Staff picketed in Platts Common on Wednesday and support for the action was evident, with locals delivering food and drink to those attending.
Ambulance workers are asking for a pay rise above inflation - although not a precise figure - and a plan for recouping lost earnings over many years.
The GMB, Unison and Unite unions are coordinating the industrial action, calling for a pay increase for workers.
But they say this isn’t just about money - it’s also about making a stand to protect the ‘crumbling’ NHS.
NHS medical director professor Sir Stephen Powis, said: “There is no doubt that the NHS is facing extreme pressure and industrial action will add to the already record demand we are seeing on urgent and emergency care, and so it is really important that the public play their part by using services wisely.
“This means continuing to call 999 for life-threatening emergencies - if it is not life-threatening you may have to wait longer than usual for an ambulance.
“NHS staff have worked hard to minimise disruption but it is inevitable as with any industrial action that we will see an impact on services but it is vital if you need lifesaving care, to continue to come forward.”