Alternator low output?. Idle with choke only. IGN Problem?

[wimberosa]

1979 FJ40 alternator with internal regulator

I've been diagnosing issues with only being able to idle with the choke partially out. At first I thought (vacuum leak because I'd re-smog'd during this frame-off) but I've smoke tested it and could only find leaks on the air intake side (at the throttle rod) which would just be sucking air past the air filter which is seemingly ok. I also used the wd40 pee tube test at the carb base and no rpm changes. So I don't think its vacuum.

Now to test the alternator. Here are the details:

12.05 volts at battery not running
11.80 volts at battery with it running
11.79 volts at battery terminal on alternator with it running

Initial diagnosis... Unexpected death of alternator which was previously ok when I was running before this refresh 7 years ago.

So then I just unhooked the alternator from the battery so I wouldn't get the battery volts co-mingled with the alternator volts if alternator was outputing any volts.

0.67 volts at alternator with engine rev'ing
0.45 volts at alternator with engine unrev'd

Seems very low to me ... but alternator is doing "something". Ideas?

A couple of pics of how I have alternator hooked up and how I tested it with it completely unhooked.

 

[brian]

less then 12volts at the battery while running, means the alt is not charging/outputting anything.

 

[wimberosa]

less then 12volts at the battery while running, means the alt is not charging/outputting anything.

Take a look at that second part diagnosis above. It is putting out 0.45 to 0.67 volts at alternator. That seems really low ... but it is doing "something". I guess alternators can just become "weak" and not total fail?

 

[brian]

if they produce 13.5+ volts when working properly.......i would call producing 0.5 of a volt while running...not producing anything.
The 2F fsm covers the charging system and checks nicely.

 

[wimberosa]

Ah....so its not "additive" to the volts measured at the battery. I'm perhaps thinking more like amps (flow) instead of volts (force). So the alternator really should be producing 13.5+ volts by "itself". Yep. FSM is great. Thats actually how I set about doing the test pictured in the photo. When you test like that I get the 11.79 volts...but really thats just reading the battery volts in this case because the alternator is producing so low. Thus I unhooked from the battery just to see what the alternator alone would read.

Anyway....it's dead jim.

Looks like this is a two prong green connector with only one of the terminals being used. Will go look at the faq but if anyone got config like this and recommends an alternative to this AC Delco 19134592 alternator...suggestions appreciated.

 

[Gotta40]

Batt should be 12.6 volts by itself. takes at least 12.8-13.6 volts to actually charge.

 

[charliemeyer007]

I like 14.4 to charge. Volt meters can vary some in readings.

 

[FJ40Jim]

When the engine fuse is blown, there is no power to the ICS and alternator IG terminal.
Symptoms will be no idle and no charging.

HTH

 

[igotta40]

Wow that sure looks clean!

 

[wimberosa]

When the engine fuse is blown, there is no power to the ICS and alternator IG terminal.
Symptoms will be no idle and no charging.

HTH

Hold on! Thats new data for me and in retrospect very very interesting. MY FUSE IS NOT BLOWN but I'm wondering if
I have some kind of continuity problem in that black/yellow wire tied to my IGN on alternator. I ALSO notice the black/yellow
is tied into my carb cooler in the electrical diagram. The other day while I was testing this I noticed my CARB COOLER WAS RUNNING
AT THE SAME TIME THE ENGINE WAS RUNNING. Is that a plausibly normal thing?

I didn't think much of it because I never had a working carb cooler and attempted to fix some missing
bits of the cooler during this frame-off.

So correct me if i'm wrong here but if that IGN on the alternator isn't tied correctly into my key switch (on) then a perfectly
good alternator may still not produce a correct 14+v charge when its turning?

 

[wimberosa]

Seems to me (given the carb cooler is incorrectly running when the motor is running and hot) that its confused about
the switch position. If the carb cooler is confused then the alternator IGN (which is on the same blk/yellow circuit) can
also be confused. So my current bet is the alternator IGN isn't getting the right "on" signal and thus not producing volts
even though the alternator is turning.