Third straight charge cord overheating

Third straight charge cord overheating

I bought my Dec. 2018 standard range S about 14 months ago and proceeded to charge on average about 100 miles per day on the charge cord and adapter that came with the car. For 8 months, I didn't have any problem charging it on the Nema 14-50 outlet that I had professionally installed. It consistently charged about 23 to 24 miles until it all of a sudden started giving overheating errors and reduced the charge rate to around 8 to 11 miles per hour. Tesla replaced it, and the same thing happened with the new charge cord and adapter. They replaced it again. This third cord does the same thing with the exception that it will eventually go back up to 23 miles per hour before again dropping back down to about 11 miles per hour.

Is this normal? I don't think the outlet is bad. I have time-of-use billing, and the slower charging speed can sometimes cause it to still be charging when the peak rate starts.

Aerodyne | June 30, 2020

Not normal, and don't overlook the possibility that the outlet is improperly installed.

What voltages are being displayed in the car before and after it drops the current? The lower the voltage, the higher the draw. At some point the MC will detect high heat/ low voltage and cut out.

Also, be advised the Gen 2 is not rated for 32 A. They say it is. But look at the label on the adapter. My 6-50 says 31 A. When I asked Tesla support, they said it was good for 32, but the regulatory body made them put 31A.

I set mine at 28A, cord is still a bit warm, but charges at 20 mi/hr, a good number. Try setting it at 28 A.

NKYTA | June 30, 2020

For the first time in many years my wife plugged in my 14-50 at home, but not solidly the last couple charges, and it didn’t seat well. Only got 19 A, instead of 29 A.

Make sure the plug is well seated!

I have it set for 29 A because pre-covid that is what I can max charge at my office without tripping the breaker, there.

Ohmster | July 1, 2020

@NKYTA. Is the amperage setting not location dependent? I could swear I have it set for 20A at work and 48A at home.

‘17 S75 + ‘17 X75D Both: Uncorked [E]AP MCU1 FSD AP2.5 Intrusion 20.20.1 Grin on!

Anthony J. Parisio | July 1, 2020

If you are not getting 28 to 30 miles / hour something is wrong. I would bet the outlet is faulty and not seating well or not gripping the plug well. Try having the Nema 14-50 replace by a different electrician. I would not trust the last guy to do it right if he got it wrong the first time.

Anthony J. Parisio | July 1, 2020

If you are not getting 28 to 30 miles / hour something is wrong. I would bet the outlet is faulty and not seating well or not gripping the plug well. Try having the Nema 14-50 replace by a different electrician. I would not trust the last guy to do it right if he got it wrong the first time.

barrykmd | July 1, 2020

Anthony J. Parisio | July 1, 2020
If you are not getting 28 to 30 miles / hour something is wrong.

Not necessarily. Both at home and at my ski condo, I am plugged into a 208V line (buildings have commercial space on ground level, so feed is 3 phase). Max charge rate is 24-25 mph. I dial it back to 32A and get 20 mph..

crazy canaler | July 1, 2020

Thanks all.

I look tonight when it charges what voltages are being displayed.

I thought the max charge rate a MS could get from a Nema 14-50 outlet was 24mph, not 28 to 30?

Also, how could it be the outlet if it's fine for 8 months and then starts acting up? The plug has always been very very snug.

Bighorn | July 1, 2020

Are you unplugging it at all? It’s not designed for that—the outlet. 3 failures seems too coincidental to implicate the cord. | July 1, 2020

Ok, I strongly suspect it's the receptacle/wire. If you have aluminum wire, it is almost 99% sure it's the receptacle/wire connection. The reason aluminum wire is a problem and causes fires is the aluminum deforms over time and makes a poor connection. It heats up and is quite risky.

Now aluminum wires can be used safely, but the receptacle has to be rated for aluminum wire. Most 14-50 receptacles are not rated for aluminum wire. You also have to apply a special paste to the connections.

Now if you wires are copper, then it could be just a loose connection. In either case, I would stop using it until it is fixed. The problem is NOT the Tesla cable and this is a real safety concern.

