Rick's Free Auto Repair Advice

Ford truck defrost only

Ford truck defrost only fix

If you own any of the Ford trucks listed below with the 7.3L or 6.0L diesel engine and find that you have a Ford truck defrost only situation where you can’t get the HVAC system to move to any other position, this is the fix you’re looking for.

Ford technical service bulletin 05-17-4

Ford has issued a service bulletin 05-17-4 to address a Ford truck defrost only condition on the vehicles listed below. Diesel engines don’t produce manifold vacuum because they don’t use a traditional throttle body, so the engines have a separate vacuum pump to generate a vacuum.
These trucks have a vacuum actuator to switch the HVAC system between modes, like from dash to defrost.

Ford vacuum pump in these vehicles my fail to run or may run continuously. If the pump doesn’t run, it won’t create vacuum and the HVAC actuators will default to the DEFROST position, giving you a Ford truck defrost only condition. In addition, a failed vacuum pump won’t provide the vacuum needed to actuate the 4WD function

Vehicles affected by Ford technical service bulletin 05-17-4

1999-2006 F-Super Duty
2000-2005 Excursion
1999-2006 F-650, F-750

Fix for Ford truck defrost only

Replace the vacuum pump with an updated model, part 6C3Z-2A451-BA



6C3Z-2A451-BA 2

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Posted on by Rick Muscoplat

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