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Charging problems

novox77

1.21 Gigawatts
Nov 25, 2017
1,638
3,544
NH, MA
125' + the length of the charging cord. I'm not electrician, but there is definitely a limit on the length you can run. Maybe one of the more expertise posters can chime in.

I know when I first installed my 14-50 outlet, I used 14' 6-3. Then I later added a 35' RV extension cord. The first couple of times I used it, for some reason, it gave the same error you got. I had to move the amps to 32. But then one day, I decided to see if it would work on 40 amps again, and lo and behold, it did. Never had the issue again. I'm not exactly sure what changed.

125' should still be ok with AWG6 cable. Esp. at only 32A. Look at what the car reads for voltage during the charge. If it's really close to 240V, you're good. If it's under 235V, I'd say you're losing an unacceptable amount of energy (and money) to resistance in the wire.
 
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kcdk99

Member
Dec 22, 2017
19
0
New York, NY
Hey, everyone, I'm having a similar issue, and thought I would tag on here to see if I can get some thoughts and feedback. I have a late 2017 MX 100D with a gen 1 UMC (40 amps). Since my purchase in Dec 2017, I've been charging using my UMC on a NEMA 14-50. It's dedicated run of about 15' of 6/4 to the main panel to a 50 amp breaker.

I've never had any problems getting a full 40 amps until about a month ago when I started to get the "check wiring" error and the light ring on the charge port would never change from dark blue to green. Also, my nightly scheduled charge often fails, and when I can get it to charge, I'm only getting about 23 amps. This has left me in sticky spots a couple times.

I contacted TCS and they ran some diagnostics and couldn't find any issues, and told me that the UMC may be faulty in a way that they can't see via the diagnostics. They also had me try the UMC using the 120v plug, and that had the same communication issue (dark blue charge port ring remains). I tried charging my MX via other AC chargers (J-1772 and Tesla Destination Charger) and it charged at full power as expected. So, I took my MX and UMC to the TSC, and they tried it there on their NEMA-1450, and my UMC worked JUST FINE! So, they decided it wasn't my UMC.

Additionally, right now I have an MX loaner (my MX is at TSC for software updates failing due to bad modules, including the AP module, so fingers crossed it gets replaced with the new FSD module!), and the loaner has a gen 2 UMC... and... I'm having the same issue with this MX and gen 2 UMC. Only getting 32 amps.

So, the sensible conclusion is that something in my wiring is causing the issue. The baffling thing is that nothing has really changed in home (certainly not the wiring), so I can't figure out why it has just now started giving me issues. The only change is a new fridge, but it's a new model with same amperage requirements, so I don't see how that would be causing any issues. And my solar hasn't changed, but I'm charging at night, so that shouldn't be adding any noise to the system. I guess it could be a utility issue outside the house that is throwing spikes, but that's just a guess. So, I guess I'm going to have an electrician check out the wiring to see if they can find any issues... perhaps it's a lose connection or nicked wire.

Thanks for reading my novel. Would appreciate any thoughts or possible solutions!

Cheers
 

murphyS90D

Member
Jul 2, 2016
650
459
Horsham, PA
Check the connections at the 50 amp circuit breaker and at the 14-50 receptacle. If they are loose they will get hot which makes the connection worse which results in more heat. 6 gauge wire is usually stranded. Were ferrules crimped on the ends of the stranded wires? If not one or more strands of the wire may not be clamped by the screw. That also results in heat at the connection.
 

drklain

Active Member
Dec 17, 2016
1,058
1,054
Fairfax, VA/Brussels, BE
You also may have some erosion/pitting in the receptacle itself which is just causing enough of an issue that now it is causing the issue, although the fact the UMC did it with your 120vold normal plug as well would point to the problem being the UMC...but it may be that the receptacle you used for that test as well is the issue.

Try using your UMC (both 14-50 and 120 Volt) somewhere else. Maybe a neighbor's house? You want to eliminate the house or UMC as the issue. If the problem goes away at another location as well (it went away at the Tesla service center) that points to your house being the issue. As you say, it is unlikely the wiring has an issue since you have used it for years. The only wear/tear item is the receptacle (which over time can develop some pitting or fails to connect as solidly due to repeated insertion/removal of the UMC). It is very possible that the whole issue can be corrected by replacing a $20 14-50 receptacle, but you need to confirm whether your problem is the UMC or the house first before you continue diagnosing...
 

ucmndd

Well-Known Member
Mar 10, 2016
6,413
11,966
California
Additionally, right now I have an MX loaner (my MX is at TSC for software updates failing due to bad modules, including the AP module, so fingers crossed it gets replaced with the new FSD module!), and the loaner has a gen 2 UMC... and... I'm having the same issue with this MX and gen 2 UMC. Only getting 32 amps.

Honestly not sure I’m following your story completely, but wanted to point out here that 32A from the Gen 2 UMC is expected best case. It doesn’t get any faster.
 

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