Lastly, I'd also confirm you are using an industrial NEMA 14-50 receptacle. Consumer-grade receptacles are designed for ovens and dryers, where the connection/disconnection is made maybe 2-3 times in the life of the house. Industrial grade are designed for repeated insertions and removals. The cost difference is not all that much.

rxlawdude | July 1, 2020

Agree with all: this is not a UMC fault if three of them behave the same.

NKYTA | July 1, 2020

@Ohmster, not having been to the office for 3 1/2 months, I can neither confirm nor deny. ;-)

But I think you are right.

crazy canaler | July 1, 2020

Ok. I just started charging at 11:48pm. I was getting 21mph 32/32amps and 243v.
At 12:22am it was displaying "Mobile Connector over temperature limit. Maximum charge rate reduced." and I was getting 11mph, 16/16 amps (the amps setting was reduced to 16), and I was getting 245V.

My condo is about 50 years old and did have aluminum wiring running from the meter to the breaker panel but replaced it with copper wiring when I moved in 4 years ago. When installing the outlet, the electrician installed a new breaker, new wiring and new outlet.

I do unplug the cord every day - usually several hours after it's done charging - and it is very snug. Sometimes, I even need to use 2 hands.

I guess I'll call my electrician and have him check everything.

Bighorn | July 1, 2020

Check the temp with an IR thermometer and see what’s getting hot. Or just go by feel.

akikiki | July 1, 2020

crazy canaler, that wear on your contacts of your cable connector or the adapter is eventually going to become loose and affect your charging. Likely to add more heat. If you insist on disconnecting, you might want to put a separate shutoff box and switch upstream of your outlet, so you don't need to unplug the UMC daily.

Anthony J. Parisio | July 2, 2020

Sorry I was assuming 240V not 208V.

slbuchwalter | July 2, 2020

@crazy I had a similar problem with my NEMA 14-50 outlet for several summers in a row. I'm in AZ. The 2014 Model S would stop charging overnight when the nighttime temperatures in the garage stayed above 85F. I suspected it was related to the load on our circuits from A/C turning on and off at night, which only happens in the summer. My electrician thought it might be utility-related, i.e. the line voltage from the grid might be variable at night. I don't seem to have that problem since we got a 2020 Model S last month, though we are using the same NEMA 14-50.

crazy canaler | July 3, 2020

Thanks all for the help!

I called my electrician, and he came out late in the day, took the outlet apart and immediately saw that it was bad but had no idea why. He came back later with a replacement, and now it's working fine.

Also, he agreed with people here that I should leave the cord plugged into the outlet all the time.

@ Bighorn, the grip on the plug was 4 seconds hot (holding it a 5th second would burn you). Now it's not.

Thanks everyone for the help!

By the way, my electrician's wife just got a 3 and loves it, and he is contemplating getting the Cybretruck when he gets rid of his F150 in several years.

Bighorn | July 3, 2020

Awesome that you got to the bottom of your vexing issue and that group thinking got to the correct answer. That’s how I got hooked on the forums—collective diagnostics of a novel product.

NKYTA | July 3, 2020


Anthony J. Parisio | July 3, 2020

Very happy it is solved for you.

SbMD | July 3, 2020

Just saw this, and glad this got fixed, @crazy canaler.

Agree that this Forum has served the owners well for this and other issues. If it wasn't said, this isn't the first time this problem has arisen for other owners and was solved here.

Also good that Tesla was very supportive in replacing your UMC repeatedly.

rickrparker | July 3, 2020

Kind of related. I am in Dallas, travel to Utah and New Mexico to ski. The SuperChargers all get really stiff in the cold. So before plugging in the SC cords, I stretch the cord in a 90+ degree angle before I plug in just to take the tension off the receiver in the car, so as not to let it pull to hard on the plastic. Even on warm/hot days I do it and it seems to make my head feel better if nothing else. Fall into that all important category - Can't hurt, might help.