Electrical Gremlins

[dat620_73]

Ok, here's the situation,  I've been using my 73 620 as my daily since my last post. In the last month I've noticed on Mondays (after sitting all weekend) I need to jump the truck to get it started, and don't need to jump it again until the next Monday. I work nights Mon-Fri and figured since I only drive 9 miles round trip a day the battery doesn't get an opportunity to completely recover from the use of lights, radio, amp blah blah blah while driving. So Saturday I only drove the Datsun, about 25 miles running errands. Monday I go to start it, dead. So I check for parasitic draw .07 milliamps (clock/ memory on the radio I figure.) So I connect my power probe and here's were it gets weird. No loads idling at 1000 rpm I get 14.5v, turn on all loads (headlights, blower motor, wipers, radio, hazards, brake lights) voltage recovers to 14.5v, if I rev up to 2000 rpm with loads on voltage drops to 11.8v. WTF!! I have replaced the ballery, and regulator with in the last 6 months. Side note the tach needle is jumpy as well now. I'm figuring it's the alt. but is there something else I'm not seeing?

[banzai510(hainz)]

Loose belt?

 

your battery connections good?corrossion or cracked batt cable  measer ay the battery post not at the cable lug.maybe your loosing it there(corrosion)

 

If still BAD then your Alternator cant deliver a good load.

 

I went with a stock Power Select from RockAuto in my 521.it is made in China but its new and I have 2yrs on it. They kinda expensive but I haven't had to swap themout every 9 months like I did before. Only as its pretty much a perfect fit. sometimes you might have to get a smaller or bigger belt by 5mm.but I have a stash. of 7345 upt o 7360(partnumbers)

 

 

on the patristic draw I use a Test light. if it lights up its drawing to much.  about 45 sec into the vid on using a test light

 

 

I use a Innova battery cheacker in the cig lighter socket so I can monitor this while I drive.so you catch this right away

Buy a version of this

https://www.amazon.com/Equus-3721-Battery-Charging-Monitor/dp/B000EVWDU0?&camp=212361&creative=391349&linkCode=waf&tag=online0a-20

Edited November 8, 2019 by banzai510(hainz)

[dat620_73]

Thanks for reading my novel! I replaced the battery cables when I replaced the battery. I'll try the test light thing. I'll have to make one though I threw mine away when I got the power probe. The belt is tight almost too tight in my opinion, the previous owner "upgraded" the radiator and the lower hose runs dangerously close to the alternator fan. I was going to get a smaller belt if I pull the trigger on the alternator. Update.  Did the test light draw test. It will for 1 second barely light up a regular 194 then go out. but it will light a 194 led. I know led needs very little voltage. 

Edited November 8, 2019 by dat620_73
Update

[banzai510(hainz)]

I just use a Chinese 3 $ test light. I don't know about LED as they don't draw anything.

As for the clock and radion I don't know if that is a lot to make the test light come on. Maybe you could disconnect this.

But if you drive home at night using the lights wipers ect. your most like draining the battery.

If you drive during the day and starts fine with no load then start in morning. Its most likely your alternator don't work under a load and not enough to charge the battery. Enough to run the car but not enouff to start as this needs a lot of juice which it cant provide.

 

I had a Z car that did this.

[dat620_73]

Ok so I bought a remand alt from rockauto, it's a Mitsubishi, and the one I took out was a Hitachi. The tag on the new alt said it was interchangeable. I did have to modify the ground from an eyelet to a spade. Now when I start the truck my charge light comes on. I checked voltage at the back of the alt and it's 11.3. If I rev it up it gets to 12.4 and the light stays on. Good thing my tach no longer jumps around. I went to O'Reillys with both alts. My old one failed, and the new one passed, at 14.5. the pulley diameter looks the same on both, the belt is as tight as I can get it. I don't know where to go from here

[banzai510(hainz)]

Well the first one was bad.the mitshibishi could still be bad. Need to load Check it. I ran them also the Mitsubishi.usaully there is 2 ground spots to put the 8mm bolt thu.so don’t get why you need to swap lugs. I had bad Alta from the store. You still have alt light when key to on before you start?

Edited November 11, 2019 by banzai510(hainz)

[dat620_73]

Thanks for your help with this. Yes all 3 lights are on with key on, then I start the truck and the alt/charge light stays on the other 2 go out. There didn't seam to be threads in the hole for the ground eyelet that's why I put on a spade connector. 

[banzai510(hainz)]

Sometimes there is another threaded hole.

 

take the alternator to another place to test. to confirm.  I took to 2 places to confirm as I didn’t believe he did it right. It passed but went else where then they found it bad. Recheck the connections and plug the T connector back in also the volt reg.

if you got a spare volt reg?

Edited November 11, 2019 by banzai510(hainz)

[Crashtd420]

11 hours ago, dat620_73 said:

Thanks for your help with this. Yes all 3 lights are on with key on, then I start the truck and the alt/charge light stays on the other 2 go out. There didn't seam to be threads in the hole for the ground eyelet that's why I put on a spade connector. 

I dont think your charging....

Where is the actual spade connector?

Is it externally mounted to the case or is it coming from the inside?

 

I could be wrong but that might not actually be a grounding terminal....

Try removing the spade and connect it to the case or a mounting bolt and see if it starts to change ....

