SeshMurthy

The fusible link on my 2012 is350 blew 3 weeks back. The link that blew was the 150A fusible link for the alternator. I have now tested my alternator. It is working fine. The alternator puts out 14.6V DC and 0.02V AC under load, The didoe reading across from the positive to the negative terminal is infinity one way, and 560 mv (?) the other. I bought a replacement used alternator for $50 and it has identical readings so as far as I can tell it is not the alternator. That leaves the question of what caused the fusible link to blow. Can anyone help me diagnose this.

2013FSport

iTrader: (2)

Most common fault is:
Reversing polarity during battery install.
Diodes in the alternator short.

Rarely does jumping a dead battery w leads reversed kill that.

IIRC the power steering fuse is 80A and generally takes the brunt of it and open before the 120/150A fuse. Any power steering issues? Any work recently done?

SeshMurthy

Thanks for your response.
Here's some additional information
The care has only 30K miles on it and everything else is in mint condition,
No steering or other problems.
The fusible link blew when my wife was reversing out of the garage. The car has not been jumped with the wrong polarity.
The battery puts out 12.2 volts at no load. To me this indicates that all the cells are working fine,
There was some body work done on the car 2 years back. They replaced the driver door that got damaged. They also changed out two fog lights that were damaged and the right wheel well cover.
Is there something I need to check with the existing alternator that I did not.

SeshMurthy

I am at a loss as to what to do.
Here's my current thinking.
1. I traced the circuit out based on the shop manual and as far as I can tell the only thing that can make this 150A fusible link blow is a sustained surge in current between the alternator and the battery and on to the rest of the body. Is this right or wrong
2. Any downstream problems like the steering or the motors that raise the top for the convertible should blow their individual circuits if there is a short. Nothing else has blown
3. There is a possibility that individually these draw a lot of current but that the total current is more than 150 amperes causing the link to blow. I don't understand this, and I need help understanding if this is possible. Right now my first principles reasoning says that this should not happen. My brother who works for Toyota think the same but ...
4. I know my wife did not try to jump the car backwards so that is out as an option.
5. The alternator appears to be OK but could a failure of the diodes be intermittent. This would cause the current to spike sometimes.
6. There was a cold weld in the fusible link. This would constitute a manufacturing defect. Has anyone seen this.

Here's is how I am planning on proceeding
1. Solder the existing fusible link and run the car on idle outside the garage with a fire extinguisher for 30 minutes at idle or till the link blows. ( I know how to quickly disconnect the battery. )
2.If the link blows, iI am replacing the alternator
3. If the link does not blow, run the car on idle outside the garage with all the current hogs on. (lights, fog lights, fan, steering and raising/lowering the top of the convertible.
4. If it blows I'm at least able to reproduce the problem.
5.. If nothing blows replace the fusible link and see if it stays fine.

Please tell me if you think this is not OK.

2013FSport

iTrader: (2)

Can you get a good picture of the blown link?

With what you've put together I'm leaning towards defect as nothing else makes sense. Also, if you can post a picture of the alternator, battery, fuse schematic that would be helpful.

SeshMurthy

I went ahead with my plan. I bought a 140 W weller soldering iron and soldered the fusible link back together. I ran the car for 30 minutes with no problems, Then I ran the car with all kinds of electrical equipment running, Again no problem. So I think it was the fusible link that had a cold solder and it was not the alternator.pr anything else.
I am going to replace the fusible link this weekend and drive the car and hope that it is fine.

Thanks a lot for your help.

2013FSport

iTrader: (2)

Those links are stamped, hard to believe they F'd that up. That said, a solder joint will let you down. Buy something that bolts in. Something solid.

SeshMurthy

I assume the solder will last a few tens of hours. I have bought the original fusbile block link from Lexus (https://parts.lexus.com/p/Lexus_2012...262030170.html) and expect to spend a good 8 hours replacing it this weekend.
If anyone thinks of anything else before then that I should do, I will appreciate any thoughts. I do not want to replace the link twice,

Plesh88

Mine blew when we replaced my alternator and didn't disconnect the battery beforehand. Something as simple as the metal wrench bumping the side and it blew. That thing SUCKS to replace. The amount of force you need because there is absolutely no slack in the wires is insane. I still have this link saved because it was a lifesaver: https://www.clublexus.com/forums/is-...k-removal.html

SeshMurthy

I took a photo of the old fusible link. A wire clearly been soldered to the two plates. There's even insulation on the end of the wire on the wire soldered to the left plate. When I first inspected it, there was a gap between the solder and the plate. I know this is not a smoking gun.

It looks very different from the new one. The new one has a tiny link that seems to have been stamped out of the same metal that the rest of the plate is from. Clear;uy they have stepped away from soldering to stamping out the part to improve reliability and this indicates to me that others have had the problem that I have had.

Btw the car has gone over 10 hours with the new fusible link and nothing has happened,yet. So I am slowly getting convinced that nothing else was wrong and it was the fusible link itself.

Old fusible link with the solder attaching a wire to the two plates.

New fusible link stamped out of single sheet of metal.

2013FSport

iTrader: (2)

I can assure you the OEM component was not soldered.
Are you saying your 'as found link' was soldered? Did I read that wrong?

2013FSport

iTrader: (2)

Adding to the above. It seems likely that a mistake was made by the PO, a hack repair done, and that repair failed as we would expect.
Well, if I read that right.

SeshMurthy

Thanks for helping here. You did read that right. The link when I inspected it after the failure had a wire with a piece of insulation attached to it soldered across the two plates. I assumed that this was the Toyota design. I was surprised when the new part was different.

I have caught someone red-handed. What is a PO?
Not only did they not tell me that they had blown the fusible link, they put in a "hack" repair that used a soldered wire instead of the fusible link and could have resulted in the car catching fire. It has also caused me over 2 months of the car being out of commission ,,,
I wonder what else they have done.

2013FSport

iTrader: (2)

PO is previous owner.

Ya, solder joints are never used that way in a good design. Each time current passes through that type of joint it weakens it a small amount until it disconnects.
It's abrupt disconnect was time and cycle related, vs another failure.

Now if only we knew why it was popped?

SeshMurthy

My wife and I are the only owners of this car. We bought it from Lexus of Greenwich in 2012, then had it serviced by Lexus for the first year and then I did all the oil changes myself. The car was at a body shop for replacing the drivers side door after a hit-and-run accident with a truck on the GWB. The car has 30Kmiles on it and it is in mint condition otherwise.
So it is either Lexus or the body shop.