Pyrotechnic Fuse Blew While Driving...For No Apparent Reason

[scoobybri]

Anyone else have this happen? I was driving and all of a sudden the car starts throwing all kinds of codes, telling me to get to safety. I was simply driving on a country road at 40 mph with the road completely clear of debris. I was able to get to a shoulder but once stopped, the car wouldn't go into gear. It was telling me that it was trying to connect the high voltage system and that acceleration would be reduced (it would not move.) I contacted road side assistance and had to wait 2 hours for a tow. Over those 2 hours, the 12v battery died completely and I could not even put the car into tow mode or the driver's window back up. (Driver's window lowered itself into the door once the battery was dead when I got out.) Car had to be put on sliders to get it on the flat bed since the rear wheels were locked.

Service center is telling me that the Pyrotechnic fuse has blown and will be replaced under warranty. My question is "Why did it blow?" I scared there is a bigger problem under the surface. Car is 100% stock and only 1.5 years old. There's no reason for the main battery fuse to blow unless you have a collision or some sort of debris that breached the high voltage system, neither are the case here. I guess it could be a bad motor or something in the HVAC system but the SC is not saying that these are the reason the main fuse blew. I'm worried about getting stranded again if there is an underlying issue that isn't addressed.

Any insights into this from anyone who has had this issue?

 

[jcanoe]

The pyro fuse could have been defective since the day it was manufactured. In some cases a faulty pyro fuse can shut down the high voltage bus if the fuse detects a false error condition. The only remedy is to replace the faulty pyro fuse.

 

[evrepair]

If the pyroduse blew you wouldn’t be able to drive the car to the shoulder. Did it have power? Or did you just let it coast to the shoulder? (Regenerative braking would have been disabled either way)

 

[scoobybri]

I was able to drift to the shoulder. There was no power, just momentum.

 

[evrepair]

Sounds like a defective pyrofuse or improper installation at the factory (loose bolt). If the new one blows later then you have a bigger problem.

 

[scoobybri]

They replaced the negative contact on on the battery, the pyrofuse, and the 12v battery, all under warranty. Gave me a loaner and the repair was finished the next day. Everything seems to be ok now. Must have been a bad negative connection that caused the fuse to blow.

 

[scoobybri]

Well, 8 days later, the same problem has happened. Car died while driving complaining about the high voltage system disconnecting. Looks like the main pyro fuse blew again. Car was towed to the service center and I'm awaiting a diagnosis. This seems crazy and does not make sense from an engineering point of view, but I was towing empty trailers both times when this happened. (Small 5'x8' trailers.) Two different trailers. The thing is that when I took delivery of the Model Y, the wiring bundle that runs the rear lights and trailer harness was crushed during manufacturing. The left rear brake light did not work on delivery so they had to patch the cable. Six months later, when I used it to tow the first time, the trailer lights did not work. Brought it in and they had to do additional wire patching to fix the trailer light connection. All of these wires are on the 12v system and should only trigger the 12v disconnect "breakers" if there is a short. As far as I know, a short in 12v lighting wiring should not blow the pyrofuse on the main battery. Also, I had successfully towed trailers with the car immediately before the first breakdown and in between the first and second breakdowns. Considering that there were 2 different trailers involved at breakdown, I can't see them being the issue. The fact that the wiring harness for both the rear lights and towing harness was damaged from the factory coupled with the breakdowns happening when towing makes me think something might still be wrong there. But the fact that the main battery fuse is being blown (and nothing in the 12v system which was still working) makes the engineer in me think they can't be related. Who knows, it could be a bad drive motor for all I know. I will post an update when I get a diagnosis from the service center.

 

[jason29252]

Would be very unlikely to be coincidental that the fuses blew both times you were towing trailer and not on any other occasion. There's likely a wiring issues related to the trailer harness causing a short and blowing the fuse. Sounds like a job for tesla to figure out.

 

[scoobybri]

4 business days into diagnosis and the techs at the service center still don't have an answer as to why the car keeps blowing the pyrotechnic fuse. I will keep you posted...

 

[jcanoe]

You should start a log if you have not already done so. You may soon be entitled to invoke the lemon law; i.e., a new vehicle (purchased in Virginia) out of service for more than 30 days in one year or 3 separate attempts to correct the same issue. Tesla would have to buy back or replace your vehicle.

https://www.dmv.virginia.gov/vehicles/lemonlaw.html

 

[scoobybri]

You should start a log if you have not already done so. You may soon be entitled to invoke the lemon law; i.e., a new vehicle (purchased in Virginia) out of service for more than 30 days in one year or 3 separate attempts to correct the same issue. Tesla would have to buy back or replace your vehicle.

https://www.dmv.virginia.gov/vehicles/lemonlaw.html

The car was delivered in November of 2021 so I'm not sure it qualifies as "new" at this point. They've now had the car for 5 business days and there is not a diagnosis of what the problem is. Whoever is handling service center messages said they would get back to me yesterday at end of day. Nothing. I sent another message a few hours ago asking for an update again. Silence at 4:30pm. The lack of communication or of a diagnosis is an issue. If it was an issue of waiting for parts, I would understand but as of tomorrow morning, they will have had my car for a week with no communications other than "tech needs another day" over and over.

 

[scoobybri]

The car was delivered in November of 2021 so I'm not sure it qualifies as "new" at this point. They've now had the car for 5 business days and there is not a diagnosis of what the problem is. Whoever is handling service center messages said they would get back to me yesterday at end of day. Nothing. I sent another message a few hours ago asking for an update again. Silence at 4:30pm. The lack of communication or of a diagnosis is an issue. If it was an issue of waiting for parts, I would understand but as of tomorrow morning, they will have had my car for a week with no communications other than "tech needs another day" over and over.

Just got a message from the service center..."We are doing our due diligence. We are still not sure what the problem is. We need more time." Grrrrr.....

 

[CyberGus]

Maybe your car has pyromania

 

[scoobybri]

Followup just in case someone else had this problem. After having the car for a week, the service center determined that the harness between the battery and high voltage controller was not seated properly. After 1.5 years, I suppose the harness had worked its way loose. When I hit bumpy road (like it was both times the pyrotechnic Fuse blew), there was an arc at the terminal where the harness was not seated properly which blew the fuse. The trailer being attached was a red herring and had nothing to do with the problem, just coincidence. I've driven for 2 weeks now and towed a few times without problems. Fingers are crossed things are fixed.

 

[MilSpec]

Followup just in case someone else had this problem. After having the car for a week, the service center determined that the harness between the battery and high voltage controller was not seated properly. After 1.5 years, I suppose the harness had worked its way loose. When I hit bumpy road (like it was both times the pyrotechnic Fuse blew), there was an arc at the terminal where the harness was not seated properly which blew the fuse. The trailer being attached was a red herring and had nothing to do with the problem, just coincidence. I've driven for 2 weeks now and towed a few times without problems. Fingers are crossed things are fixed.

My 2023 Model X with 3K miles just went through the same issue while driving on the highway. Still awaiting the results, but they are looking at the fuse next. How is your Y doing? I presume no other issues?

 

[scoobybri]

My 2023 Model X with 3K miles just went through the same issue while driving on the highway. Still awaiting the results, but they are looking at the fuse next. How is your Y doing? I presume no other issues?

It's been almost 10 months and I haven't had any problems since...knock on wood. What was the diagnosis on your X?