1998 GMC Sierra pickup truck cabin fan problem

My air conditioner on my Buick has a full charge of Freon and when it is hot out I don't get the cooling power in the cabin as I have it on low switch so when I put the switch on the high the Air doesn't change to cool the interior on high. I had the Freon tested and it still doesn't work properly and I wonder if there is a sensor that doesn't allow the system to cool properly?

I would suspect a stuck cooling fan relay. Your going to have to locate the malfunction to get the operation that you seek. Reference owners manual for lcoation of the cooling fan relay and try switching it out.

If air is hot then cold it sounds like you have a sizable air pocket in the cooling system. This could be caused by a leak or if you have recently done anything to the system without bleeding it afterward.

My 1992 gmc pickup keeps blowing heater fuses I have replaced blower motor can you help me jody.

Check the fuses and relays for heater and AC. If good , a fusible link wire could have burned out.

Two possible problems. First the Freon level might be too low to allow the low pressure protection switch from letting electricity get to your compressor's clutch. This is just a 'most likely' reason, there can be others.

But then you definitely have a problem with the heater resistor pack that is mounted in the heater's air stream somwhere behind the glove box. This device allows for low, and medium fan speeds but needs to be cooled or else it will melt and open up electrically. When that happens you 'loose' fan speeds except for high which is 12 volts direct to the heater motor.

This year GM pickups needed the HEPA air filter but did not have one so that all manner of hay trash, leaves and you name it would plug up the air conditioner evaporator inside the cab which in turn stopped enough air flow to the heater resistor pack which causes it to fail and you wind up with no DOT required defroster AND carbon monoxide preventing air flow into the cabin. There is law and how they avoided a class action suit is beyond me but you are looking at about a hundred dollars to replace the resistor pack and heater switch too.

You might have minimum success blowing the trash out of the evaporator backwards after you take it all apart, as a passenger when you kick the 'heater', that is right where you need to go to clean out the evaporator. It's only 1/2 inch thick and on the bottom of the pile.

If you have good air flow on high then you can disregard the blowing out of the evaporator and just concentrate on getting to the resistor pack - we just changed it with the switch panel to get it all done with in one shot. There is an outside chance that fixing the resistor pack/switch will return your compressor's voltage as well, there is no telling how that switch has it's failsafes integrated.

It sounds like you either have an condensor fan problem or low freon. The condensor fan is near the radiator. In some cases the radiator fan doubles as the condensor fan. So look there too.

open glove box and make sure that none of the papers from that can get down to blower motor

http://www.fixya.com/cars/t1386554-91_ford Please read this post, I hope it will help you.

Possibly fan clutch or clogged radiator/condensor.
To check for fan clutch, hook up A/C gauges, turn a/c on watch high side gauge. 300 psi. and above run water on condensor, if psi. goes down to about 250 psi and holds. replace fan clutch.
If not, check radiator/condensor for dibris outside, and or corrosion inside the radiator.