Viessmann · Mini-split
J8 AC voltage protection
What the control is telling you
Supply voltage out of range. Shown on the 48K high heat model.
Applies to: DLCMHBH48EAK (48K high heat) only
Test and repair steps
- Safety kill power at the disconnect and wait for the inverter capacitors to discharge before touching boards or wiring.
- Measure supply voltage L1-L2 at the outdoor unit: about 187-253 VAC is acceptable.
- Measure DC across P and N on the IPM board: 277-356 V for 18-27K, 277-410 V for 36-48K.
- On 2-3 zone units also check DC across the bridge rectifier + and -: 190-250 V is normal.
- If the supply is good, replace parts in this order and retest: bridge rectifier (4-5 zone units), IPM board, outdoor main board.
Models that show this code
7 models in Viessmann Vitocal 200-S DLCM(R/H)B multi-zone outdoor
Other codes on the same units
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Source: DLCMRBH/DLCMHBH Multi-Zone Outdoor Service Manual (sold as Midea, Carrier and Viessmann Vitocal 200-S; Viessmann doc 6225551-03, 12/2024), Table 24 Outdoor Unit Error Display (48 High Heat only) p.27; diagnosis p.52-55. Summarized in our own words; check the original manual for your model.
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