FJ62 Alternator (1 Viewer)

[FJ Silver]

I've got a BC/DC redarc charger that takes care of my house battery. It charges at 25ah.
I find my alternator getting hot around 260 Fahrenheit(could be normal) after 30 min of charging, but its also making noise, kinda like the belt is slipping on the alternator itself.
Voltage is staying normal though between 13.6 and 13.8V.

I just wanna make sure I'm not killing my alternator fast.
Does the FJ80 version for the 3fe have higher output? and is it a straight swap for the FJ62?
Or would you suggest another altenator brand. I'm only charging a 50amp lithium house battery.
Thanks

 

[Seth S]

I'm not following what you are doing between your house and the truck alternator.....but its not abnormal for alternators to generate heat when they are loaded.....that's why most have some sort of cooling fans built into the pulley or shaft. I don't think the Fj80 alternator is much if any higher rated amperage. You need to figure out what your actual electrical load is and then figure out if you need more charging amperage.

 

[FJ Silver]

I'm not following what you are doing between your house and the truck alternator.....but its not abnormal for alternators to generate heat when they are loaded.....that's why most have some sort of cooling fans built into the pulley or shaft. I don't think the Fj80 alternator is much if any higher rated amperage. You need to figure out what your actual electrical load is and then figure out if you need more charging amperage.

Gotcha.
My load (when also charging my house the battery) is 25amps + whatever the 62 is using to run.
There is a DC to DC charger going from my main battery to the house battery, that's my redarc.

I vaguely remember the fj62 alternator putting out something like 55amps max and the FJ80 with the 3fe putting out 80 amps.
If I want to install some additional off road lights etc. I'd be really asking max output from the alternator if its only putting out 50 amps or so.

 

[Seth S]

With a 55 amp alternator you have a max of 792 Watts of power to use and with an 80 amp your max available wattage is 1152 watts. The items in your 62 that use the most power are the fuel pump, blower motor, ignition system, and lights. If you have lots of lights, accessories, big radio/sound system, winch etc then you start to strain the stock alternator.

The best place to start before going crazy with alternators is to replace and upgrade your battery power and ground cables, put in new battery clamps, clean and redo all your ground wires, install a light harness upgrade for the stock headlights. Your truck is old and its wires are old.....old wires are inefficient and burn up a lot of power through internal resistance. ......my 60 with the stock headlight harness loses 1 volt between the battery and the bulb...which is significant.

So in your case your house battery is using somewhere between 325 Watts and 360 watts when its charging. I don't know off hand if the 3FE alternator is different between the 62/80. What you might consider....especially if you are desmogged....is running a new mini denso or similar alternator in place of the smog pump. The second alternator would just be for your house battery and would simply freewheel when it wasnt needed.

 

[Seth S]

Also....is your house battery system completely isolated from the truck battery?

 

[FJ Silver]

Also....is your house battery system completely isolated from the truck battery?

Thank you and yessir that's what the dc to dc charger does, part of it anyway.

Wiring is as clean as it gets... I got rid of the factoring fusing by the battery a long time ago and have fairly new wiring including the alternator wire.
I'm not experiencing any lack of amps or volts. I was more worried about the noise the alternator was starting to produce after charging 25 amps ( I have a shunt installed) for 30 min.
I was able to reproduce the noice as well on a high load v.s. low amp load.

I'm in Utah... often in the middle of nowhere offroading, so that's why i'm considering replacing it with a higher amp new alternator and keeping current as a spare.
I couldn't quite figure out if the stock 3fe alternator is different / better on the 80 series. Which would be the logical upgrade.

 

[Seth S]

Thank you and yessir that's what the dc to dc charger does, part of it anyway.

Wiring is as clean as it gets... I got rid of the factoring fusing by the battery a long time ago and have fairly new wiring including the alternator wire.
I'm not experiencing any lack of amps or volts. I was more worried about the noise the alternator was starting to produce after charging 25 amps ( I have a shunt installed) for 30 min.
I was able to reproduce the noice as well on a high load v.s. low amp load.

I'm in Utah... often in the middle of nowhere offroading, so that's why i'm considering replacing it with a higher amp new alternator and keeping current as a spare.
I couldn't quite figure out if the stock 3fe alternator is different / better on the 80 series. Which would be the logical upgrade.

Sounds good. Alternator noises tend to be from belts slipping or creeping or from bearings that are wearing or failing. Perhaps your bearings are starting to go.

 

[FJ Silver]

Sounds good. Alternator noises tend to be from belts slipping or creeping or from bearings that are wearing or failing. Perhaps your bearings are starting to go.

I just replaced my waterpump and the idler pulley bearings, so everything is nice and quite
Maybe that alt belt is just a little too loose for when I've got full load going.
Would a higher output load create more resistance on the pulley though?

Is the alternator bearing easy to replace? let me check the FSM. At least alternators even OEM are pretty cheap.

 

[Seth S]

I just replaced my waterpump and the idler pulley bearings, so everything is nice and quite
Maybe that alt belt is just a little too loose for when I've got full load going.
Would a higher output load create more resistance on the pulley though?

Is the alternator bearing easy to replace? let me check the FSM. At least alternators even OEM are pretty cheap.

Yes, the higher the load on the alternator.....and the more amperage that the alternator outputs the harder it becomes to turn. If the belt is old or loose it could certainly be slipping on the alternator pulley under periods of high demand.

Replacing the bearings in an alternator isn't often an easy task as they really are not built for ease of assembly. A reman alternator can be had for $50 so its rarely worth that amount of effort.

 

[FJ Silver]

Yes, the higher the load on the alternator.....and the more amperage that the alternator outputs the harder it becomes to turn. If the belt is old or loose it could certainly be slipping on the alternator pulley under periods of high demand.

Replacing the bearings in an alternator isn't often an easy task as they really are not built for ease of assembly. A reman alternator can be had for $50 so its rarely worth that amount of effort.

Thank you Seth, really helpful.
I just replaced the belts together with the water pump, so that's probably it...
I used to over-tighten belts and ruining bearings with that, so maybe I've go that one too loose now.

 

[Spook50]

Yes, the higher the load on the alternator.....and the more amperage that the alternator outputs the harder it becomes to turn. If the belt is old or loose it could certainly be slipping on the alternator pulley under periods of high demand.

Replacing the bearings in an alternator isn't often an easy task as they really are not built for ease of assembly. A reman alternator can be had for $50 so its rarely worth that amount of effort.

To add this this; the bulk of the heat generated in the alternator is the diodes that make up the rectifier. The alternator actually creates 3-phase alternating current which is then rectified to approximately 13.8V DC when operating properly. I have looked into a product called the Quicktifier that's intended to augment the stock rectifier with a much larger one that also has dedicated cooling. This would also take much of the current load off of the stock rectifier and add to the longevity of it. What I was curious about but couldn't get an answer on was if it would also help to avoid voltage dip when at idle. Unfortunately the page to order it doesn't seem to work, and my emails hadn't been returned so I will attempt to build my own at some point and see just how well it could work in practice.