Ductless Communication Issues

Error codes E1 or EL01 on 4-wire Bryant/Midea Ductless units indicate a communication error between the indoor and outdoor units. This simply means that the two units are not talking to one another.

The issue can be caused by the indoor unit, the outdoor unit, or the wire. To identify where the issue is, begin by setting your meter to DC voltage. Place the red lead on L2 or 2 and your black lead on S or 3 in either the indoor or outdoor unit.

The DC voltage should be jumping between 0 and 100 VDC, mostly positive, and switching to negative momentarily. Some digital meters may not show the switch to negative on the display, but they will beep for a split second. This is the normal communication signal.

Identifying an issue with the Outdoor Unit

If the DC voltage is jumping between 0 and 100 and staying positive, this is an indication that the outdoor unit is the issue. Check for proper A/C voltage going to the outdoor unit. Follow the wires from L1 and L2 to the control board in the unit. Check for A/C voltage there. Look for the digital display on Multi-Zone units and LEDs on single-zone units. Check for DC voltage at the capacitors + and – terminals on the back of the IPM (Inverter Power Module) control board if accessible. You should read around 300 VDC. If you have 230 volts of AC going into the IPM Board and no LEDs or DC voltage coming out, the board has most likely failed. If this is the case, check the compressor resistance leg to leg, L1, L2, and L3. All three should be approximately the same on a good compressor. Check each leg to ground. If anything other than OL shows, the compressor is bad and may have taken the IPM out. Replace the compressor and IPM.

Identifying an issue with the Indoor Unit

If the DC voltage is steady around 10 to 20 VDC the problem is the inside unit control board. Check for A/C line voltage at L1 and L2. Is there a condensate pump or condensate safety switch? If so, how is it wired? The safety switch must break only L1. If L2 or 3/S is broken with the safety switch, that may be the cause of the fault. Rewire the switch and check the unit for operation. Even if the unit has operated for a long time, this may be the issue. 

Does the indoor display come on? Turn the mode to fan only. Does the fan come on? If the display or the fan does not come on, this is an indication that the control board in the inside unit may be the problem. Unplug the fan motor and louver motor and try again.

Double check the wiring between L1, L2, and S/3. If they are crossed, that can cause the E1 communication error. Double check even if you’re sure!

Identifying an issue with the Wire

Check the wire between the indoor and outdoor unit. Is it a single piece of wire with NO splices of any kind between them? Is it a 14GA stranded cable? If there are splices or it is a solid cable, either condition must be corrected.

Disconnect the wire from both ends. Separate the four conductors from each other and check them with an Ohm meter wire to wire. OL should show on the meter display. Set the meter to AC volts. Check for AC voltage between each of the four conductors. You shouldn’t have more than about 10 volts. If your induced voltage is higher than that, you may need to change to a shielded communication cable. BX style cable (below) can also be the cause for induced voltage on your communication wire. Bryant doesn’t recommend this style of wire.

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