EL18XC1

Outdoor HPS opened — coil circuit is dead. Not an inverter pressure fault and not an L-code.

1. 1 Let it cool, then read the drive LED

   On Lennox EL18XC1 overcurrent / overheat is often a dirty coil, a failed OD fan, or a locked compressor — not a dead inverter. Clear airflow, confirm the OD fan, and read the drive LED before you order a control. HPS continuity, reset if manual, wiring in series with the coil.

   Expect: OD fan running. Coil clean. Drive LED decoded from THIS outdoor’s card.

2. 2 Voltage and compressor windings

   Incoming voltage in range (this plate’s line-voltage code). Compressor windings even, no ground. A shorted compressor will kill a new drive. Outdoor airflow: dirty coil, bent fins, fan not running (see ODF / cap).

   Expect: Balanced windings. No winding to ground. Line voltage stable under load.

3. 3 Charge and the drive last

   A starved or flooded compressor will overcurrent. Confirm SH/SC and charge weight. Only then condemn the inverter. Overcharge or non-condensables — confirm indoor metering before you recover (SH vs SC).

   Expect: Charge on the nameplate. Drive code gone after a cool-down and a clean coil.

Fan not turning. Compressor may still run and then HPS.

1. 1 Heat rejection first

   On Lennox EL18XC1 high pressure is outdoor airflow until proven otherwise. Fan running the right direction, coil clean, fins not folded, no recirc over a fence or through a garage. Dual-cap FAN section µF vs sticker. A good HERM and a dead FAN is the usual Comfort call.

   Expect: OD fan on, coil clean, discharge air leaving the top/side freely.

2. 2 Head, subcooling, and liquid line

   Liquid pressure and liquid-line temperature → SC. High head + high SC = overcharge or non-condensables. High head + low SC = restriction or a dying compressor. Do not add gas because suction is low. Fan motor ohms / ground, blade clearance, capacitor wiring (C / FAN / HERM).

   Expect: SC vs the metering device on this plate (TXV ≠ piston).

3. 3 Restriction vs the switch

   Drier, liquid-line kink, TXV inlet screen, or a non-feed indoor coil will stack head. Ohm / jumper-test the HPS only as a momentary prove, then restore it. A switch that opens on a known-good charge and clean coil is the switch. Not an inverter fan module — there isn’t one.

   Expect: HPS closed at a normal liquid pressure for this refrigerant and OD ambient.

Will not pull, chatters, or is welded.

1. 1 Is Y actually at the contactor?

   On Lennox EL18XC1 a silent outdoor is often no Y. Measure 24 VAC coil-to-C at the contactor on a cool call. 24 VAC at the coil under a Y call. Low voltage = long stat wire, weak indoor transformer, or a furnace 24 (fuse) problem.

   Expect: ~24 VAC at the coil when the indoor is calling.

   If fail: Indoor Y / IFC / stat — not a capacitor.

2. 2 Cap and the compressor windings

   Dual run cap: herm and fan MFD ±6%. Then windings. A bad cap with a good Y is still the first cheap part — but confirm MFD, do not guess. Coil ohms / burned turns. Pitted or welded points — replace, do not file and leave.

   Expect: MFD on the can. Even windings. Fan and compressor both try.

3. 3 Contactor and mechanical

   Pitted contactor, no mechanical close, or a welded contactor that never drops out. Replace the failed part; do not file contacts as a repair. Chatter: low 24V, bad coil, weak transformer — not an inverter ramp.

   Expect: Clean pull-in. Line voltage through to both loads.

HERM and/or FAN section out of rating. Single-stage Comfort dies this way all summer.

1. 1 Is Y actually at the contactor?

   On Lennox EL18XC1 a silent outdoor is often no Y. Measure 24 VAC coil-to-C at the contactor on a cool call. Both sections vs microfarad rating, not just one.

   Expect: ~24 VAC at the coil when the indoor is calling.

   If fail: Indoor Y / IFC / stat — not a capacitor.

2. 2 Cap and the compressor windings

   Dual run cap: herm and fan MFD ±6%. Then windings. A bad cap with a good Y is still the first cheap part — but confirm MFD, do not guess. Bulged can, open bleed, wrong replacement (single vs dual, voltage).

   Expect: MFD on the can. Even windings. Fan and compressor both try.

3. 3 Contactor and mechanical

   Pitted contactor, no mechanical close, or a welded contactor that never drops out. Replace the failed part; do not file contacts as a repair. Hard-start add-ons do not fix a dead FAN section.

   Expect: Clean pull-in. Line voltage through to both loads.

Wrong charge method is as common as wrong charge.

1. 1 Airflow and freeze before you add gas

   On Lennox EL18XC1 low pressure / freeze is indoor airflow or a starved coil until proven otherwise. Filter, blower, dirty A-coil, closed supplies. In heat mode, a iced outdoor coil is the same family. Indoor piston: charge by superheat. Indoor TXV: charge by subcooling.

   Expect: Indoor air moving. Coil not iced. OD coil clear in heat.

2. 2 SH / SC after a thaw

   Thaw fully. Then SH and SC vs the metering device. Low charge ices a piston. A TXV stuck closed ices with high SH. A restriction downstream of the ports fakes a low-charge chart. Do not use Greenspeed weigh-in-only as the only method unless the factory TXV rating plate on THIS outdoor says so. Most 24ACC are piston/TXV conventional.

   Expect: SH/SC in range for this refrigerant and device after a stable 10-minute run.

3. 3 Leak, TXV, then the LPS

   Weigh-in if the chart says undercharge. Soap / electronic leak on joints and the coil. LPS that opens on a known-good charge and a clear coil is the switch — momentary test only, then restore. Line-set length and indoor coil match still matter. Weigh-in after a repair, then finish on SH or SC.

   Expect: Charge on the nameplate. LPS closed at a normal suction for this OD ambient.