FJ80 Alternator Concerns (1 Viewer)

[TopGear]

I sure could use some advice! Been reading posts about alternators. Lots of great info, but I might be confusing myself. Here's the problem...

1992 FJ80. At idle, the lights dim, & the heater fan and power windows slow down to a crawl. They are fine when I rev the engine. Reading 12.4v at the battery with engine off, 12.4v at the battery at idle with no accessories on, and 11.8v with hi beams, blower and defog on (still at idle). When I rev the engine, the voltage rises steadily up to a max of 14.8v at 1500rpm's and above. I have no dash warning lights staying on.

Does this sound like possibly the alternator brushes? If so, are the 3FE alternator brushes available in the "holder" (i.e. screw-in) or would I have to solder them in? (My FSM shows solder-in...scary!)
Or could this be the regulator, in which case a reman alt might be the answer?

Thanks for reading!
Mark

 

[cruiserdan]

A fully charged battery should indicate 12.67 volts. Your reading is below that. A battery attached to a running engine should indicate well above that mark. Your readings are indicative of either a sick battery or an alternator that is not "putting out" (so to speak ) Or perhaps an abnormal electrical load.

The cheapest "test" would be to replace the brush package. Also an assesment of the battery age and charge condition should be made. Since the voltage increases with RPM I suspect that the diode-trio and the voltage regulator portions of the alternator are functioning.

D-

 

[nyk438]

My rebuilt alternator does the same thing. Battery is charged fine. Alternator has been doused with mud and it's been fine, better than the original during the FJ80's maiden mud pit voyage.


I also run auxiliary lights 130 watts and they don't dim or anything when the rpms increase. I don't mind I guess it's personal preference.

 

[robbie]

Yes the 3FE alternator is a solder in version of the Nipon denso alt. Not really that bad but if you are squimish then I would not do it. I have rebuilt a few of these and if you take your time and follow the FSM it is not that bad, Patientence is the key to any endevor on mechanical items. If you are in there why not replace the bearings at the same time. You really should be getting higher readings at Idle, either the comuntator is not clean or the voltage regulator is acting up. later robbie

 

[TopGear]

Thanks for the input. It sounds like my battery and alternator may be weak. I think the Interstate battery is about 4 years old, so about due for a new one. The alternator has no obvious labels or tags, and has hand-written "notes" on it....leads me to believe it may have been reworked at some time in the past.

Not sure about soldering in the brushes. I can re and re it, but maybe I can find a local shop to look at the brushes. Will also PM C-Dan about alternator prices.

It's a real drag pulling into Tim Horton's drive thru and having to rev the engine to lower the window (only happens in cold weather).

Mark

 

[Rookie2]

I'd run it in to an auto store and have them put it on a tester. If it's a cold weather thing, I'm going with bad battery.

 

[TopGear]

I swapped batteries with my minivan’s 1 year old Diehard (both group 34). The truck seems to crank a little faster, but I still get low voltage and dim lights at idle. I apparently have the 90 amp alternator (internal fan) which has the easily-replaceable brushes. Think I will tackle that next.

I have one additional symptom that I would like to throw in here:

When cranking the starter, if the truck does not fire right away, I have noticed that, as the starter cranks, it will occasion almost cut or short out, with all lights, fan and radio also cutting out. This will only be a brief “hiccup” (less than a second), and then it continues cranking and starts up. I thought it was the weak battery, but now I swapped batteries and it still happens.

I just replaced my starter contacts a month ago, and am wondering if I screwed things up. The contacts went in well, and cured my “clicking” starter.

Any ideas?

 

[Riley]

Mark - still have the battery tested. They'll do it for free. If your near Langley try All-Start. The owner is a good guy and they rebuild alternators and starters (i think) in addition to selling batteries.

The hiccup sounds like an open in the battery or connections when under load (or bad starter or contacts). I'm out of other ideas.... keep us posted.

 

[cruiserbill]

I have a rebuilt alt and have the same problem. i dont recall the OEM doing this. i have installed a new batery and there is no differance. i wondered if this was normal for an aftermarket rebuild. ????????