Recurrent Power Door Lock System Fuse Blown

The same exact thing is happening with our 2008 Prius right now. The fuse has been replaced twice. Blew again. Now the dealer decided that we needed a whole new fuse box to the tune of approx $900. Blew right away when I stopped on the way home from the dealer. Very frustrating. I don't think they have any idea what to do about it. We would love some advice. Taking it back to dealer again tomorrow so they can "make sure the part was good." Ridiculous!

 

something must be shorted. fuse box sounds like a really bad guess by the technician. tricky part is figuring out where it is shorted. if it blows when only the drivers door is locked/unlocked, i'd want to trace the circuit for that door. if it pops when you unlock the other doors, it could be anywhere in the system. pita...

 

That bad fuse box guess was just complete groping in the dark without any further inspection. I do admit that intermittent shorts like you describe are difficult and a troubleshooter's worst problem. What I would do in your case is to cobble together a resettable circuit breaker that inserted into that 25A fuse position, and watch for when the problem happens. Also, a clamp meter on the circuit breaker would allow for actual measurement of the circuit amperage in action. In fact, I remember seeing just such a rig already made somewhere, not expensive.

There have been several reports here of people having problems with the motors in the door lock mechanism, causing intermittent or loss of operation of the locks. But those motors are quite small so I would not expect them to blow a 25A fuse. Perhaps there is a rub somewhere in the flexible parts of the circuit. That is why watching to see when this happens can be useful. Over bumps? Opening and closing the doors?

 

As other's have said, trouble shooting a short circuit can be a PITA. The way to do it, is to step by step follow the circuit from the beginning to the end. Normally, one would start with disconnecting all loads on the circuit, and then connecting one load at a time. Usually through trial and error the short can be found. It can take a long time, and a lot of labor to properly pinpoint a problem correctly. Changing the fusebox is unwarranted IMO. I would do further diagnostics before I declared that the fusebox was the problem. More than likely a wire is frayed and grounding out or a motor or switch in the lock circuit is overloading or shorting out. It may be something as simple as a connector that has melted. Without checking the circuit thoroughly, the problem may never be fixed properly.

I would seek out a good technician who is skilled at finding shorts before I allowed the stealer to simply change the fusebox. The stealers are well known for simply replacing parts rather than repairing the item that is broken. It is the way they do business.

Ron

 

Hello PriusChatters!

I am also having the same recurrent blown-fuse problem with my 2008 Prius. The symptoms are that neither the key fobs nor the lock/unock-all-doors switch on the driver's arm rest work. (We have to use the physical key to lock or unlock the Prius but it is not needed to start the car ... so the fob is working that respect.) The fob batteries and the 12v battery are all fine -- all replaced in the last year and all test fine.

First replaced the door-lock fuse (No 11) a year ago. Fine for a year. Then then the problem reappeared last week. The dealer replaced the blown fuse and it immediately blew -- but it was very late in the day and they didn't have time to investigate. So I went back this week and when the dealer replaced the fuse still again, it didn't blow this time. They attempted to troubleshoot, but couldn't determine why things were now OK. If I understood what the service rep was describing, they saw this on another Prius and had the car in ten times before they found a wire-chafe issue. But they didn't see that particular thing on my Prius.

So we'll see. I now have fuses on hand and will try to see if I can notice any pattern or trigger. If this issue is just a question of replacing a fuse a year, it's not a big deal. If it is recurrent and persistent, it will be an issue. Has anyone had any luck resolving this?

Thanks much for any comments
Bradley

 

Just blew again ... and I got to thinking that I haven't had issues except in extremely cold weather. The last two winters. Same with the other posters above. This thread was started a year ago in winter. Is that coincidence? Or could there be something to it?
Thanks for any comments,
Bradley

 

The "just blew again" refers to my recurring door lock fuse issue ...

 

My problem turned out to be rodent damage — mice had chewed on wires ...

 

Could you pinpoint where exactly you found the damage? There are numerous threads relating to rodent damage, so getting the info on possible access points to plug would be helpful.

 

The mice came in through a common route: through the air vent and cabin filter — we hadn't selected re-circulate air which would have closed a flap. The car sat a month and the mice partied mostly in the dash area. Said fun included chewing on wires that produced the short. Andrew Toyota in Milwaukee did a great job and finding the trouble and repairing the wires.

 

Good news that your dealer could repair the wires individually. Some dealers will replace the entire wiring harness just to repair an isolated spot.

 

Where about was the damage? Passenger side top under the dash or elsewhere? I have the same issues with my #11 fuse blowing

 

It might be faster to just trace down where the problem in your wiring is, using the diagram; it may well not be just where Bradley's was, unless you know you hired the same mice, and they are mice who dislike trying new things.

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