Antminer KA3 – Temperature Too High

Power off at the breaker, wait 15 minutes. A hot KA3 sensor reads inflated; let it cool before you do anything else. This alone will often clear a single-shot `ERR_TEMP_HIGH` that was a transient ambient spike.

Clean the intake grille and fin stacks with compressed air. Take the miner outside or over a tarp. Blast both fans, both intake sides of the fin stack, and the exhaust. Dust falls out in sheets on a neglected KA3. Do not use a shop-vac in suction mode on an unpowered miner — static can kill the PIC. Compressed air only. Budget 15 minutes and go thorough.

Verify ambient ≤ 30 °C at the intake. IR thermometer at the front grille, not in the middle of the room. If the miner is in a closet, on a shelf, or against a wall, the intake can be 5-10 °C hotter than the rest of the room because exhaust recirculates. Either move the miner or add forced-air exhaust.

Restart and monitor for 30 minutes. Watch dashboard chain temps and RPMs. If all three chains settle under 70 °C chip / 75 °C PCB and fans hold under 95% duty, you fixed it. If it trips again — move to Tier 2.

Check for a firmware update at `support.bitmain.com/downloads`. If a known-buggy temperature-threshold build is on your miner, roll one version back. Verify the hardware revision against the firmware notes before flashing — wrong firmware on a late-rev control board is a separate disaster.

Re-seat every hashboard data and power cable. Power off at the breaker first. Disconnect, inspect pins for blackening/corrosion, reconnect firmly until you feel the click. Oxidation on data connectors raises communication error rate, and the controller sometimes defensively throws `ERR_TEMP_HIGH` when it can't trust a board's readings.

Swap hashboards between slots. Label slots 0/1/2 with tape. Move the hottest-running board to a known-good slot. Observe for 30 minutes. If the hot temp follows the board, the board is the problem (paste, fin contamination, failing chip). If the hot temp stays in the slot, your chassis airflow in that zone is compromised — check the fan feeding that slot.

Swap fans. KA3 fans are 12 V, 4-wire PWM axial. Verify the exact form factor on your batch (common: 12038 or 12025) before ordering. Install known-good fans, reboot, re-observe. If the overheat clears, your old fan was the fault even if RPM looked "close enough" on the graph.

Measure PSU output under load. Multimeter on DC, probe at the PSU-to-board connector while the miner is hashing. Healthy KA3: ≥ 13.8 V sustained on the hashboard rail under full load. Sagging PSU pushes chip power dissipation up for the same hashrate, which shows as temperature creep. Swap the PSU with a known-good APW12 if in doubt.

Line voltage check at the panel. 235-245 V on 240 V split-phase; 202-212 V on 208 V commercial. Low line voltage under load = PSU compensates with more current = more heat generated at the PSU and at the hashboard voltage domain. If you're on 110 V: you're on the wrong voltage for a KA3, full stop — a KA3 on 110 V will either undervolt-trip or overheat constantly.

Refresh thermal paste on all three hashboards. Remove heatsinks, clean old paste with 99% IPA and lint-free wipes until the BM1074 die and heatsink base are mirror-clean. Apply Arctic MX-6 or Thermal Grizzly Kryonaut in a thin, uniform layer — no glop, no dome, no X-pattern theatre. The BM1074 is a single-die package, so pressure distribution matters more than geometry. Reinstall heatsinks with even torque, no overtightening. Expect a 5-10 °C drop at the same load on a miner whose paste was dried-out.

Inspect and replace thermal pads on PCH / voltage-domain ICs. Beside the ASICs, the KA3 hashboard has secondary thermal pads bridging the PCH and voltage-domain ICs to the heatsink frame. These crumble faster than the ASIC paste because they run hotter with less margin. Replace with equivalent-thickness 3M, Arctic, or Thermal Grizzly pads — match the original thickness exactly, not "close enough."

Cross-flash DCENT_OS for per-chip thermal visibility. [DCENT_OS](https://d-central.tech/dcent-os/) is D-Central's own open-source Antminer firmware — all the per-chip temperature, HW%, tuning, autotuning, and stratum v2 features of the commercial third-party firmwares, open-source, Mining-Hacker-maintained, no licensing BS. [Source on GitHub.](https://github.com/DCentralTech/DCENT_OS) Alternatives if you prefer: Braiins OS+, LuxOS, or Vnish. All four surface per-chip temps that stock Bitmain firmware hides behind chain-level rollups. Once flashed, let the miner stabilize for 20 minutes and identify chip positions running hot relative to their neighbours. A single hot chip points at a paste/heatsink-contact issue at that position; an entire hot zone points at board or fan airflow.

Reflash the PIC chip (if `fail to read pic temp` was the trigger). This requires a PIC programmer (PICkit 4 or equivalent), the correct Bitmain PIC firmware image for your KA3 hardware revision, and a steady hand on the ISP pads. Not a first-time soldering project. If you've never reflashed a PIC before, skip to Tier 4.

Roll firmware to the last-known-good version for your exact hardware revision. Pull your build date off the control board sticker or from the `miner status` page; match it against Bitmain's firmware compatibility notes; flash accordingly. Wrong firmware on a late-rev board = bricked control board = Tier 4.

Stop DIY when: paste refresh + fan swap + PSU swap + firmware check all fail; per-chip temps isolate 3+ hot chips on one board (chip-level failure, not paste/fin); `fail to read pic temp` persists across slots and you don't have a PIC programmer on the bench. [Book a D-Central ASIC Repair slot.](https://d-central.tech/services/asic-repair/)

What the D-Central bench does: test fixture with programmable load, per-chip thermal imaging under controlled ambient, PIC reflash with official Bitmain binaries, paste/pad refresh using bench-grade materials, BM1074 chip replacement where one or more chips are genuinely dead, and a 24-hour post-repair burn-in at nameplate before it ships back to you.

Ship safely. Anti-static bag each hashboard, double-box with ≥ 5 cm foam on every side, include a note with observed symptoms, exact log strings, firmware version, and your contact info. Thorough notes cut diagnostic time, which cuts your repair invoice. Canada-wide shipping, US/international welcomed.