Cheburashka
Active Member
Just had this happen on my 2016.5 75D.
How hard is it to get to the junction box for the fuse and the ptc heater?
How hard is it to get to the junction box for the fuse and the ptc heater?
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Model S Cabin Heater Stopped Working
- Thread starter Snowstorm
- Start date
I heard a pop and shortly …no heat. Happened to have a dozen hand warmers in the car. Read that they absorb moisture, so I put them in the windshield and drove a few hundred miles in below freezing temperatures. I am definitely adding this fuse to the car’s winter safety kit…as soon as I figure out what and where it is on my ‘17 75D.
Service center doesn’t stock heater cores so I figured I’d get another fuse and see if I can get by for a bit. They gave me this…
Anybody think that is right?
Service center doesn’t stock heater cores so I figured I’d get another fuse and see if I can get by for a bit. They gave me this…
Anybody think that is right?
Cheburashka
Active Member
What is that?
This is the correct fuse: Tesla Model S Fuse FWP-40A14Fa FWP-40A14F 40Amps 700V for DC - DC converter | eBay
This is the correct fuse: Tesla Model S Fuse FWP-40A14Fa FWP-40A14F 40Amps 700V for DC - DC converter | eBay
Yeah, I was expecting something that looked more like that. But I thought maybe they changed to a newer fuse after the 2016.5 refresh. Cheburashka - Sounds like you should know as you just replaced it. I assume that is in the frunk area after teardown. Any advice on videos to watch? Anyone know the Tesla part number for the FWP-40A14Fa?
No. Anyone know? What runs on 40a that isn't in the High Voltage group?
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vcor
Tech Specialist
Clever temporary solution with the hand warmers!
That's a 12v fuse. You need a fuse rated for 700v and it's not easily accessible like the 12v fuses. You need to be careful when working around 400v as it can be lethal. I applaud those that fixed it via DIY, but I'd be happy to let the Tesla techs handle this one. The downside is for the oldest cars, Tesla service replaces the DC-DC inverter when it may only need the internal fuse replaced.
Cheburashka
Active Member
Haven't gotten to it yet. Planning to get to it soon-ish though and take some pics. Haven't really been driving much as our streets have been blocked by landslides, downed wires, floods, etc. Just waiting for the weather to improve a little so I can do the job in the sunlight with the garage door open.
Cheburashka
Active Member
I don't think it's that dangerous.
Do shutdown, remove the 12V battery lead + firemans loop beside it. It will isolate and de-energize the FJB completely. Literally no way for power to flow into it.
Gtech
Active Member
Air compressor, condensor fans
Aways 100% safe when 12V removed and fireman's loop without any doubt? I wouldn't bet my own life on it. Contactors can weld etc. so I would advise always to measure to make sure you are at below 10V before touching any bare HV wires. It takes literally a few minutes to measure with relatively simple equipment.
Did some research for you.
2017 MS*D appears to have a front HV distribution junction box and a separate 12V DCDC comverter (Gen1 is combined into 1 unit). The junction box feeds HV to front motor, cabin heater, AC, coolant heater, and 12V DCDC converter. Fuses are inside the junction box. Here is an ebay listing of this junction box with PN 1059891-00-C
Front High Voltage Junction Distribution Box 1059891-00-C Tesla Model S 2017 | eBay
Here is Weber auto's overview on the HV cabling and components for dual motor MS showing the exact same shape junction box as this ebay listing. Fuses are inside. The professor explains HV battery must be removed to get to this junction box (I don't know if this is true, read below). He shows 4x fuse inside including the 40A 700V fuses inside. Presumably one is for the cabin heater. 2nd link rewinds video back and see how the HV cable comes from back of the car (HV battery ->rapid splitter->front junction box) Have to watch a bit to see the full connection path but thats how its wired up.
So if the professor is correct that HV battery must be removed to get to the front junction block, then its defn not DIY. However, the professor is wheel chair bound so I'm wondering if he wasn't able to crawl in after frunk disassembly and get at this junction box. MX front junction box is similar design (but different PN) and accessible after frunk disassembly.
