"They had to go and swap it back to have a truck that works basically," he said.
The other truck is 25 years old and Moore said it had been sent to the mechanic to repair faults like a broken temperature gauge and having no illumination on the dashboard, which was not able to be done before it was needed again on Monday.
Once it was repaired, the 32-year-old truck would be back in service as there were no spare trucks for the crews to use.
Moore said it was an example of the state of the nationwide fleet and it was unacceptable Fire Emergency NZ (FENZ) had let the fleet of fire trucks, both in Whanganui and nationwide, get into such disrepair.
"They've let the fleet get to this state, it's quite disgraceful really, for our safety and the public.
"We just want tools to do our job [with], and you see it nationwide, trucks breaking down while on fire calls and emergencies which isn't really acceptable, especially in life-threatening situations."
FENZ region manager Bruce Stubbs said there were more than 1240 fire trucks and specialist vehicles in the national fleet.
"In any large vehicle fleet like ours, from time to time it is expected there may be issues.
"That's why our vehicles are serviced regularly, and we have plans in place to cover trucks that may be out of service," he said.
Whanganui Fire Station had nine trucks of various types, ranging in age from 3 to 32 years old, Stubbs said.
"Having trucks of different ages is part of a normal asset life cycle for a large fleet like ours."
He said FENZ had an ongoing programme which involved purchasing new trucks and disposing of old ones, and trials were under way for a new version of the type of truck on which the pedal broke.
"At this stage, a specific date has not been set for Whanganui Station to receive a new fire truck," Stubbs said.
NZPFU and FENZ have been in negotiations for the last 17 months, with NZPFU members arguing for better pay, updated equipment and better support for their physical and mental health among other issues.
In August, NZPFU members across the country, including in Whanganui, went on strike for one hour on two Fridays
NZPFU has announced a new round of strikes will be held between 11am and midday bi-weekly from Friday, November 4.