Need help 810 won't charge randomly

[afracer]

My 77 810 will randomly not charge. It's very low mile and 99% stock. It was working fine for a while then stopped charging. Figured bad alternator or external regulator. Put on a new 96 amp Dodge Monaco IR alternator and converted the car to the IR internal regulator.  Seemed to work fine for one night then next day voltage dropped from 14 to 11-12 and never recovered, then would start charging again randomly then not. Went thru everything; took both old and new alternators to get tested, both tested good, looked for bad fusible links and continuity checks and cleaned all contacts on  everything and it all checks good. Putting a load on the car (lights) when the alternator is randomly putting out good volts and the volts drop and never recover, even after turning the lights off. Sometimes while it's running and voltage sucks (12-13.5), hooking up the battery charger will result in the alternator starting to charge again on its own and it'll jump up to 14.3 and run great then headlights on or disconnect battery charger and the alternator will stop putting out and voltage drops to 11-12. I'm wondering if it could be the timer unit,  ignition relay, or something randomly big time shorting out. I'm at a loss now and can't figure out anything else, it's so random and barely repeatable. The most repeatable thing is if it's charging fine, turning a load on or letting revs drop to idle while driving and it'll stop charging. HELP PLEASE!

[datzenmike]

What's the build date on the door jam? Trying to find the earliest made 810.

 

 

I had a KA24E alternator on my 710 which originally was externally regulated. Drove it for 3 years worked just fine. Until I put a voltage gauge in. It showed random 14.5 charges but when I shut off to gas up when re started it read 12.6v (no charge) and the battery would slowly go down as I drove. Next time it was shut off an restarted it was fine. Note that it's been doing this for 3 years and I didn't know it.

 

Anyway.... to put a later '86 and up alternator onto an earlier vehicle the two wire plug is totally different so it has to be spliced into the original two wire harness to the alternator. Turns out I got the two wires reversed. Switched them and it now charges all the time. Remember they were backwards for 3 years and no harm.

 

I made a short adapter so it would plug into the stock harness. This is a 100 amp Altima alternator.

 

 

Also I can't believe I didn't see a red charge light when it wasn't charging (that would have tipped me off) so probably that was affected by the wire swap also. Does your red charge light come on? There's a good chance yours is wired backwards too.

[afracer]

Consider it of the earliest build possible for an 810 (#33). The charge light does come on with the ignition, then extinguishes right after start.  I'll go back out and verify the wiring here in a bit, but it was doing the same thing with the old original alternator that just tested good as well.

Edited November 14, 2021 by afracer

[datzenmike]

14 hours ago, afracer said:

 Put on a new 96 amp Dodge Monaco IR alternator and converted the car to the IR internal regulator. 

 

Not familiar with the Dodge alternator nor how that would affect the stock wiring when converting from external to an internally regulated alternator. I assumed this was a Nissan alternator.

 

Was there a two wire plug like in my picture?

 

30 minutes ago, afracer said:

Consider it of the earliest build possible for an 810 (#33). The charge light does come on with the ignition, then extinguishes right after start.  I'll go back out and verify the wiring here in a bit, but it was doing the same thing with the old original alternator that just tested good as well.

 

This doesn't help much. I'm unsure when exactly the 810 began production. August '76???? This would be the beginning of the '77 model year. If this is accurate, then the '77 would be an external regulated alternator as '78 was the advent of internally regulated alternators for ALL Nissan vehicles.

[afracer]

6 hours ago, datzenmike said:

 

Not familiar with the Dodge alternator nor how that would affect the stock wiring when converting from external to an internally regulated alternator. I assumed this was a Nissan alternator.

 

Was there a two wire plug like in my picture?

 

 

This doesn't help much. I'm unsure when exactly the 810 began production. August '76???? This would be the beginning of the '77 model year. If this is accurate, then the '77 would be an external regulated alternator as '78 was the advent of internally regulated alternators for ALL Nissan vehicles.

11/76 production and when I said I just  converted it to an internal regulator I figured that would've told you the car was originally externally regulated. The Dodge alternator is a CS-130 and it has P F L and S terminals on it where only the L and S get hooked up in addition to power and ground.

 

Regardless, it looks like the kid at O'Reilly's screwed the pooch on the alternator test because I tried everything including fooling the alternator and bypassing vehicle wiring in case there was a short with a 158 bulb to simulate the CHG light wired direct from L to the battery and a thick S wire going direct to battery. It produced nothing but 12.5 volts doing this. Additionally when hooking up the L wire voltage with the ignition on would go from 12.5 to 1.3 volts on that terminal so I think it was internally shorted or something. 

 

Bottom line, it looks like it was a brand new BAD alternator. Went and picked up a reman Autozone 280zx alternator and she's now purring like a kitten with 14.09 volts with or without the headlights on. Now I'm thinking either the old external voltage regulator was bad or this bulb check relay that seemed to be shorted internally was bad that caused the original alternator issue. Either way I'm so far up and running after scratching my head and troubleshooting all damn weekend. My lesson relearned is NEVER TRUST THE PARTS STORE KIDS TO PROPERLY TEST AN ALTERNATOR.

[thisismatt]

Yep, can't trust their tests. They will say it's good when only doing 12-13v, but really it needs to out out 13.5+ to charge the battery

[datzenmike]

I don't have very much info on the early 810 is all. Have a '78 FSM, but yes externally regulated caught my attention as I though there were only '78 810s with maybe some 1/2 year '77s. Well that's good to know for sure.

 

 It would have been better to grab something from a wrecking yard that was original. The crap they sell today is beyond belief. The zx has a 50 amp output what was the Dodge? The 810 uses a 60 amp as EFI cars don't like voltage fluctuations.

[afracer]

The CS130 dodge alternator was supposed to put out around 100 amps.  They included a performance sheer that said it put out 117 amps peak

[datzenmike]

I found that the heater fan is like a tornado even idling at a stop. My old stock headlights would flick with the turn signals. My truck was the worst at 35 amps. I put a KA 70 or 80 amp on it.

[afracer]

Happy to report she's been working like a champ. Voltage is 14.2 rock solid.