Vandals have smashed the back window of a St John Ambulance vehicle the day before the Tamworth branch were set to volunteer at the Tamworth Baseball June Long Weekend Carnival.
It is the second time in the last few months that a window has been smashed on the vehicle. In April, the rear window was smashed and the ambulance was then ransacked.
Both incidents have been reported to the police.
While the volunteers had enough time to clean up the mess and cover the window so rain didn't run into the vehicle, St John's Robyn Perry said it was lucky there wasn't an emergency.
"You never know when we'll have an emergency and if we get in the vehicle and find something missing or something's been stolen, hopefully it's not your family we have to help," she said.
She added: "There's no point in it.
"There was electrical wires exposed yesterday [Friday]."
The St John vehicles don't have a permanent home and the volunteers are asking for help from the community.
"The main thing [now] is trying to find somewhere safe for the vehicles," Ms Perry said.
Fellow St John volunteer Margaret O'Connor added: "I'm even happy if it's not undercover. If it's just in a secure location, a secure yard, we'd still have access to [we'd be happy]."
The volunteers said if there was anyone out there willing to house the St John vehicles, or anyone looking to volunteer for St John, to contact Margaret O'Connor on 0409 307 782 or email@example.com.