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249 VAN Launch Kit 249 VAN Consumer Brochure Smart Thermostat Sell Sheet 249 VAN Launch Kit

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This installation was on a 4-story home, and the tech had not yet gone to the basement to troubleshoot the “infinity” water source heat pump, as he was told he by the homeowner. He was in the attic at the infinity furnace above the 4th floor. He was getting his dcv in the proper range on his A and B green plug on the air handler, 3 to 4 vdc. His indoor board ohm reading was in range, 28k to 32 k. The tech ohmed out the A and B thermostat wires on the water source heat pump from the upstairs. His ohm reading was not in range of a normal infinity board. His reading was around 64.4k. The tech then made the long walk to the basement where the “geothermal heat pump” was located. Bingo. 

Blue electronic circuit board with many wires and components inside a device enclosure
Close-up of a blue circuit board with green terminal block, resistors, and a gray connector plugged in.
Close-up of electrical wiring and connectors inside a device, with bundled red, blue, and black cables.
Close-up of a black electronic panel with a wiring diagram label and screwdriver pointing at it.
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Jonathon Pullen

Technical Services Manager Gulf Coast District

August 9, 2022

The Infamous E1: Part 2

E1 fault code on Ductless equipment is communication fault between the indoor and outdoor units.


When the E1 code shows up on the indoor display board, the coms have failed and the systems have stopped working. Until this problem is fixed, the system will remain off.


Start trouble shooting this problem at the outdoor by taking a DCV reading on L2 and S or 2 and 3 depending on how the unit is labeled. Take a DCV reading on the terminals for the indoor unit wires. Good coms volts look like + to – 50 volts fluctuation.

Electrical wiring terminal block inside an appliance, with colored wires and a hand holding red probes.
Digital multimeter showing 30.21 beside a wiring terminal block, with red and black test probes attached.

If you see a fixed negative or a small amount of fluctuating volts staying in the negative, the indoor board has failed.


If you see a fixed positive volt reading or a fluctuating positive reading the outdoor board is bad.



The reactor also needs to be checked. Check the reactor with the wires off and ohm it out. The ohm reading should be .1-1 ohm and should not be grounded.

Blue-lit digital multimeter showing 3.033 V DC with black and red probes connected
Yellow digital multimeter with red and black probes measuring wiring in an electrical panel; display shows 74.0V
Coiled black toroidal inductor with copper windings and white insulated leads on a wood surface
Yellow clamp meter with coiled current probe and red/black test leads on a dark surface, showing 0.0
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249 VAN Launch Kit 249 VAN Consumer Brochure Smart Thermostat Sell Sheet 249 VAN Launch Kit

Unlock the Full Potential

View Quick Start Guide

This installation was on a 4-story home, and the tech had not yet gone to the basement to troubleshoot the “infinity” water source heat pump, as he was told he by the homeowner. He was in the attic at the infinity furnace above the 4th floor. He was getting his dcv in the proper range on his A and B green plug on the air handler, 3 to 4 vdc. His indoor board ohm reading was in range, 28k to 32 k. The tech ohmed out the A and B thermostat wires on the water source heat pump from the upstairs. His ohm reading was not in range of a normal infinity board. His reading was around 64.4k. The tech then made the long walk to the basement where the “geothermal heat pump” was located. Bingo. 

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