Tesla UMC_a005: Mobile Connector Voltage Too Low Fix
By the EV Fix Guide editorial team · Updated · How we estimate costs
Quick answer
UMC_a005 means the Tesla Mobile Connector is not getting enough voltage from the wall outlet, or sees the voltage drop during charging. It points to the outlet, its wiring or an extension cord, not to the car. At a Tesla Service Center this typically costs $0 (Car is not at fault). An independent shop charges about $150 - $400 (Electrician: outlet replacement) / $500 - $1,500 (New dedicated circuit), and doing it yourself costs $0 (Testing) — potential savings of Varies. DIY difficulty: easy (10 - 20 Minutes).
Symptoms
- 'Unable to charge with Mobile Connector - Voltage too low / Try a different wall outlet' alert
- Charging stops or never starts on one particular outlet
- Charging works on a different outlet or at a Supercharger
- Plug or outlet feels warm, or the outlet is old or loose
Repair cost: Tesla vs independent shop vs DIY
| Option | Typical cost (USD) |
|---|---|
| Tesla Service Center | $0 (Car is not at fault) |
| Independent shop | $150 - $400 (Electrician: outlet replacement) / $500 - $1,500 (New dedicated circuit) |
| DIY | $0 (Testing) |
| Potential savings | Varies |
Ranges are US estimates compiled from owner reports and shop quotes; prices vary by region, model year and parts availability. Report your price.
Can an independent shop fix it?
This is an electrician job. Common fixes are replacing a worn outlet with a heavy-duty one, tightening loose connections, or running a dedicated circuit. The car itself rarely needs service for this alert.
Get matched with an independent shop →How to fix it yourself (easy, 10 - 20 Minutes)
Test on a different outlet, remove any extension cord, and check whether the outlet gets hot. Outlet and wiring repairs should be done by a licensed electrician.
Tools you need
- A different wall outlet to test with
- Infrared thermometer (optional)
Steps
- Unplug, check that the Mobile Connector adapter is fully seated in the outlet, and plug back in.
- Remove any extension cord or adapter chain; they cause voltage drop and are a fire risk.
- Try a different outlet, ideally on a different circuit. If the car charges, the original outlet or its wiring is the problem.
- Check the original outlet and plug for heat, discoloration or melting. If you see any, stop using it.
- Have an electrician inspect the outlet and wiring. For regular home charging, a dedicated 240V circuit with a quality outlet (or a Wall Connector) is the long-term fix.
- If the alert appears on several outlets in different places, the Mobile Connector itself may be faulty; contact Tesla about a replacement.
Had this fixed? Share what you paid
Owner-reported prices keep these ranges honest. We publish only anonymous averages and email you the results.
Frequently asked questions
How much does it cost to fix a UMC_a005 charging alert on a Tesla?
Tesla Service Center: $0 (Car is not at fault). Independent shop: $150 - $400 (Electrician: outlet replacement) / $500 - $1,500 (New dedicated circuit). DIY: $0 (Testing). Typical savings versus the service center: Varies.
Can I fix a UMC_a005 charging alert myself?
Yes. DIY difficulty is easy and it typically takes 10 - 20 Minutes. Test on a different outlet, remove any extension cord, and check whether the outlet gets hot. Outlet and wiring repairs should be done by a licensed electrician.
Can an independent shop fix a UMC_a005 charging alert instead of Tesla?
Yes. This is an electrician job. Common fixes are replacing a worn outlet with a heavy-duty one, tightening loose connections, or running a dedicated circuit. The car itself rarely needs service for this alert.
Which Tesla models are affected by a UMC_a005 charging alert?
This issue is reported on the Tesla Model 3, Model Y, Model S, Model X and Cybertruck.
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Related guides
- Tesla Phantom Drain: Stop Battery Loss While ParkedIndependent: $0 - $150
- Tesla Not Charging at Home: Melted 14-50 Outlet FixIndependent: $150 - $400
- Tesla Battery Degradation: How to Check Range LossIndependent: $100 - $250
- Tesla PCS_a019 / PCS_a016: AC Charging Limited FixIndependent: $150 - $500
- Tesla CP_a004: Charging Equipment Not Recognized FixIndependent: $250 - $600
- Tesla CP_a046: Charging Communication Lost - FixIndependent: $150 - $600
This guide is for information only. High-voltage components (orange cables) can be lethal — leave them to trained technicians. Not affiliated with Tesla, Inc.