DIY HVAC Tools

American Standard mini split error code UH

Current sensor fault.

  • TypeFault
  • SystemControl board
  • Can I fix it?Technician job
  • Applies toMitsubishi Electric-built units

What UH means on a American Standard

The outdoor board's compressor current sensor is reading an impossible value.

On this platform, UH is a fault: something has failed or is disconnected and needs diagnosis.

Common causes

  • A failed sensor or board.

How to fix it yourself

Do the reset and the visual checks, but the underlying repair needs a technician with a meter and the service manual.

  1. Reset the system: switch the breaker (or the outdoor disconnect) off, wait a full five minutes so the boards fully discharge, then switch it back on and restart from the remote.

Switch off power at the breaker before opening either unit. Capacitors in the outdoor unit hold a charge for several minutes after power is cut.

When to call a technician

Board-level fault.

Which American Standard units show UH

This page applies to American Standard 4TXK / 4MXW / 4TYK hi-wall inverter and Mitsubishi Electric-built units units on the Mitsubishi Electric-built units. American Standard's own documentation lists UH as "Current sensor fault", the same definition used across the Mitsubishi Electric it is built on. If your unit shows a code with a different shape (for example a four-character code, or a plain number), it is from a different table; use the lookup with your exact code.

Where American Standard shows this code

Mitsubishi Electric-built units: Wall units without a wired controller signal a fault by blinking the operation indicator lamp; the code itself shows on a wired controller (MHK/PAR series) or on the wireless remote after entering its check mode (see your manual). On the outdoor unit, the control board LEDs blink the same code. P codes are indoor-unit faults, E codes are communication faults, F codes are outdoor-unit faults and U codes are outdoor-unit and compressor faults.

Other American Standard codes

Same part of the system as UH:

All American Standard error codes

UH on other brands

The same characters do not always mean the same thing. Check the brand on your unit.

Questions people ask

Can I reset a American Standard UH code myself?

Yes. Turn the system off at the breaker for five minutes, then restart it. If UH comes back, the fault is real and needs the checks above.

Is it safe to keep running a American Standard showing UH?

The unit will usually refuse to run, or run with reduced output, until the fault is cleared. Repeated resets do not fix anything and can mask a problem that is getting worse.

What will a technician check for UH?

Board-level fault. Ask for the measurements, not just a parts quote.

Sources

  • Trane / American Standard Mini Split HW Inverter Service Manual (4TXK / 4MXW), SVM027A-EN, 2024
  • Mitsubishi Electric M-Series service manuals (self-diagnosis tables)

Updated September 2026. Codes and definitions vary by model year. If your manual disagrees with this page, your manual wins. Send a correction.