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AC Switch has Off and Full, Nothing in Between

Big T

Big T

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AC switch on the 1999 K2500 only works full on. None of the other speed settings work. What part do I need to replace?
 
Shotgun it... :p Seriously, it may be a failing blower motor that locks up (Stops spinning while still passing current) and the thermal fuses on the resister pack burn out. I would start by checking the resister pack.
 
3500GMC said:
Check the blower motor health. High amp draw will fry stuff.

Resistor sometimes takes the plug out with it.

Part pictured appears to be the plug and pigtail assembly.
Click to expand...

Yeah, If the resister pack is "bad" NQA: replace the blower motor. (Aka Shotgun parts at it.) Also inspect for foreign objects that may be jamming it including plugging evaporator or intake airflow completely up. Note AC Delco blower motors are quiet vs. the noisy ticking aftermarket Commie cheap ones.
 
The resistors can be tested with an ohm meter, IIRC.
Should be different resistance ratings for each terminal.
Fuses can be tested with an ohms meter too, a lead into each end of the fuse and see that it reads zeros, meaning there is 0 resistance.
 
WarWagon said:
Yeah, If the resister pack is "bad" NQA: replace the blower motor. (Aka Shotgun parts at it.) Also inspect for foreign objects that may be jamming it including plugging evaporator or intake airflow completely up. Note AC Delco blower motors are quiet vs. the noisy ticking aftermarket Commie cheap ones.
Click to expand...
Not true on the blower motors. I spent the extra coin for a genuine oem blower motor, less than 2 years later and I can't stand to listen to the noise on the 2 slow fan speeds. The cheap blower motors I put in from the parts stores all held up better.
 
As much trouble as it is to get to the blowet resistor, you better just go ahead and put a new one in there. The 97+ dash with passenger airbag may be easier to get to, but I know 95-96 is almost impossible to get to it. Blower switches also fail, so much so, GM had a TSB out for them. Obviously check your fuses as high fan speed used it's own seperate power supply from the other speeds, so make sure all fuses are good. The blower resistor is buried behind the glove box, towards the center of the vehicle, on top of the evap box, behind the 3 relays for the hvac controls.
 
THEFERMANATOR said:
As much trouble as it is to get to the blowet resistor, you better just go ahead and put a new one in there. The 97+ dash with passenger airbag may be easier to get to, but I know 95-96 is almost impossible to get to it. Blower switches also fail, so much so, GM had a TSB out for them. Obviously check your fuses as high fan speed used it's own seperate power supply from the other speeds, so make sure all fuses are good. The blower resistor is buried behind the glove box, towards the center of the vehicle, on top of the evap box, behind the 3 relays for the hvac controls.
Click to expand...

This is on the '99. Is the resistor behind the AC dial knob?
 
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