Question about 1998 GMC Safari

2 Answers

98 Safari vent selection failure

Vent selection stuck on Defrost, selector knob rotates but air flow stays to defrost vents. Posible vaccum hose leak or disconnect? How do I locate where and which hose to check/replace?

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Along the fire wall follow the vacuum line. it is very small 3/32? and made of plastic which deteriorates over time. best to buy a rubber piece that fits over the plastic and link the two pieces together

Posted on Oct 25, 2008

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You're right commuter, it is a vacuum hose leak or disconnect.

start from the selector switch. take the bundle of hoses at the back of the controller and feel if there is a vacuum source.( the engine should be idling).

if there is then it could be a faulty selector.

if there is none. trace the hose that went outside of the firewall.

that is the vacuum source and you should be able to trace it to a vacuum tank. look for broken hoses or rusted tank.

good luck

tnx 4 using fixya,

drcool

Posted on Sep 13, 2008

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Air Flow Control
Air flow control is accomplished in the following manner:
  • Primary control is through the function selector knob , mounted on the heater function selector switch, which is part of the heater control .
  • The function selector knob has the following positions: OFF, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST.
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  • An internal single-pole electrical switch is also controlled by the selector. The switch controls the electrical supply to the heater blower motor switch (18578) .
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