1992 3FE alternator and charge lamp relay questions (1 Viewer)

[Curtice]

HI all - I am putting this engine into my FJ40, but I am trying to understand how to wire the alternator and I want to include the charge warning lamp on my dash. Below is a snapshot of the charging wiring diagram from the 1992 FSM. Can someone help with the following questions:

1) I thought the 3FE came with either a 80 amp alternator or a 90 amp. However, according to this diagram, the charge warning lamp is wired differently depending on if you have a 90 amp or a 60 amp. A 90 amp does not use a relay (Y-W wire directly to warning light) and a 60 amp does apparently. I am not sure which alternator I have and I want to wire it appropriately. I have attached a couple pictures of my alternator if it helps someone help me identify it. Seems like most of these are 80 amp, but that isn't even an option on the wiring diagram...? My cowl harness with fuse and relay box came from a different vehicle. It has the relay, but that doesn’t necessarily mean my engine/alternator did.

2) If I want to replace the charge light relay with a simple aftermarket generic 4 pin relay, I assume it would still work? Or is there something special about the actual charge light relay (now discontinued) that came with the FJ80?

3) Either way, is the relay necessary at all? Why would it be used with the lower amperage alt only? Seems like it would be used on the higher amp version...

thanks much.

 

[jonheld]

Couple of points:
1991 -early 92 came with an 80 amp alternator with the external fan as pictured above.
early 92-EOL came with a 90 amp alternator with an internal fan.
The 1991 schematic is identical to what you have posted above.
I would assume that there is a typo or simply a carryover from previous years FSMs. The 2F equipped 40/55/60 Series had a 60 amp alternator.

The relay is nothing special as far as I can tell. It will fire when there is a voltage difference between pins 3 and 4, (between battery supply voltage and alternator output voltage).

 

[Curtice]

Awesome thanks Jon. So I’ll go with the fact that I have an 80 amp alternator. I’ll wire the relay and a dash bulb per the schematic.

I figured the 60 amp was wrong. But the following page in the FSM continues with it. So wanted to make sure.

Quick follow up question. I’ve seen people just jump the sense terminal to the IG terminal, rather than run the sense wire all the way back to the battery. Is that appropriate here? Maybe doesn’t matter?

 

[jonheld]

Quick follow up question. I’ve seen people just jump the sense terminal to the IG terminal, rather than run the sense wire all the way back to the battery. Is that appropriate here? Maybe doesn’t matter?

Well, Toyota put the sense wire downstream of the fusible link and the 50 amp AM1 fuse. Personally I wouldn't deviate from that design.

Another thing, if you're increasing the output of the alternator (60 amp to 80 amp) , then you need to correctly size the output cable from the alternator to the battery and also increase the rating of the fusible link.

 

[Curtice]

Great thanks again. I've pulled the alternator output wiring over from the FJ80 along with all the rest of the harness parts I need for the conversion. I think I know how to move forward here. Appreciate the fast help!

 

[Lal00o00]

I’m having issues with my alternator. It charges fine but seems to short (ex: voltage drops when dropping all power windows and charge lights come on) What are symptoms of a bad charge relay? I’ve replaced my alt 3 times now in 3 yrs. Latest issue is my ignition coil keeps getting burned out.

 

[Michael Hanson]

Denso replacement ?