12 si ALT and Alt gauge question

[mmw68]

I need to replace the ATL in my 3FE40, and the PO, used a stock 2F FJ40 ALT on the 3FE bracket (so now it's on the DS). I read thru all the tech post about Delco 12si alternators, and that sound like the best solution.

Question - If I add the 12Si, do I need to replace the dash gauge with a 50amp reading? Or will this work fine with the 30amp...it won't fry it will it?

-Mark

 

[Cruisertime]

You will kill that old 30 amp ammeter and possibly start a fire. Run a 50 amp or higher ammeter or just switch off and get an aftmkt volt gauge.

 

[Coolerman]

Short answer: Yes it will fry the 30 amp gauge IF you pull more than 30 amps through the stock harness/fuse block OR if the battery charging current exceeds 30 amps.

If you attach any high powered accessories directly to the battery, or through a sub fuse panel connected directly to the battery, the amp gauge will not see any current pulled through those circuits and will be safe. If you plan on using a larger battery (more amp/hours) with its higher charge rate, or you frequently let the battery become discharged requiring high initial charge rates, then you probably need to swap to the 50 amp gauge.

Note: The 12SI is available in 56amp, 66amp, 78amp, and 94amp versions. 1F alternators were rated 40 amps and the 2F alternators were rated 55 amps.

You may not need a bigger alternator. Add up everything you plan to run and see if the total exceeds the 2F 55 amp alternator.

 

[Cruisertime]

My "sizzle - POP!! - burny smell" happened with a 78 amp model.....had all lights on, radio, and newly installed electric fan.

 

[grant5127]

Funny.......

I'm running a CS130 (Delco 110 amp) through my 30 amp gauge and creates no problem.......

Kinda pegs far to the + side under a heavy load........

 

[mmw68]

Thanks - Iam trying hard not to let the "Smoke" out of my wiring, once that happens
- things don't work that well. All of my accessories go to a Aux fuse box, and my electric cooling fan is on a a relay to directly to the battery as well. Also my Vintage Air unit is wired to the Aux fuse box also.

I planned on running a Aux gauge in the Radio hole on the dash, but hate not having a gauge in the cluster that is dead. Can I still buy a 50amp from Toyota?

 

[grant5127]

50 amp....

The printed circuit board on the back of the clusters differ between the two.....

You could hit up your buddy for a 50 amp cluster............

Then again the wiring is not the same either........

Check a wiring diagram and you'll notice the 50 amper uses a shunt to calculate amps...... it is doable tho with some wiring mods.........

 

[mmw68]

I was thinking about this a lunch, just as long as I keep a OEM load to the OEM fuse box, and run everything else off the Aux fuse box - like Coolman said, then I should be fine.

Grant , Yeah - I'll hit "My friend up for the 50amp gauge cluster.