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1978 Mark V Blower Motor Issues

Hey Bill,

Just purchased a '78 Mark V and it has many problems.

One of which are the Door Lock Actuators, which I have ordered from Lincoln Land. However, another one has me stumped. The Blower Motor works on all speeds on every selection on the controls, except the heat selection. Have tried replacing the A/C - Heat controls and the same happens. This car has auto temp control. Any ideas would help.




Hello Larry -

Congratulations on your recent purchase and we are pleased to have you as our customer. The problem of no blower operation in the heat selector position is caused 99% of the time by the failure of a part known as the Electro Vacuum Relay module which is located under the dash and up to the right of the transmission hump area. This unit is part of the blower delay feature that delays blower operation until the engine coolant warms up when the selector is positioned in the HEAT position. It is easily removed and replaced. The Shop Manual shows the location and as well explains the operation. Of course there is always an exception but as stated above this issue is 99% of the time caused by an electrical failure within this relay.