In this court-tried case plaintiff trailer home owners got judgment against defendant appliance dealer for the $1,762 they had paid for an installed combination air-conditioning and heating system.

Plaintiffs pleaded and their expert evidence showed that although the unit was *632mechanically sound it was not the type designed for a house trailer and utterly failed to either cool or heat. Plaintiffs’ evidence was that defendant made several mechanical adjustments and installed larger duct-work, all to no avail. Finally plaintiffs replaced the original unit with a proper one and sued for refund of their original purchase price.

Defendant now contends the judgment lacks sufficient evidence. He argues that the testimony of plaintiffs’ expert witness showed the unit was mechanically sound, but that misses the point because the witness further testified the unit sold was the wrong type of appliance for a house trailer. Defendant testified the problem could be solved by installing larger ductwork, which he did; plaintiffs testified the unit still would not adequately cool or heat. Defendant also relies on a letter plaintiffs wrote saying the air conditioning unit “has sufficient air circulation.” Plaintiff acknowledged this but explained: “It had the circulation but it brought in hot air.”

Defendant testified that without charge he and his employees made numerous service calls attempting to make the unit effective.

We have reviewed the case in accordance with Rule 73.01 3 and giving due regard to the trial court’s opportunity to judge the credibility of witnesses, we conclude the judgment is supported by substantial evidence. Lickting v. Goins, 458 S.W.2d 596[2] (Mo.App. 1970).

Judgment affirmed.