Car Keeps Killing Alternators.

Hi All, 

Hoping someone can help here. 

I've recently finished my 2GR swap. On the way down to Sydney the alternator died. I got a replacement and drove back to Brisbane
When I went to leave work yesterday, my alternator had once again died.

This is two in 3000kms~. Whilst they are both used, they worked with no problems until I started the car up on both occasions and suddenly was not charging. Another thing I noticed was that the battery gauge indicated less charge at idle but higher when on the motorway. It's not an accurate indication of voltage but it was enough to make a movement on the dash.

I am not necessarily looking for 2GR specific advice, any sort of input relating to what could cause this would be appreciated.

We have tested the three wires that go to the plug on the alternator. they all receive battery voltage. The light on the dash was working when we replaced the alternator. 

I'm at a loss to what it could be. I doubt it would be heat as other mr2 owners with this swap have had no problems so far. 

Any feedback is welcomed. 

Cheers,

-Eric

Reddtarga
Battery OK?

Yes battery is ok and only 2 weeks old.

Has it failed in the same way this time - i.e. is the charge warning light no longer showing again?
 
Also what else has been spliced spliced into the 3x wires going to the alternator (what else is being supplied from the Alt sensing and Volt Gauage / Warning light fuses)?

What was actually wrong with the alternators? The two that stopped working. Maybe get them inspected to see what the actual failure was? Could be an integrated regulator, internal diode, brushes, bearings etc
Do you have good grounding from the engine to frame and battery to the frame?

Have a read of this webpage from about 1/2 way down where it talks about diode failure and also tests to perform.
http://www.aa1car.com/library/charging_checks.htm
 
Might help you locate the issue.
 

There is a misprint in the mr2 wiring manual I have here that mislabeled 2 of the wires , it is corrected later in the book but you have to be vigilante to pick it up, could that be the issue?

Update: I found out the alternator that the wreckers sold me was a RAV4 one, which is ECU controlled. They told me at the time that "this will work with your engine"

I'm going to have both alternators inspected and test to find out what caused the issue and if it was due to ECU control being present on both alternators but not used.

Craig (Scope) has suggested some scenarios which could have caused the issued:
1. Resistance in wiring or not enough grounding wires.
2. Dirty signal coming into the alternator which is spiking and blowing the reg.
3. Some ECU controlled alternators have the ability to go into "shutdown" mode when there is an issue with the signal coming into the alternator. This can be disabled by removing all power to the alternator and leaving it to sit for a while.

Worst case scenario I will be retro fitting a much simpler alternator but I would rather retain the standard one
 

I'm curious.
 
Is it possible to run the MR2 Alternator off the 2GR engine and have the good ol' solenoid control still working, or does the 2GR computer insist on regulating the voltage itself?