 

 

 

[dat620_73]

So that was the problem, my dumb ass assumed that spade connector was a ground. I grounded the chassis of the alt and the light went out, and the alt started charging at 14.3v and 12.9 with all loads on. Thanks Crashd420 and banzai510 for the help. I love this forum, you guys are the best!!

[datzenmike]

12.9 is probably idle when the alternator isn't spinning very fast. Curious what it reads with full load and a faster idle.

[Crashtd420]

1 minute ago, dat620_73 said:

So that was the problem, my dumb ass assumed that spade connector was a ground. I grounded the chassis of the alt and the light went out, and the alt started charging at 14.3v and 12.9 with all loads on. Thanks Crashd420 and banzai510 for the help. I love this forum, you guys are the best!!

Dont feel bad.... only reason I know is because I did it too.....

[dat620_73]

18 minutes ago, datzenmike said:

12.9 is probably idle when the alternator isn't spinning very fast. Curious what it reads with full load and a faster idle.

All Loads on: @800rpm 11.9.  @2000rpm 12.2

 I misread the meter not 12.9 it was 11.9.

No loads: @800rpm 13.6.  @2000rpm 14.3

[datzenmike]

12.2 @ 2,000 won't keep a battery charged. You should be able to drive around with lights on high beam, wippers on full and heater on full, and other than a brief stop at a light, it should be charging at close to 14 volts.

[dat620_73]

11 minutes ago, datzenmike said:

12.2 @ 2,000 won't keep a battery charged. You should be able to drive around with lights on high beam, wippers on full and heater on full, and other than a brief stop at a light, it should be charging at close to 14 volts.

Yeah I was excited to get the light off, but still going to be in the same boat. Larger alt? Smaller pulley? Carry a solar panel in the bed to help charge the battery. Just kidding about the solar panels (kinda) any ideas of where to start chasing wires?

[banzai510(hainz)]

Crashed420 for the Win!!!!!!

 

Chasing wires??? for what You have a drain or not.

 

if you can get 13.2voltswhile driving with a load I would say your ok. just get the cig lighter volt meter and you can adjust your load for whats best.  At idle I sometimes getl low reading. I usualyy shit the lights off ofor a couple seconds and see what my volt meter says.Sometimes its a sticking Vort Reg I guess then it goes back up to 14volts

 

I always shut the heater fan off about a mile  or 2 before I get to my parking spot so the battery recharges up a bit.

 

behonest these rebuilds have been done up about 10 times since new Im sure they are getting to the throw away stage. I have a 35amper and run H4s and have no real proplem. But I went with the new alt RockAuto sales.

[dat620_73]

Sounds good I'll order that today, you were on the right track as well. I'll drive it this week and see what happens. Thanks guys.

[Stoffregen Motorsports]

I recently read an article in one of my many magazines I get and it talked about cheap alternators. The metal used in cheap alternators is poor quality and can cause voltage drop issues. I'll see if I can dig up the article and maybe post a link to the online version.

 

If I need an alternator, I either buy the best quality available, or have them rebuilt. Luckily I have a local shop that is well known for their quality of work and if I have a good core, I almost always have them rebuild it instead of buying a new or reman unit. If I don't have a good core, and can't find a good quality reman alternator, I will buy a cheap one and bring it to them to have it gone through with quality components. The shop name is Boyle Future Tech in Auburn, CA, if you're interested.

[dat620_73]

Auburn isn't that far from me, I'm in Modesto. I have the one I pulled out, I'm not going to spend $20 shipping for a $7 core charge. I go to Reno about once a month may I'll drop it off. Thanks.

[datzenmike]

For $7 keep the original for later. Like said you can rebuild it. The Nissan /Hitachi are so good usually the brushes wore out first. Used to be able to buy replacements. I pulled a used set of a spare car alternator that don't fit to get the one in my truck working again.

 

Is it the external voltage regulator?????

[dat620_73]

The voltage regulator is external. I replaced the original one about 5-6 months ago. It was from what I can remember allowing over 15v back to the battery. I tried plugging the old one back it at the beginning of this whole mess, to see if that was the problem. It changed nothing, however two wires came out of the socket on the regulator side so I had it replaced under warranty last night when I had the alts tested.

[Crashtd420]

13 minutes ago, datzenmike said:

Is it the external voltage regulator?????

 

I was gonna ask this too.... 

Best thing I did was change over to an internally regulated altenator....

 

I had similar issues, so I tested my old altenator ( not the oem) and it was fine,  then I wasted money on a new regulator, then a higher output external regulated altenator and always had inconsistent voltage... when I finally did an internal regulated altenator my voltage became more stable..... 

Might be worth it to look into verses replacing the regulator.. 

[dat620_73]

The problem with the internally regulated alt. Is i don't have the room. My alt fan is 3/8" away from the lower rad hose. Previous owner "upgraded" the radiator.

[datzenmike]

The '78 and '79 620 alternators were internally regulated and will fit the earlier engines. There are some simple wiring mods needed to convert and get rid of the external regulator.

[dat620_73]

Key word "simple". I'm sure you have posted a how to. So I'll look into it. I did just plug in my old regulator and went to go turn on loads starting with headlights then wipers, as soon as i turned on wipers the dash lights started flickering and the truck died.put new regulator back in Went to restart it, and nothing no click no power to anything ( like the batt is disconnected) checked fuses ok, disconnected the battery and reconnected still nothing. Unplugged and replugged the lead going to the starter solenoid (cause why not) and the lights came back on. Old reg is now in the trash pheww.