Wellington rail workers say they and the public are sick of having to endure cold conditions on the network's old trains and are taking action.
Heating on the 14 1940s English Electric trains was turned off two weeks ago as a precaution after one train over-heated, while a few others have only been half-heated for several years.
The trains are being replaced by the Matangi trains and will be out of use by July next year.
Rail and Maritime Transport Union general secretary Wayne Butson says the lack of heating is causing a lot of discomfort for commuters, with one guard receiving 70 complaints on a shift.
Workers have called a health and safety meeting next Tuesday and will consider banning using trains with no heaters, he says.
KiwiRail says heating will be restored to the old trains by July.
General manager for passengers Deborah Hume says the heating was turned off for safety reasons - not to cut costs - and will be restored in two stages.