1998 GMC Jimmy air conditioning not working

When you turn the air conditioning on--does the compressor kick in? It sounds like you have a blend door actuator that is not working,

Here is a guide to help you fix it.

https://www.2carpros.com/articles/replace-blend-door-motor

Let me know how ti goes.

yes he does,with the air conditioning on,,off the vents send only hot air.

Is your answer " yes the compressor kicks on and the vents blow hot air" ?

Hello , thank`s for help me,, yes the vents send only very hot air not warm not cold only hot air,.
the most cars with the air conditioning in off ,send cold air in winter time ,my truck send me only very hot air , does not matter if I put the a/c automatic control in cold or in warm,hot.

I am assuming that the temperature selector switch is in the cold position and the blower only blows hot air--right?
Your heating and air conditioning systems are two totaly different systems. Your heating system relies on engine temperature to heat the coolant that flows through your heater core. Then the blower blows air right through the heater core and into the cars' cabin.
Your air conditioning system works a little different. There is a compressor that is driven by a belt mounted on the front of your motor. When you turn on the A/C switch this activates a clutch that is connected to the compressor. When activated (or kicked on) the compressor compresses refrigerant through the A/C system. To keep it simple--this refrigerant flows through the A/C system and extracts heat from the cars' cabin and replaces hot air with cold air.
The A/C system has no connection with the heating system. The pressure and amount of refrigerant ( R-134) is important. You need an A/C system pressure gauge to measure the R-134 in the system.
However it sounds like --to me-- that your problem is the temperature control switch. The switch I am talking about is right next to the fan speed switch. It has a setting that goes from "red" to "blue". Red meaning hotter and blue meaning colder. I think this switch may be broken...

I am assuming that the temperature selector switch is in the cold position and the blower only blows hot air--right?


YESSSS !!!! you think the switch was broken after flushing system..coolant.,heater core ..etc.

i will change the switch i be back :)
thank`s

Hello ,i changed temperature control switch , still sending hot air from te vents :( everything start when my heater not work,then i flush the system new coolant in the radiator etc. after i flush the system i get only hot air i move the control to (blue meaning colder ,the vents sends only hot air.

Let me try to help,
The temperature switch controlls a vaccum or cable linked door that diverts air through either your heater core (for heat) the a/c evaporator (for cold) or both ( for warm air) . Look around the ventilation duct (the housing that runs from the blower to the vents) for any disconnected vaccum hose or cable that may come off during the time you serviced the heater core. I am almost certain thats the problem...larry