESTION:

A) am I missing anything?  What could possibly still be wrong?

B) is 14.9 going to fry my battery?  I know it's right on the verge of the all-around "bad" 15+volts as noted in previous posts.

 

I'm thinking maybe I should just get a DC converter and bring a toaster oven with me everywhere I go from now on, but I'm hoping for something a little cleaner.  Again, I do plan to go with the internally regulated alt at some point, but would like to get her on the road in the mean time.  Any help is appreciated!

[datzenmike]

Seems to me when someone has an external regulator vehicle and they put an internally regulated alternator on by mistake you can't turn them off. Possibly your old and the new one were internally regulated alternators. Your '77 should definitely be an external regulator type alternator.  

 

The regulator must definitely be well grounded. Make sure there is a good ground from the battery to the body sheet metal also.

[banzai510(hainz)]

make sure you got the right alternator

 

 

DO NOT USE the USA made mechanical volt regs(Neihoff Boxed from Napa). They seem to Overcharge quite EZ. I had 2 and wont buy them again

[scooter]

What hainz said, I had one of those and had all kinds of issues.

 

 

[banzai510(hainz)]

I run a USA made solid state unit. CARQUEST and Autozone sell them. I think its really a Wells/Airtex made unit. they seem OK

[Jabron]

banzai510 and scooter.....that's EXACTLY what I have (from Napa).  What a ripoff!  These things aren't cheap.  I will try a solid state reg and see if that helps.  Thanks for the feedback.

[Jabron]

datzenmike, I definitely have a generator vs. an alternator.  As for the ground, are you suggesting that in addition to grounding to the engine block, a separate ground line from batt to sheet metal?  (I know, that's what it said, but I've not come across this before.....).  Also, the regulator itself is grounded via sheet metal.  

[banzai510(hainz)]

you have a Alternator. You dont have a Generator.

 

the Neihoof brand volt reg are expensive

 

by the volt reg there is a ground wire.  Buy a alt for a 77 as its a external volt reg type.  You most likely have the right one and its the volt reg that is giving issues

[datzenmike]

There should be a ground wire from the negative battery cable over to the external volt regulator mounting screw. Sometimes people take it off to change the regulator and forget to put back. ANY wire from the block to the body is fine and will work also.

[Jabron]

Update:  Replaced the regulator with a solid state reg from Autozone (Wells).  This, sadly, did not fix the problem.  Got a brand new ground cable, and added a line to the regulator mounting screw.  This also did not fix the problem.  I'm going to take it to the electrical guru in town and see what is what.  I'll notify y'all of the results, in the event that anyone has a similar issue in the future.  

[DanielC]

This is a manual for Datsun L-16, and L-18 engines.

http://www.davidcmurphy.com/olddat/data/Service_Manual_Model_L16_&_L18_Series_Engines.pdf

 

About page 135 of the manual. it gets into the charging system.  Datsun (Nissan) voltage regulators are temperature compensated, they put out more voltage when cold.  After a few minutes, the regulator warms up, and the voltage cuts back.

 

There is a chart on page 140 of the manual, if it is 50 degrees when you first start your truck, 14.45 to 15.45 is normal voltage.  The voltage should cut back as the regulator warms up.   It is OK to slightly "overcharge" the battery right after just starting the engine, the battery is actually better off getting more charging current right after the heavy cranking current draws the battery down.

 

I know you have a 1977 620.  It has the L-20-B engine.  You should check with the proper service manual for your truck, but I would be surprised if there was much difference between a 1973 charging system, and a 1977 charging system.

 

By the way, internally regulated alternators are not "better", they are just different.  Your truck is wired for an externally regulated alternator.  There are differences in the wiring, and how the voltage regulator, both internal and external, measures the electrical system voltage.

The biggest reason cars went to internally regulated alternators is it is a less expensive system.  Less time to diagnose, only one part to change.  Helps shop mechanics beat a flat rate.

[datzenmike]

Seems to me when someone has an external regulator vehicle and they put an internally regulated alternator on by mistake you can't turn them off. Possibly your old and the new one were internally regulated alternators. Your '77 should definitely be an external regulator type alternator.  

 

 

 

Need to be sure you have the external voltage regulator alternator. Might be an internal one by mistake. Not saying to buy another saying find out. Take back where you got it and have them check their part numbers. Maybe was in wrong box?

[Jabron]

And......for the win.......Datzenmike!!!!!!    Yep, despite multiple checks on the P/N, it was in fact internally regulated.  Cut out the regulator all together, problem(s) solved.  (Hitachi P/N 213-8130, fyi).  Datzenmike, I apologize if I ever doubted you.  I owe you a beer and 14.4 volts of love if we ever meet!

[datzenmike]

:blush:

[5t341tH]

He's always the man to listen to!

And......for the win.......Datzenmike!!!!!!    Yep, despite multiple checks on the P/N, it was in fact internally regulated.  Cut out the regulator all together, problem(s) solved.  (Hitachi P/N 213-8130, fyi).  Datzenmike, I apologize if I ever doubted you.  I owe you a beer and 14.4 volts of love if we ever meet!

[datzenmike]

You will need to properly convert your wiring. (very easy just join two wires together) Unfortunately this will turn your choke heater relay on permanently and the battery will discharge over a weekend. The easy fix is unplug your choke heater relay and join the Blue choke heater wire on the back of the carb to the Red idle cut solenoid wire right beside it. Did this on both my 710s works perfect.