Tesla Service Manual shows no picture but shows a PN of the junction box as 1028843-01-C and no reference to 1059891-00-C. ebay shows 1028843-01-C look like this. Its different shape than the 2017 shown above and most listing I've seen notes 12-16 models.
2012 2013 2014 2015 2016 Tesla Model S Front Distribution HV Junction Box OEM | eBay
Here is a Model X fuse change DIY video. The HV front junction is different PN ( 1049678-00-H ) than dual motor MS. However, MX design is similar to MS dual motors (front HV distribution junction box -> all the HV clients) so perhaps there is hope to get to this junction box on your MS70D
Here is Tesla's parts catalog for MX (2015-2021) MS*D should be very similar. Part #2 is front HV distribution junction box. Part #1 is the DCDC converter (coolant cooled, has 2 bus cables that are likely the 12V+ and ground connection)
Hope this helps. It seems Tesla has changed the front junction box design between 16-17 for dual motors MS but no mentioning in their parts listing online.
One final note. HV voltage is deadly so make sure you are comfortable and knowledgeable with 12V disconnect and HV disconnect (first responder disconnect which basically prevents the HV battery contactors from closing and output HV voltage) and wait some period for any residual dischage to safely work on this system. Please only attempt this if you know what all this means for own safety.
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vcor
Tech Specialist
Here are more details on the fuses and fuse locations for the DC-DC converter and the front HV junction box: Fuses and Current Protection – TeslaTap (for 2012-2016 cars).
KArnold
Active Member
That's how I understand Tesla does it anyway - they specifically said they had to drop the HV battery to reach the fuses on my '17 MS. That's where I stopped considering this a DIY project.
But, I've heard rumors as I recall (maybe previously here) that it might be technically possible to reach it without dropping the HV - but it wasn't something I wanted to try. Think I posted my Tesla repair invoice earlier here.
Tesla service manual says remove HV battery. Hard to tell from their diagram where is located (HV harness from rear of car in left of the pic so probably along the driver side frame rails. Read up on removing Front Junction Box (FJB) to front motor's short HV cable which also requires dropping HV battery pack and disconnect steering shaft (doesn't say anything about LHD vs RHD cars so I'll assume its LHD) This suggest the FBJ is indeed tucked between the HV battery bump in the front and the driver side frame. Cover to open FBJ is facing the wall its mounted on. So it looks pretty buried and perhaps the reason for requiring HV battery removal. Don't know if possible to get it out in that region post frunk disassembly in dual motor cars. Can't find any pics of 17+ FJB mounted on the car for reference.
For dual motor up to 2016, looks like much more accessible
Attempting to Repair Front Collision Salvaged Tesla
Are you contactors opening on their own under a 12v charged battery? They are closing. Opened by default and won't close unless car thinks that there is no HV problem of any sort. Every rebuilder dreams about that sound of closing contactors -)
teslamotorsclub.com
What might is interesting is why gen1 DCDC/FJB combo moved behind passenger fender liner to bulk head behind frunk to then relocate FJB to driver side. Maybe trying to escape water ingress? Study the windshield cowl next time the 3 frunk trim plastic piece is removed. Take a look at the 1.5" hole for the passenger wiper spindle and where water goes entering that hole. Anyway, this whole FJB/DCDC design is highly reliant on the internal moisture seals inside the HV connectors themselves. My guess is thats why we are seeing so many front end HV device failures. I'm garage parked and watching weather forecast before driving these days haha.
FYI, windshield cowl design and all the water runoff design remained unchanged through 2021 according to Tesla parts diagram. Wheel liner got updated in 2015 presumably to close off a softball sized hole spraying water inwards.
Cheburashka
Active Member
Gtech
Active Member
Replacing a fuse is doable on a 2nd gen dual motor FJB but to remove/replacing the whole FJB I don't know if that is possible without removing the HV battery
That seems to be the magic question. By Friday I will have access to both fuses, but I’m not setup to drop the HV pack.
Also, my service center’s fuse shows up in this post, I assume that is the high voltage junction box.
Gtech
Active Member
Your SIBA fuse or FWP fuse are both fine, sometimes Tesla start using other brands bc of cost reduction
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