Customer Service Advice

I run a mobile PC repair business. I recently had a housecall with a customer who’s PC appeared to have a bad power supply. I put in a new PS and everything worked just fine. However, as soon as I put the cover back on the case and powered up, the new power supply got that ugly burnt electrical smell and the PC was dead again. My conclusion was that there was a short in the case. I oferred to rebuild the system in a new case but could not guarantee there would not be other issues. The customer wanted to think about that before committing. My real question here is: Is it appropriate to charge the customer for the new power supply that got burnt out as part of that service call, or should I just write it off and take the loss?