Prior to February values had risen for three months in a row.
Average age in March remained static at 52 months while mileage rose by 1139 to 76,263 miles.
Year-on-year values in March were down 6.9%.
Large panel vans weighing more than 3.0 tonnes fell by 2.5% to £4054 in March and 4x4s dropped 4.5% to £7686.
On the other hand car-derived vans grew in value by 1.5% to £2773, small vans were up 4.7% to £4035 and medium-sized vans increased by 4.2% to £3888.
Most price fluctuations related to changes in age and mileage, said Manheim.
